Topographic anatomy is an approach to anatomical study based on regions, parts, or divisions of the body (e.g., the foot
or the inguinal region), emphasizing the relationships of various systemic structures (e.g., muscles, nerves, and arteries)
within that area; distinguished from systemic anatomy.
Skeletotopia means position of an organ in relation to the elements of skeleton.
Holotopia means position of organ in certain part or cavity of the body, and projection of the organ on the regions of body
surface and the walls of body cavities.
Syntopia means relation of an organ to the adjoining organs and anatomical structures.
The Thoracic Cavity. The heart and lungs are situated in the thorax, the walls of which afford them protection. The heart
lies between the two lungs, and is enclosed within a fibrous bag, the pericardium, while each lung is invested by a serous
membrane, the pleura. The skeleton of the thorax, and the shape and boundaries of the cavity, have already been described
The capacity of the cavity of the thorax does not correspond with its apparent size externally, because (1) the space enclosed by the lower ribs is occupied by some of the abdominal viscera; and (2) the cavity extends above the anterior parts
of the first ribs into the neck. The size of the thoracic cavity is constantly varying during life with the movements of the ribs
and diaphragm, and with the degree of distention of the abdominal viscera. From the collapsed state of the lungs as seen
when the thorax is opened in the dead body, it would appear as if the viscera only partly filled the cavity, but during life
there is no vacant space, that which is seen after death being filled up by the expanded lungs.
The Upper Opening of the Thorax. The parts which pass through the upper opening of the thorax are, from before backward, in or near the middle line, the Sternohyoideus and Sternothyreoideus muscles, the remains of the thymus, the inferior
thyroid veins, the trachea, esophagus, thoracic duct, and the Longus colli muscles; at the sides, the innominate artery, the
left common carotid, left subclavian and internal mammary arteries and the costocervical trunks, the innominate veins, the
vagus, cardiac, phrenic, and sympathetic nerves, the greater parts of the anterior divisions of the first thoracic nerves, and
the recurrent nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little
above the level of the sternal end of the first rib.
The Lower Opening of the Thorax. The lower opening of the thorax is wider transversely than from before backward. It
slopes obliquely downward and backward, so that the thoracic cavity is much deeper behind than in front. The diaphragm
closes the opening and forms the floor of the thorax. The floor is flatter at the center than at the sides, and higher on the
right side than on the left; in the dead body the right side reaches the level of the upper border of the fifth costal cartilage,
while the left extends only to the corresponding part of the sixth costal cartilage. From the highest point on each side the
floor slopes suddenly downward to the costal and vertebral attachments of the diaphragm; this slope is more marked behind
than in front, so that only a narrow space is left between the diaphragm and the posterior wall of the thorax.
The cavity of the mouth is placed at the commencement of the digestive tube; it is a nearly oval-shaped cavity which consists of two parts: an outer, smaller portion, the vestibule, and an inner, larger part, the mouth cavity proper.
The Vestibule (vestibulum oris) is a slit-like space, bounded externally by the lips and cheeks; internally by the gums and
teeth. It communicates with the surface of the body by the rima or orifice of the mouth. Above and below, it is limited by
the reflection of the mucous membrane from the lips and cheeks to the gum covering the upper and lower alveolar arch
respectively. It receives the secretion from the parotid salivary glands, and communicates, when the jaws are closed, with
the mouth cavity proper by an aperture on either side behind the wisdom teeth, and by narrow clefts between opposing
teeth.
The Mouth Cavity Proper (cavum oris proprium) is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the pharynx by a constricted aperture termed the isthmus faucium. It is roofed in
by the hard and soft palates, while the greater part of the floor is formed by the tongue, the remainder by the reflection of
the mucous membrane from the sides and under surface of the tongue to the gum lining the inner aspect of the mandible. It
receives the secretion from the submaxillary and sublingual salivary glands. The mucous membrane lining the mouth is
continuous with the integument at the free margin of the lips, and with the mucous lining of the pharynx behind; it is of a
rosepink tinge during life, and very thick where it overlies the hard parts bounding the cavity. It is covered by stratified
squamous epithelium.
The Lips (labia oris), the two fleshy folds which surround the rima or orifice of the mouth, are formed externally of integument and internally of mucous membrane, between which are found the Orbicularis oris muscle, the labial vessels, some
nerves, areolar tissue, and fat, and numerous small labial glands. The inner surface of each lip is connected in the middle
line to the corresponding gum by a fold of mucous membrane, the frenulum - the upper being the larger.
The Labial Glands (glandulœ labiales) are situated between the mucous membrane and the Orbicularis oris, around the
orifice of the mouth. They are circular in form, and about the size of small peas; their ducts open by minute orifices upon
the mucous membrane. In structure they resemble the salivary glands.
The Cheeks (buccae) form the sides of the face, and are continuous in front with the lips. They are composed externally of
integument; internally of mucous membrane; and between the two of a muscular stratum, besides a large quantity of fat,
areolar tissue, vessels, nerves, and buccal glands. The mucous membrane lining the cheek is reflected above and below
upon the gums, and is continuous behind with the lining membrane of the soft palate. Opposite the second molar tooth of
the maxilla is a papilla, on the summit of which is the aperture of the parotid duct. The principal muscle of the cheek is the
Buccinator; but other muscles enter into its formation, viz., the Zygomaticus, Risorius, and Platysma.
The buccal glands are placed between the mucous membrane and Buccinator muscle: they are similar in structure to the
labial glands, but smaller. About five, of a larger size than the rest, are placed between the Masseter and Buccinator mus-
cles around the distal extremity of the parotid duct; their ducts open in the mouth opposite the last molar tooth. They are
called molar glands.
The Gums (gingivae) are composed of dense fibrous tissue, closely connected to the periosteum of the alveolar processes,
and surrounding the necks of the teeth. They are covered by smooth and vascular mucous membrane, which is remarkable
for its limited sensibility. Around the necks of the teeth this membrane presents numerous fine papillae, and is reflected
into the alveoli, where it is continuous with the periosteal membrane lining these cavities.
The Palate (palatum) forms the roof of the mouth; it consists of two portions, the hard palate in front, the soft palate behind.
The Hard Palate (palatum durum) is bounded in front and at the sides by the alveolar arches and gums; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous membrane of the mouth,
which are intimately adherent. Along the middle line is a linear raphae, which ends anteriorly in a small papilla corresponding with the incisive canal. On either side and in front of the raphé the mucous membrane is thick, pale in color, and corrugated; behind, it is thin, smooth, and of a deeper color; it is covered with stratified squamous epithelium, and furnished with
numerous palatal glands, which lie between the mucous membrane and the surface of the bone.
The Soft Palate (palatum molle) is a movable fold, suspended from the posterior border of the hard palate, and forming an
incomplete septum between the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibers,
an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands. When occupying its usual position, i. e., relaxed and
pendent, its anterior surface is concave, continuous with the roof of the mouth, and marked by a median raphé. Its posterior
surface is convex, and continuous with the mucous membrane covering the floor of the nasal cavities. Its upper border is
attached to the posterior margin of the hard palate, and its sides are blended with the pharynx. Its lower border is free. Its
lower portion, which hangs like a curtain between the mouth and pharynx is termed the palatine velum.
Hanging from the middle of its lower border is a small, conical, pendulous process, the palatine uvula; and arching lateralward and downward from the base of the uvula on either side are two curved folds of mucous membrane, containing muscular fibers, called the arches or pillars of the fauces.
The Tongue (lingua) is the principal organ of the sense of taste, and an important organ of speech; it also assists in the
mastication and deglutition of the food. It is situated in the floor of the mouth, within the curve of the body of the mandible.
Its Root (radix linguae, base) is directed backward, and connected with the hyoid bone by the Hyoglossi and Genioglossi
muscles and the hyoglossal membrane; with the epiglottis by three folds (glossoepiglottic) of mucous membrane; with the
soft palate by the glossopalatine arches; and with the pharynx by the Constrictores pharyngis superiores and the mucous
membrane.
Its Apex (apex linguae, tip), thin and narrow, is directed forward against the lingual surfaces of the lower incisor teeth.
Its Inferior Surface (facies inferior linguae, under surface) is connected with the mandible by the Genioglossi; the mucous
membrane is reflected from it to the lingual surface of the gum and on to the floor of the mouth, where, in the middle line,
it is elevated into a distinct vertical fold, the frenulum linguae. On either side lateral to the frenulum is a slight fold of the
mucous membrane, the plica fimbriata, the free edge of which occasionally exhibits a series of fringe-like processes.
The apex of the tongue, part of the inferior surface, the sides, and dorsum are free.
The Dorsum of the Tongue (dorsum linguae) is convex and marked by a median sulcus, which divides it into symmetrical
halves; this sulcus ends behind, about 2.5 cm. from the root of the organ, in a depression, the foramen cecum, from which a
shallow groove, the sulcus terminalis, runs lateralward and forward on either side to the margin of the tongue. The part of
the dorsum of the tongue in front of this groove, forming about two-thirds of its surface, looks upward, and is rough and
covered with papillae; the posterior third looks backward, and is smoother, and contains numerous muciparous glands and
lymph follicles (lingual tonsil). The foramen cecum is the remains of the upper part of the thyroglossal duct or diverticulum
from which the thyroid gland is developed; the pyramidal lobe of the thyroid gland indicates the position of the lower part
of the duct.
The Papillae of the Tongue are projections of the corium. They are thickly distributed over the anterior two-thirds of its
dorsum, giving to this surface its characteristic roughness. The varieties of papillae met with are the papillae vallatae, papillae fungiformes, papillae filiformes, and papillae simplices.
The papillae vallatae (circumvallate papillae) are of large size, and vary from eight to twelve in number. They are situated
on the dorsum of the tongue immediately in front of the foramen cecum and sulcus terminalis, forming a row on either side;
the two rows run backward and medialward, and meet in the middle line, like the limbs of the letter V inverted. Each papilla consists of a projection of mucous membrane from 1 to 2 mm. wide, attached to the bottom of a circular depression of
the mucous membrane; the margin of the depression is elevated to form a wall (vallum), and between this and the papilla is
a circular sulcus termed the fossa. The papilla is shaped like a truncated cone, the smaller end being directed downward and
attached to the tongue, the broader part or base projecting a little above the surface of the tongue and being studded with
numerous small secondary papillae and covered by stratified squamous epithelium.
The papillae fungiformes (fungiform papillae), more numerous than the preceding, are found chiefly at the sides and apex,
but are scattered irregularly and sparingly over the dorsum. They are easily recognized, among the other papillae, by their
large size, rounded eminences, and deep red color. They are narrow at their attachment to the tongue, but broad and rounded at their free extremities, and covered with secondary papillae.
The papillae filiformes (filiform or conical papilae) cover the anterior two-thirds of the dorsum. They are very minute, filiform in shape, and arranged in lines parallel with the two rows of the papillae vallatae, excepting at the apex of the organ,
where their direction is transverse. Projecting from their apices are numerous filamentous processes, or secondary papillae
these are of a whitish tint, owing to the thickness and density of the epithelium of which they are composed, which has here
undergone a peculiar modification, the cells having become cornified and elongated into dense, imbricated, brush-like processes. They contain also a number of elastic fibers, which render them firmer and more elastic than the papillae of mucous
membrane generally. The larger and longer papillae of this group are sometimes termed papillae conicae.
The papillae simplices are similar to those of the skin, and cover the whole of the mucous membrane of the tongue, as well
as the larger papillae. They consist of closely set microscopic elevations of the corium, each containing a capillary loop,
covered by a layer of epithelium.
Muscles of the Tongue. The tongue is divided into lateral halves by a median fibrous septum which extends throughout its
entire length and is fixed below to the hyoid bone. In either half there are two sets of muscles, extrinsic and intrinsic; the
former have their origins outside the tongue, the latter are contained entirely within it.
The extrinsic muscles are: Genioglossus. Hyoglossus. Chondroglossus. Styloglossus. Glossopalatinus.
The Genioglossus (Geniohyoglossus) is a flat triangular muscle close to and parallel with the median plane, its apex corresponding with its point of origin from the mandible, its base with its insertion into the tongue and hyoid bone. It arises by a
short tendon from the superior mental spine on the inner surface of the symphysis menti, immediately above the Geniohyoideus, and from this point spreads out in a fan-like form. The inferior fibers extend downward, to be attached by a thin
aponeurosis to the upper part of the body of the hyoid bone, a few passing between the Hyoglossus and Chondroglossus to
blend with the Constrictores pharyngis; the middle fibers pass backward, and the superior ones upward and forward, to
enter the whole length of the under surface of the tongue, from the root to the apex. The muscles of opposite sides are separated at their insertions by the median fibrous septum of the tongue; in front, they are more or less blended owing to the
decussation of fasciculi in the median plane.
The Hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of
the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the Styloglossus and Longitudinalis inferior. The fibers arising from the body of the hyoid bone overlap those from the greater cornu.
The Chondroglossus is sometimes described as a part of the Hyoglossus, but is separated from it by fibers of the Genioglossus, which pass to the side of the pharynx. It is about 2 cm. long, and arises from the medial side and base of the lesser cornu and contiguous portion of the body of the hyoid bone, and passes directly upward to blend with the intrinsic muscular fibers of the tongue, between the Hyoglossus and Genioglossus.
A small slip of muscular fibers is occasionally found, arising from the cartilago triticea in the lateral hyothyroid ligament
and entering the tongue with the hindermost fibers of the Hyoglossus.
The Styloglossus, the shortest and smallest of the three styloid muscles, arises from the anterior and lateral surfaces of the
styloid process, near its apex, and from the stylomandibular ligament. Passing downward and forward between the internal
and external carotid arteries, it divides upon the side of the tongue near its dorsal surface, blending with the fibers of the
Longitudinalis inferior in front of the Hyoglossus; the other, oblique, overlaps the Hyoglossus and decussates with its fibers.
The intrinsic muscles are: Longitudinalis superior. Transversus. Longitudinalis inferior. Verticalis.
The Longitudinalis linguae superior (Superior lingualis) is a thin stratum of oblique and longitudinal fibers immediately
underlying the mucous membrane on the dorsum of the tongue. It arises from the submucous fibrous layer close to the epiglottis and from the median fibrous septum, and runs forward to the edges of the tongue.
The Longitudinalis linguae inferior (Inferior lingualis) is a narrow band situated on the under surface of the tongue between the Genioglossus and Hyoglossus. It extends from the root to the apex of the tongue: behind, some of its fibers are
connected with the body of the hyoid bone; in front it blends with the fibers of the Styloglossus.
The Transversus linguae (Transverse lingualis) consists of fibers which arise from the median fibrous septum and pass
lateralward to be inserted into the submucous fibrous tissue at the sides of the tongue.
The Verticalis linguae (Vertical lingualis) is found only at the borders of the forepart of the tongue. Its fibers extend from
the upper to the under surface of the organ.
The median fibrous septum of the tongue is very complete, so that the anastomosis between the two lingual arteries is not
very free.
Actions. The movements of the tongue, although numerous and complicated, may be understood by carefully considering
the direction of the fibers of its muscles. The Genioglossi, by means of their posterior fibers, draw the root of the tongue
forward, and protrude the apex from the mouth. The anterior fibers draw the tongue back into the mouth. The two muscles
acting in their entirety draw the tongue downward, so as to make its superior surface concave from side to side, forming a
channel along which fluids may pass toward the pharynx, as in sucking. The Hyoglossi depress the tongue, and draw down
its sides. The Styloglossi draw the tongue upward and backward. The Glossopalatini draw the root of the tongue upward.
The intrinsic muscles are mainly concerned in altering the shape of the tongue, whereby it becomes shortened, narrowed, or
curved in different directions; thus, the Longitudinalis superior and inferior tend to shorten the tongue, but the former, in
addition, turn the tip and sides upward so as to render the dorsum concave, while the latter pull the tip downward and render the dorsum convex. The Transversus narrows and elongates the tongue, and the Verticalis flattens and broadens it. The
complex arrangement of the muscular fibers of the tongue, and the various directions in which they run, give to this organ
the power of assuming the forms necessary for the enunciation of the different consonantal sounds; and Macalister states
“there is reason to believe that the musculature of the tongue varies in different races owing to the hereditary practice and
habitual use of certain motions required for enunciating the several vernacular languages.”
Glands of the Tongue. The tongue is provided with mucous and serous glands.
The mucous glands are similar in structure to the labial and buccal glands. They are found especially at the back part behind
the vallate papillae, but are also present at the apex and marginal parts. In this connection the anterior lingual glands (Blan-
din or Nuhn) require special notice. They are situated on the under surface of the apex of the tongue, one on either side of
the frenulum, where they are covered by a fasciculus of muscular fibers derived from the Styloglossus and Longitudinalis
inferior. They are from 12 to 25 mm. long, and about 8 mm. broad, and each opens by three or four ducts on the under surface of the apex.
The serous glands occur only at the back of the tongue in the neighborhood of the taste-buds, their ducts opening for the
most part into the fossae of the vallate papillae. These glands are racemose, the duct of each branching into several minute
ducts, which end in alveoli, lined by a single layer of more or less columnar epithelium. Their secretion is of a watery nature, and probably assists in the distribution of the substance to be tasted over the taste area. (Ebner.)
The Salivary Glands. Three large pairs of salivary glands communicate with the mouth, and pour their secretion into its
cavity; they are the parotid, submaxillary, and sublingual.
Parotid Gland (glandula parotis), the largest of the three, varies in weight from 14 to 28 gm. It lies upon the side of the
face, immediately below and in front of the external ear. The main portion of the gland is superficial, somewhat flattened
and quadrilateral in form, and is placed between the ramus of the mandible in front and the mastoid process and Sternocleidomastoideus behind, overlapping, however, both boundaries. Above, it is broad and reaches nearly to the zygomatic
arch; below, it tapers somewhat to about the level of a line joining the tip of the mastoid process to the angle of the mandible. The remainder of the gland is irregularly wedge-shaped, and extends deeply inward toward the pharyngeal wall.
The gland is enclosed within a capsule continuous with the deep cervical fascia; the layer covering the superficial surface
is dense and closely adherent to the gland; a portion of the fascia, attached to the styloid process and the angle of the mandible, is thickened to form the stylomandibular ligament which intervenes between the parotid and submaxillary glands.
The anterior surface of the gland is moulded on the posterior border of the ramus of the mandible, clothed by the Pterygoideus internus and Masseter. The inner lip of the groove dips, for a short distance, between the two Pterygoid muscles,
while the outer lip extends for some distance over the superficial surface of the Masseter; a small portion of this lip immediately below the zygomatic arch is usually detached, and is named the accessory part (socia parotidis) of the gland.
The posterior surface is grooved longitudinally and abuts against the external acoustic meatus, the mastoid process, and the
anterior border of the Sternocleidomastoideus.
The superficial surface, slightly lobulated, is covered by the integument, the superficial fascia containing the facial branches of the great auricular nerve and some small lymph glands, and the fascia which forms the capsule of the gland.
The deep surface extends inward by means of two processes, one of which lies on the Digastricus, styloid process, and the
styloid group of muscles, and projects under the mastoid process and Sternocleidomastoideus; the other is situated in front
of the styloid process, and sometimes passes into the posterior part of the mandibular fossa behind the temporomandibular
joint. The deep surface is in contact with the internal and external carotid arteries, the internal jugular vein, and the vagus
and glossopharyngeal nerves.
The gland is separated from the pharyngeal wall by some loose connective tissue.
The parotid duct (ductus parotideus; Stensen’s duct) is about 7 cm. long. It begins by numerous branches from the anterior
part of the gland, crosses the Masseter, and at the anterior border of this muscle turns inward nearly at a right angle, passes
through the corpus adiposum of the cheek and pierces the Buccinator; it then runs for a short distance obliquely forward
between the Buccinator and mucous membrane of the mouth, and opens upon the oral surface of the cheek by a small orifice, opposite the second upper molar tooth. While crossing the Masseter, it receives the duct of the accessory portion; in
this position it lies between the branches of the facial nerve; the accessory part of the gland and the transverse facial artery
are above it.
Submaxillary Gland (glandula submaxillaris) is irregular in form and about the size of a walnut. A considerable part of it is
situated in the submaxillary triangle, reaching forward to the anterior belly of the Digastricus and backward to the stylomandibular ligament, which intervenes between it and the parotid gland. Above, it extends under cover of the body of the
mandible; below, it usually overlaps the intermediate tendon of the Digastricus and the insertion of the Stylohyoideus,
while from its deep surface a tongue-like deep process extends forward above the Mylohyoideus muscle.
Its superficial surface consists of an upper and a lower part. The upper part is directed outward, and lies partly against the
submaxillary depression on the inner surface of the body of the mandible, and partly on the Pterygoideus internus. The
lower part is directed downward and outward, and is covered by the skin, superficial fascia, Platysma, and deep cervical
fascia; it is crossed by the anterior facial vein and by filaments of the facial nerve; in contact with it, near the mandible, are
the submaxillary lymph glands.
The deep surface is in relation with the Mylohyoideus, Hyoglossus, Styloglossus, Stylohyoideus, and posterior belly of the
Digastricus; in contact with it are the mylohyoid nerve and the mylohyoid and submental vessels.
The external maxillary artery is imbedded in a groove in the posterior border of the gland.
The deep process of the gland extends forward between the Mylohyoideus below and externally, and the Hyoglossus and
Styloglossus internally; above it is the lingual nerve and submaxillary ganglion; below it the hypoglossal nerve and its accompanying vein.
The submaxillary duct (ductus submaxillaris; Wharton’s duct) is about 5 cm. long, and its wall is much thinner than that of
the parotid duct. It begins by numerous branches from the deep surface of the gland, and runs forward between the Mylohyoideus and the Hyoglossus and Genioglossus, then between the sublingual gland and the Genioglossus, and opens by a
narrow orifice on the summit of a small papilla, at the side of the frenulum linguae. On the Hyoglossus it lies between the
lingual and hypoglossal nerves, but at the anterior border of the muscle it is crossed laterally by the lingual nerve; the terminal branches of the lingual nerve ascend on its medial side.
Sublingual Gland (glandula sublingualis) is the smallest of the three glands. It is situated beneath the mucous membrane of
the floor of the mouth, at the side of the frenulum linguae, in contact with the sublingual depression on the inner surface of
the mandible, close to the symphysis. It is narrow, flattened, shaped somewhat like an almond, and weighs nearly 2 gm. It
is in relation, above, with the mucous membrane; below, with the Mylohyoideus; behind, with the deep part of the submaxillary gland; laterally, with the mandible; and medially, with the Genioglossus, from which it is separated by the lingual
nerve and the submaxillary duct. Its excretory ducts are from eight to twenty in number. Of the smaller sublingual ducts
(ducts of Rivinus), some join the submaxillary duct; others open separately into the mouth, on the elevated crest of mucous
membrane (plica sublingualis), caused by the projection of the gland, on either side of the frenulum linguae. One or more
join to form the larger sublingual duct (duct of Bartholin), which opens into the submaxillary duct.
Accessory Glands. Besides the salivary glands proper, numerous other glands are found in the mouth. Many of these glands
are found at the posterior part of the dorsum of the tongue behind the vallate papillae, and also along its margins as far forward as the apex. Others lie around and in the palatine tonsil between its crypts, and large numbers are present in the soft
palate, the lips, and cheeks. These glands are of the same structure as the larger salivary glands, and are of the mucous or
mixed type.
The Fauces. The aperture by which the mouth communicates with the pharynx is called the isthmus faucium. It is bounded,
above, by the soft palate; below, by the dorsum of the tongue; and on either side, by the glossopalatine arch.
The glossopalatine arch (arcus glossopalatinus; anterior pillar of fauces) on either side runs downward, lateralward, and
forward to the side of the base of the tongue, and is formed by the projection of the Glossopalatinus with its covering mucous membrane.
The pharyngopalatine arch (arcus pharyngopalatinus; posterior pillar of fauces) is larger and projects farther toward the
middle line than the anterior; it runs downward, lateralward, and backward to the side of the pharynx, and is formed by the
projection of the Pharyngopalatinus, covered by mucous membrane. On either side the two arches are separated below by a
triangular interval, in which the palatine tonsil is lodged.
The Palatine Tonsils (tonsillae palatinae tonsil) are two prominent masses situated one on either side between the glossopalatine and pharyngopalatine arches. Each tonsil consists fundamentally of an aggregation of lymphoid tissue underlying the mucous membrane between the palatine arches. The lymphoid mass, however, does not completely fill the interval
between the two arches, so that a small depression, the supratonsillar fossa, exists at the upper part of the interval. Further,
the tonsil extends for a variable distance under cover of the glossopalatine arch, and is here covered by a reduplication of
mucous membrane; the upper part of this fold reaches across the supratonsillar fossa, between the two arches, as a thin fold
sometimes termed the plica semilunaris; the remainder of the fold is called the plica triangularis. Between the plica triangularis and the surface of the tonsil is a space known as the tonsillar sinus; in many cases, however, this sinus is obliterated by
its walls becoming adherent. From this description it will be apparent that a portion of the tonsil is below the level of the
surrounding mucous membrane, i. e., is imbedded, while the remainder projects as the visible tonsil. In the child the tonsils
are relatively (and frequently absolutely) larger than in the adult, and about one-third of the tonsil is imbedded. After puberty the imbedded portion diminishes considerably in size and the tonsil assumes a disk-like form, flattened from side to side;
the shape; and size of the tonsil, however, vary considerably in different individuals.
The medial surface of the tonsil is free except anteriorly, where it is covered by the plica triangularis; it presents from
twelve to fifteen orifices leading into small crypts or recesses from which numerous follicles branch out into the tonsillar
substance.
The lateral or deep surface is adherent to a fibrous capsule which is continued into the plica triangularis. It is separated
from the inner surface of the Constrictor pharyngis superior usually by some loose connective tissue; this muscle intervenes
between the tonsil and the external maxillary artery with its tonsillar and ascending palatine branches. The internal carotid
artery lies behind and lateral to the tonsil at a distance of 20 to 25 mm. from it.
The tonsils form part of a circular band of adenoid tissue which guards the opening into the digestive and respiratory tubes.
The anterior part of the ring is formed by the submucous adenoid collections (lingual tonsil) on the posterior part of the
tongue; the lateral portions consist of the palatine tonsils and the adenoid collections in the vicinity of the auditory tubes,
while the ring is completed behind by the pharyngeal tonsil on the posterior wall of the pharynx. In the intervals between
these main masses are smaller collections of adenoid tissue.
Palatine Aponeurosis. Attached to the posterior border of the hard palate is a thin, firm fibrous lamella which supports the
muscles and gives strength to the soft palate. It is thicker above than below, where it becomes very thin and difficult to define. Laterally it is continuous with the pharyngeal aponeurosis.
The muscles of the palate are: Levator veli palatini. Glossopalatinus. Tensor veli palatini. Pharyngopalatinus. Musculus
uvulae.
The Levator veli palatini (Levator palati) is a thick, rounded muscle situated lateral to the choanae. It arises from the under
surface of the apex of the petrous part of the temporal bone and from the medial lamina of the cartilage of the auditory tube.
After passing above the upper concave margin of the Constrictor pharyngis superior it spreads out in the palatine velum, its
fibers extending obliquely downward and medialward to the middle line, where they blend with those of the opposite side.
The Tensor veli palatini (Tensor palati) is a broad, thin, ribbon-like muscle placed lateral to the Levator veli palatini. It
arises by a flat lamella from the scaphoid fossa at the base of the medial pterygoid plate, from the spina angularis of the
sphenoid and from the lateral wall of the cartilage of the auditory tube. Descending vertically between the medial pterygoid
plate and the Pterygoideus internus it ends in a tendon which winds around the pterygoid hamulus, being retained in this
situation by some of the fibers of origin of the Pterygoideus internus. Between the tendon and the hamulus is a small bursa.
The tendon then passes medialward and is inserted into the palatine aponeurosis and into the surface behind the transverse
ridge on the horizontal part of the palatine bone.
The Musculus uvulae (Azygos uvulae) arises from the posterior nasal spine of the palatine bones and from the palatine aponeurosis; it descends to be inserted into the uvula.
The Glossopalatinus (Palatoglossus) is a small fleshy fasciculus, narrower in the middle than at either end, forming, with
the mucous membrane covering its surface, the glossopalatine arch. It arises from the anterior surface of the soft palate,
where it is continuous with the muscle of the opposite side, and passing downward, forward, and lateralward in front of the
palatine tonsil, is inserted into the side of the tongue, some of its fibers spreading over the dorsum, and others passing deeply into the substance of the organ to intermingle with the Transversus linguae.
The Pharyngopalatinus (Palatopharyngeus) is a long, fleshy fasciculus narrower in the middle than at either end, forming,
with the mucous membrane covering its surface, the pharyngopalatine arch. It is separated from the Glossopalatinus by an
angular interval, in which the palatine tonsil is lodged. It arises from the soft palate, where it is divided into two fasciculi by
the Levator veli palatini and Musculus uvulae. The posterior fasciculus lies in contact with the mucous membrane, and
joins with that of the opposite muscle in the middle line; the anterior fasciculus, the thicker, lies in the soft palate between
the Levator and Tensor, and joins in the middle line the corresponding part of the opposite muscle. Passing lateralward and
downward behind the palatine tonsil, the Pharyngopalatinus joins the Stylopharyngeus, and is inserted with that muscle into
the posterior border of the thyroid cartilage, some of its fibers being lost on the side of the pharynx and others passing
across the middle line posteriorly, to decussate with the muscle of the opposite side.
Actions. - During the first stage of deglutition, the bolus of food is driven back into the fauces by the pressure of the tongue
against the hard palate, the base of the tongue being, at the same time, retracted, and the larynx raised with the pharynx.
During the second stage the entrance to the larynx is closed by the drawing forward of the arytenoid cartilages toward the
cushion of the epiglottis - a movement produced by the contraction of the Thyreoarytaenoidei, the Arytaenoidei, and the
Arytaenoepiglottidei.
After leaving the tongue the bolus passes on to the posterior or laryngeal surface of the epiglottis, and glides along this for a
certain distance; then the Glossopalatini, the constrictors of the fauces, contract behind it; the palatine velum is slightly
raised by the Levator veli palatini, and made tense by the Tensor veli palatini; and the Pharyngopalatini, by their contraction, pull the pharynx upward over the bolus, and come nearly together, the uvula filling up the slight interval between
them. By these means the food is prevented from passing into the nasal part of the pharynx; at the same time, the Pharyngopalatini form an inclined plane, directed obliquely downward and backward along the under surface of which the bolus
descends into the lower part of the pharynx. The Salpingopharyngei raise the upper and lateral parts of the pharynx - i. e.,
those parts which are above the points where the Stylopharyngei are attached to the pharynx.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples.
Practice class 2. Anatomy of teeth.
The aim: to learn the general and special features or teeth structure.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, facial surgeons, otorhinolaringologists, stomatologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Teeth (dentes) - Man is provided with two sets of teeth, which make their appearance at different periods of life.
Those of the first set appear in childhood, and are called the deciduous or milk teeth. Those of the second set, which also
appear at an early period, may continue until old age, and are named permanent.
The deciduous teeth are twenty in number: four incisors, two canines, and four molars, in each jaw.
The permanent teeth are thirty-two in number: four incisors, two canines, four premolars, and six molars, in each jaw.
The dental formulae may be represented as follows:
Deciduous Teeth.
mol.
can.
in.
in.
can.
mol.
Upper jaw 2
1
2
2
1
2
Total 20
Lower jaw 2
1
2
2
1
2
Permanent Teeth.
mol.
Upper jaw 3
Lower
3
jaw
pr.mol.
2
2
can.
1
1
in.
2
2
in.
2
2
can.
1
1
pr.mol.
2
2
mol.
3
3
Total 32
General Characteristics. - Each tooth consists of three portions: the crown, projecting above the gum; the root, imbedded
in the alveolus; and the neck, the constricted portion between the crown and root.
The roots of the teeth are firmly implanted in depressions within the alveoli; these depressions are lined with periosteum
which invests the tooth as far as the neck. At the margins of the alveoli, the periosteum is continuous with the fibrous structure of the gums.
In consequence of the curve of the dental arch, terms such as anterior and posterior, as applied to the teeth, are misleading
and confusing. Special terms are therefore used to indicate the different surfaces of a tooth: the surface directed toward the
lips or cheek is known as the labial or buccal surface; that directed toward the tongue is described as the lingual surface;
those surfaces which touch neighboring teeth are termed surfaces of contact. In the case of the incisor and canine teeth the
surfaces of contact are medial and lateral; in the premolar and molar teeth they are anterior and posterior.
The superior dental arch is larger than the inferior, so that in the normal condition the teeth in the maxillae slightly overlap
those of the mandible both in front and at the sides. Since the upper central incisors are wider than the lower, the other teeth
in the upper arch are thrown somewhat distally, and the two sets do not quite correspond to each other when the mouth is
closed: thus the upper canine tooth rests partly on the lower canine and partly on the first premolar, and the cusps of the
upper molar teeth lie behind the corresponding cusps of the lower molar teeth. The two series, however, end at nearly the
same point behind; this is mainly because the molars in the upper arch are the smaller
The Permanent Teeth (dentes permanentes). - The Incisors (dentes incisivi; incisive or cutting teeth) are so named from
their presenting a sharp cutting edge, adapted for biting the food. They are eight in number, and form the four front teeth in
each dental arch.
The crown is directed vertically, and is chisel-shaped, being bevelled at the expense of its lingual surface, so as to present
a sharp horizontal cutting edge, which, before being subjected to attrition, presents three small prominent points separated
by two slight notches. It is convex, smooth, and highly polished on its labial surface; concave on its lingual surface, where,
in the teeth of the upper arch, it is frequently marked by an inverted V-shaped eminence, situated near the gum. This is
known as the basal ridge or cingulum. The neck is constricted. The root is long, single, conical, transversely flattened,
thicker in front than behind, and slightly grooved on either side in the longitudinal direction.
The upper incisors are larger and stronger than the lower, and are directed obliquely downward and forward. The central
ones are larger than the lateral, and their roots are more rounded.
The lower incisors are smaller than the upper: the central ones are smaller than the lateral, and are the smallest of all the
incisors. They are placed vertically and are somewhat bevelled in front, where they have been worn down by contact with
the overlapping edge of the upper teeth. The cingulum is absent.
The Canine Teeth (dentes canini) are four in number, two in the upper, and two in the lower arch, one being placed laterally to each lateral incisor. They are larger and stronger than the incisors, and their roots sink deeply into the bones, and
cause well-marked prominences upon the surface.
The crown is large and conical, very convex on its labial surface, a little hollowed and uneven on its lingual surface, and
tapering to a blunted point or cusp, which projects beyond the level of the other teeth. The root is single, but longer and
thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side.
The upper canine teeth (popularly called eye teeth) are larger and longer than the lower, and usually present a distinct basal ridge.
The lower canine teeth (popularly called stomach teeth) are placed nearer the middle line than the upper, so that their
summits correspond to the intervals between the upper canines and the lateral incisors.
The Premolars or Bicuspid teeth (dentes praemolares) are eight in number, four in each arch. They are situated lateral to
and behind the canine teeth, and are smaller and shorter than they.
The crown is compressed antero-posteriorly, and surmounted by two pyramidal eminences or cusps, a labial and a lingual,
separated by a groove; hence their name bicuspid. Of the two cusps the labial is the larger and more prominent. The neck is
oval. The root is generally single, compressed, and presents in front and behind a deep groove, which indicates a tendency
in the root to become double. The apex is generally bifid.
The upper premolars are larger, and present a greater tendency to the division of their roots than the lower; this is especially the case in the first upper premolar.
The Molar Teeth (dentes molares) are the largest of the permanent set, and their broad crowns are adapted for grinding
and pounding the food. They are twelve in number; six in each arch, three being placed posterior to each of the second
premolars.
The crown of each is nearly cubical in form, convex on its buccal and lingual surfaces, flattened on its surfaces of contact;
it is surmounted by four or five tubercles, or cusps, separated from each other by a crucial depression; hence the molars are
sometimes termed multicuspids. The neck is distinct, large, and rounded.
Upper Molars. - As a rule the first is the largest, and the third the smallest of the upper molars. The crown of the first has
usually four tubercles; that of the second, three or four; that of the third, three. Each upper molar has three roots, and of
these two are buccal and nearly parallel to one another; the third is lingual and diverges from the others as it runs upward.
The roots of the third molar (dens serotinus or wisdom-tooth) are more or less fused together.
Lower Molars. - The lower molars are larger than the upper. On the crown of the first there are usually five tubercles; on
those of the second and third, four or five. Each lower molar has two roots, an anterior, nearly vertical, and a posterior, di-
rected obliquely backward; both roots are grooved longitudinally, indicating a tendency to division. The two roots of the
third molar (dens serotinus or wisdom tooth) are more or less united.
The Deciduous Teeth (dentes decidui; temporary or milk teeth) - The deciduous are smaller than, but, generally speaking,
resemble in form, the teeth which bear the same names in the permanent set. The hinder of the two molars is the largest of
all the deciduous teeth, and is succeeded by the second premolar. The first upper molar has only three cusps - two labial,
one lingual; the second upper molar has four cusps. The first lower molar has four cusps; the second lower molar has five.
The roots of the deciduous molars are smaller and more divergent than those of the permanent molars, but in other respects
bear a strong resemblance to them.
Structure of the Teeth. - On making a vertical section of a tooth, a cavity will be found in the interior of the crown and the
center of each root; it opens by a minute orifice at the extremity of the latter. This is called the pulp cavity, and contains the
dental pulp, a loose connective tissue richly supplied with vessels and nerves, which enter the cavity through the small aperture at the point of each root. Some of the cells of the pulp are arranged as a layer on the wall of the pulp cavity; they are
named the odontoblasts of Waldeyer, and during the development of the tooth, are columnar in shape, but later on, after the
dentin is fully formed, they become flattened and resemble osteoblasts. Each has two fine processes, the outer one passing
into a dental canaliculus, the inner being continuous with the processes of the connective-tissue cells of the pulp matrix.
The solid portion of the tooth consists of (1) the ivory or dentin, which forms the bulk of the tooth; (2) the enamel, which
covers the exposed part of the crown; and (3) a thin layer of bone, the cement or crusta petrosa, which is disposed on the
surface of the root.
The dentin (substantia eburnea; ivory) forms the principal mass of a tooth. It is a modification of osseous tissue, from
which it differs, however, in structure. On microscopic examination it is seen to consist of a number of minute wavy and
branching tubes, the dental canaliculi, imbedded in a dense homogeneous substance, the matrix.
The dental canaliculi (dentinal tubules) are placed parallel with one another, and open at their inner ends into the pulp
cavity. In their course to the periphery they present two or three curves, and are twisted on themselves in a spiral direction.
These canaliculi vary in direction: thus in a tooth of the mandible they are vertical in the upper portion of the crown, becoming oblique and then horizontal in the neck and upper part of the root, while toward the lower part of the root they are
inclined downward. In their course they divide and subdivide dichotomously, and, especially in the root, give off minute
branches, which join together in loops in the matrix, or end blindly. Near the periphery of the dentin, the finer ramifications
of the canaliculi terminate imperceptibly by free ends. The dental canaliculi have definite walls, consisting of an elastic
homogeneous membrane, the dentinal sheath of Neumann, which resists the action of acids; they contain slender cylindrical
prolongations of the odontoblasts, first described by Tomes, and named Tomes’ fibers or dentinal fibers.
The matrix (intertubular dentin) is translucent, and contains the chief part of the earthy matter of the dentin. In it are a
number of fine fibrils, which are continuous with the fibrils of the dental pulp. After the earthy matter has been removed by
steeping a tooth in weak acid, the animal basis remaining may be torn into laminae which run parallel with the pulp cavity,
across the direction of the tubes. A section of dry dentin often displays a series of somewhat parallel lines - the incremental
lines of Salter. These lines are composed of imperfectly calcified dentin arranged in layers. In consequence of the imperfection in the calcifying process, little irregular cavities are left, termed interglobular spaces (Fig. 1008). Normally a series of
these spaces is found toward the outer surface of the dentin, where they form a layer which is sometimes known as the
granular layer. They have received their name from the fact that they are surrounded by minute nodules or globules of dentin. Other curved lines may be seen parallel to the surface. These are the lines of Schreger, and are due to the optical effect
of simultaneous curvature of the dentinal fibers.
Practice skills
Students are supposed to name and identify the mentioned anatomical structures on samples.
Practice class 3. Structure and topography of pharynx and esophagus. Structure and topography
of stomach
The aim: to learn the structure and relations of pharynx, esophagus, stomach.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, gastroenterologists etc
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The pharynx is that part of the digestive tube which is placed behind the nasal cavities, mouth, and larynx. It is a musculomembranous tube, somewhat conical in form, with the base upward, and the apex downward, extending from the under
surface of the skull to the level of the cricoid cartilage in front, and that of the sixth cervical vertebra behind.
The cavity of the pharynx is about 12.5 cm. long, and broader in the transverse than in the antero-posterior diameter. Its
greatest breadth is immediately below the base of the skull, where it projects on either side, behind the pharyngeal ostium
of the auditory tube, as the pharyngeal recess (fossa of Rosenmüller); its narrowest point is at its termination in the esophagus. It is limited, above, by the body of the sphenoid and basilar part of the occipital bone; below, it is continuous with the
esophagus; posteriorly, it is connected by loose areolar tissue with the cervical portion of the vertebral column, and the prevertebral fascia covering the Longus colli and Longus capitis muscles; anteriorly, it is incomplete, and is attached in succession to the medial pterygoid plate, pterygomandibular raphé, mandible, tongue, hyoid bone, and thyroid and cricoid cartilages; laterally, it is connected to the styloid processes and their muscles, and is in contact with the common and internal
carotid arteries, the internal jugular veins, the glossopharyngeal, vagus, and hypoglossal nerves, and the sympathetic trunks,
and above with small parts of the Pterygoidei interni. Seven cavities communicate with it, viz., the two nasal cavities, the
two tympanic cavities, the mouth, the larynx, and the esophagus. The cavity of the pharynx may be subdivided from above
downward into three parts: nasal, oral, and laryngeal.
The Nasal Part of the Pharynx (pars nasalis pharyngis; nasopharynx) lies behind the nose and above the level of the soft
palate: it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent. In front it communicates through the choanae with the nasal cavities. On its lateral wall is the pharyngeal ostium of the auditory tube,
somewhat triangular in shape, and bounded behind by a firm prominence, the torus or cushion, caused by the medial end of
the cartilage of the tube which elevates the mucous membrane. A vertical fold of mucous membrane, the salpingopharyngeal fold, stretches from the lower part of the torus; it contains the Salpingopharyngeus muscle. A second and smaller fold,
the salpingopalatine fold, stretches from the upper part of the torus to the palate. Behind the ostium of the auditory tube is a
deep recess, the pharyngeal recess (fossa of Rosenmüller). On the posterior wall is a prominence, best marked in childhood,
produced by a mass of lymphoid tissue, which is known as the pharyngeal tonsil. Above the pharyngeal tonsil, in the middle line, an irregular flask-shaped depression of the mucous membrane sometimes extends up as far as the basilar process
of the occipital bone; it is known as the pharyngeal bursa.
The Oral Part of the Pharynx (pars oralis pharyngis) reaches from the soft palate to the level of the hyoid bone. It opens
anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two palatine arches, is the
palatine tonsil.
The Laryngeal Part of the Pharynx (pars laryngea pharyngis) reaches from the hyoid bone to the lower border of the cricoid cartilage, where it is continuous with the esophagus. In front it presents the triangular entrance of the larynx, the base
of which is directed forward and is formed by the epiglottis, while its lateral boundaries are constituted by the aryepiglottic
folds. On either side of the laryngeal orifice is a recess, termed the sinus piriformis, which is bounded medially by the aryepiglottic fold, laterally by the thyroid cartilage and hyothyroid membrane.
The muscles of the pharynx are:
Constrictor inferior. Stylopharyngeus. Constrictor medius. Salpingopharyngeus. Constrictor superior. Pharyngopalatinus.
The Constrictor pharyngis inferior (Inferior constrictor), the thickest of the three constrictors, arises from the sides of the
cricoid and thyroid cartilage. From the cricoid cartilage it arises in the interval between the Cricothyreoideus in front, and
the articular facet for the inferior cornu of the thyroid cartilage behind. On the thyroid cartilage it arises from the oblique
line on the side of the lamina, from the surface behind this nearly as far as the posterior border and from the inferior cornu.
From these origins the fibers spread backward and medialward to be inserted with the muscle of the opposite side into the
fibrous raphé in the posterior median line of the pharynx. The inferior fibers are horizontal and continuous with the circular
fibers of the esophagus; the rest ascend, increasing in obliquity, and overlap the Constrictor medius.
The Constrictor pharyngis medius (Middle constrictor) is a fanshaped muscle, smaller than the preceding. It arises from
the whole length of the upper border of the greater cornu of the hyoid bone, from the lesser cornu, and from the stylohyoid
ligament. The fibers diverge from their origin: the lower ones descend beneath the Constrictor inferior, the middle fibers
pass transversely, and the upper fibers ascend and overlap the Constrictor superior. It is inserted into the posterior median
fibrous raphé, blending in the middle line with the muscle of the opposite side.
The Constrictor pharyngis superior (Superior constrictor) is a quadrilateral muscle, thinner and paler than the other two.
It arises from the lower third of the posterior margin of the medial pterygoid plate and its hamulus, from the pterygomandibular raphé, from the alveolar process of the mandible above the posterior end of the mylohyoid line, and by a few fibers
from the side of the tongue. The fibers curve backward to be inserted into the median raphé, being also prolonged by means
of an aponeurosis to the pharyngeal spine on the basilar part of the occipital bone. The superior fibers arch beneath the Levator veli palatini and the auditory tube. The interval between the upper border of the muscle and the base of the skull is
closed by the pharyngeal aponeurosis, and is known as the sinus of Morgagni.
The Stylopharyngeus is a long, slender muscle, cylindrical above, flattened below. It arises from the medial side of the
base of the styloid process, passes downward along the side of the pharynx between the Constrictores superior and medius,
and spreads out beneath the mucous membrane. Some of its fibers are lost in the Constrictor muscles, while others, joining
with the Pharyngopalatinus, are inserted into the posterior border of the thyroid cartilage. The glossopharyngeal nerve runs
on the lateral side of this muscle, and crosses over it to reach the tongue.
The Salpingopharyngeus arises from the inferior part of the auditory tube near its orifice; it passes downward and blends
with the posterior fasciculus of the Pharyngopalatinus.
Actions. - When deglutition is about to be performed, the pharynx is drawn upward and dilated in different directions, to
receive the food propelled into it from the mouth. The Stylopharyngei, which are much farther removed from one another
at their origin than at their insertion, draw the sides of the pharynx upward and lateralward, and so increase its transverse
diameter; its breadth in the antero-posterior direction is increased by the larynx and tongue being carried forward in their
ascent. As soon as the bolus of food is received in the pharynx, the elevator muscles relax, the pharynx descends, and the
Constrictores contract upon the bolus, and convey it downward into the esophagus.
Structure. - The pharynx is composed of three coats: mucous, fibrous, and muscular.
The pharyngeal aponeurosis, or fibrous coat, is situated between the mucous and muscular layers. It is thick above where
the muscular fibers are wanting, and is firmly connected to the basilar portion of the occipital and the petrous portions of
the temporal bones. As it descends it diminishes in thickness, and is gradually lost. It is strengthened posteriorly by a strong
fibrous band, which is attached above to the pharyngeal spine on the under surface of the basilar portion of the occipital
bone, and passes downward, forming a median raphé, which gives attachment to the Constrictores pharyngis.
The mucous coat is continuous with that lining the auditory tubes, the nasal cavities, the mouth, and the larynx. In the nasal part of the pharynx it is covered by columnar ciliated epithelium; in the oral and laryngeal portions the epithelium is
stratified squamous. Beneath the mucous membrane are found racemose mucous glands; they are especially numerous at
the upper part of the pharynx around the orifices of the auditory tubes.
The esophagus or gullet is a muscular canal, about 23 to 25 cm. long, extending from the pharynx to the stomach. It begins
in the neck at the lower border of the cricoid cartilage, opposite the sixth cervical vertebra, descends along the front of the
vertebral column, through the superior and posterior mediastina, passes through the diaphragm, and, entering the abdomen,
ends at the cardiac orifice of the stomach, opposite the eleventh thoracic vertebra. The general direction of the esophagus is
vertical; but it presents two slight curves in its course. At its commencement it is placed in the middle line; but it inclines to
the left side as far as the root of the neck, gradually passes to the middle line again at the level of the fifth thoracic vertebra,
and finally deviates to the left as it passes forward to the esophageal hiatus in the diaphragm. The esophagus also presents
antero-posterior flexures corresponding to the curvatures of the cervical and thoracic portions of the vertebral column. It is
the narrowest part of the digestive tube, and is most contracted at its commencement, and at the point where it passes
through the diaphragm.
Relations. - The cervical portion of the esophagus is in relation, in front, with the trachea; and at the lower part of the neck,
where it projects to the left side, with the thyroid gland; behind, it rests upon the vertebral column and Longus colli muscles; on either side it is in relation with the common carotid artery (especially the left, as it inclines to that side), and parts
of the lobes of the thyroid gland; the recurrent nerves ascend between it and the trachea; to its left side is the thoracic duct.
The thoracic portion of the esophagus is at first situated in the superior mediastinum between the trachea and the vertebral
column, a little to the left of the median line. It then passes behind and to the right of the aortic arch, and descends in the
posterior mediastinum along the right side of the descending aorta, then runs in front and a little to the left of the aorta, and
enters the abdomen through the diaphragm at the level of the tenth thoracic vertebra. Just before it perforates the diaphragm
it presents a distinct dilatation. It is in relation, in front, with the trachea, the left bronchus, the pericardium, and the diaphragm; behind, it rests upon the vertebral column, the Longus colli muscles, the right aortic intercostal arteries, the thoracic duct, and the hemiazygos veins; and below, near the diaphragm, upon the front of the aorta. On its left side, in the superior mediastinum, are the terminal part of the aortic arch, the left subclavian artery, the thoracic duct, and left pleura, while
running upward in the angle between it and the trachea is the left recurrent nerve; below, it is in relation with the descending thoracic aorta. On its right side are the right pleura, and the azygos vein which it overlaps. Below the roots of the lungs
the vagi descend in close contact with it, the right nerve passing down behind, and the left nerve in front of it; the two
nerves uniting to form a plexus around the tube.
In the lower part of the posterior mediastinum the thoracic duct lies to the right side of the esophagus; higher up, it is
placed behind it, and, crossing about the level of the fourth thoracic vertebra, is continued upward on its left side.
The abdominal portion of the esophagus lies in the esophageal groove on the posterior surface of the left lobe of the liver.
It measures about 1.25 cm. in length, and only its front and left aspects are covered by peritoneum. It is somewhat conical
with its base applied to the upper orifice of the stomach, and is known as the antrum cardiacum.
Structure. - The esophagus has four coats: an external or fibrous, a muscular, a submucous, and an internal or mucous coat.
The muscular coat (tunica muscularis) is composed of two planes of considerable thickness: an external of longitudinal
and an internal of circular fibers. The longitudinal fibers are arranged, at the commencement of the tube, in three fasciculi:
one in front, which is attached to the vertical ridge on the posterior surface of the lamina of the cricoid cartilage; and one at
either side, which is continuous with the muscular fibers of the pharynx: as they descend they blend together, and form a
uniform layer, which covers the outer surface of the tube.8
Accessory slips of muscular fibers pass between the esophagus and the left pleura, where the latter covers the thoracic
aorta, or the root of the left bronchus, or the back of the pericardium.
The circular fibers are continuous above with the Constrictor pharyngis inferior; their direction is transverse at the upper
and lower parts of the tube, but oblique in the intermediate part.
The muscular fibers in the upper part of the esophagus are of a red color, and consist chiefly of the striped variety; but
below they consist for the most part of involuntary fibers.
The submucous coat (tela submucosa) connects loosely the mucous and muscular coats. It contains bloodvessels, nerves,
and mucous glands.
The mucous coat (tunica mucosa) is thick, of a reddish color above, and pale below. It is disposed in longitudinal folds,
which disappear on distension of the tube. Its surface is studded with minute papillae, and it is covered throughout with a
thick layer of stratified squamous epithelium. Beneath the mucous membrane, between it and the areolar coat, is a layer of
longitudinally arranged non-striped muscular fibers. This is the muscularis mucosae. At the commencement of the esophagus it is absent, or only represented by a few scattered bundles; lower down it forms a considerable stratum.
The esophageal glands (glandulae aesophageae) are small compound racemose glands of the mucous type: they are
lodged in the submucous tissue, and each opens upon the surface by a long excretory duct.
The stomach is the most dilated part of the digestive tube, and is situated between the end of the esophagus and the beginning of the small intestine. It lies in the epigastric, umbilical, and left hypochondriac regions of the abdomen, and occupies
a recess bounded by the upper abdominal viscera, and completed in front and on the left side by the anterior abdominal wall
and the diaphragm. The shape and position of the stomach are so greatly modified by changes within itself and in the surrounding viscera that no one form can be described as typical. The chief modifications are determined by (1) the amount of
the stomach contents, (2) the stage which the digestive process has reached, (3) the degree of development of the gastric
musculature, and (4) the condition of the adjacent intestines. It is, however, possible by comparing a series of stomachs to
determine certain markings more or less common to all.
The stomach presents two openings, two borders or curvatures, and two surfaces.
Openings. - The opening by which the esophagus communicates with the stomach is known as the cardiac orifice, and is
situated on the left of the middle line at the level of the tenth thoracic vertebra. The short abdominal portion of the esophagus (antrum cardiacum) is conical in shape and curved sharply to the left, the base of the cone being continuous with the
cardiac orifice of the stomach. The right margin of the esophagus is continuous with the lesser curvature of the stomach,
while the left margin joins the greater curvature at an acute angle, termed the incisura cardiaca.
The pyloric orifice communicates with the duodenum, and its position is usually indicated on the surface of the stomach
by a circular groove, the duodenopyloric constriction. This orifice lies to the right of the middle line at the level of the upper border of the first lumbar vertebra.
Curvatures. - The lesser curvature (curvatura ventriculi minor), extending between the cardiac and pyloric orifices, forms
the right or posterior border of the stomach. It descends as a continuation of the right margin of the esophagus in front of
the fibers of the right crus of the diaphragm, and then, turning to the right, it crosses the first lumbar vertebra and ends at
the pylorus. Nearer its pyloric than its cardiac end is a well-marked notch, the incisura angularis, which varies somewhat in
position with the state of distension of the viscus; it serves to separate the stomach into a right and a left portion. The lesser
curvature gives attachment to the two layers of the hepatogastric ligament, and between these two layers are the left gastric
artery and the right gastric branch of the hepatic artery.
The greater curvature (curvatura ventriculi major) is directed mainly forward, and is four or five times as long as the lesser curvature. Starting from the cardiac orifice at the incisura cardiaca, it forms an arch backward, upward, and to the left;
the highest point of the convexity is on a level with the sixth left costal cartilage. From this level it may be followed downward and forward, with a slight convexity to the left as low as the cartilage of the ninth rib; it then turns to the right, to the
end of the pylorus. Directly opposite the incisura angularis of the lesser curvature the greater curvature presents a dilatation,
which is the left extremity of the pyloric part; this dilatation is limited on the right by a slight groove, the sulcus intermedius, which is about 2.5 cm, from the duodenopyloric constriction. The portion between the sulcus intermedius and the duodenopyloric constriction is termed the pyloric antrum. At its commencement the greater curvature is covered by peritoneum
continuous with that covering the front of the organ. The left part of the curvature gives attachment to the gastrolienal ligament, while to its anterior portion are attached the two layers of the greater omentum, separated from each other by the
gastroepiploic vessels.
Surfaces. - When the stomach is in the contracted condition, its surfaces are directed upward and downward respectively,
but when the viscus is distended they are directed forward, and backward. They may therefore be described as anterosuperior and postero-inferior.
Antero-superior Surface. - The left half of this surface is in contact with the diaphragm, which separates it from the base of
the left lung, the pericardium, and the seventh, eighth, and ninth ribs, and intercostal spaces of the left side. The right half is
in relation with the left and quadrate lobes of the liver and with the anterior abdominal wall. When the stomach is empty,
the transverse colon may lie on the front part of this surface. The whole surface is covered by peritoneum.
The Postero-inferior Surface is in relation with the diaphragm, the spleen, the left suprarenal gland, the upper part of the
front of the left kidney, the anterior surface of the pancreas, the left colic flexure, and the upper layer of the transverse mesocolon. These structures form a shallow bed, the stomach bed, on which the viscus rests. The transverse mesocolon separates the stomach from the duodenojejunal flexure and small intestine. The postero-inferior surface is covered by peritoneum, except over a small area close to the cardiac orifice; this area is limited by the lines of attachment of the gastrophrenic
ligament, and lies in apposition with the diaphragm, and frequently with the upper portion of the left suprarenal gland.
Component Parts of the Stomach. - A plane passing through the incisura angularis on the lesser curvature and the left limit
of the opposed dilatation on the greater curvature divides the stomach into a left portion or body and a right or pyloric portion. The left portion of the body is known as the fundus, and is marked off from the remainder of the body by a plane passing horizontally through the cardiac orifice. The pyloric portion is divided by a plane through the sulcus intermedius at
right angles to the long axis of this portion; the part to the right of this plane is the pyloric antrum
If the stomach be examined during the process of digestion it will be found divided by a muscular constriction into a large
dilated left portion, and a narrow contracted tubular right portion. The constriction is in the body of the stomach, and does
not follow any of the anatomical landmarks; indeed, it shifts gradually toward the left as digestion progresses, i. e., more of
the body is gradually absorbed into the tubular part
Position of the Stomach. - The position of the stomach varies with the posture, with the amount of the stomach contents
and with the condition of the intestines on which it rests. In the erect posture the empty stomach is somewhat J-shaped; the
part above the cardiac orifice is usually distended with gas; the pylorus descends to the level of the second lumbar vertebra
and the most dependent part of the stomach is at the level of the umbilicus. Variation in the amount of its contents affects
mainly the cardiac portion, the pyloric portion remaining in a more or less contracted condition during the process of digestion. As the stomach fills it tends to expand forward and downward in the direction of least resistance, but when this is in-
terfered with by a distended condition of the colon or intestines the fundus presses upward on the liver and diaphragm and
gives rise to the feelings of oppression and palpitation complained of in such cases.
The position of the full stomach depends, as already indicated, on the state of the intestines; when these are empty the
fundus expands vertically and also forward, the pylorus is displaced toward the right and the whole organ assumes an
oblique position, so that its surfaces are directed more forward and backward. The lowest part of the stomach is at the pyloric vestibule, which reaches to the region of the umbilicus. Where the intestines interfere with the downward expansion of
the fundus the stomach retains the horizontal position which is characteristic of the contracted viscus.
Examination of the stomach during life by x-rays has confirmed these findings, and has demonstrated that, in the erect
posture, the full stomach usually presents a hook-like appearance, the long axis of the clinical fundus being directed downward, medialward, and forward toward the umbilicus, while the pyloric portion curves upward to the duodenopyloric junction.
Interior of the Stomach. - When examined after death, the stomach is usually fixed at some temporary stage of the digestive process. If the viscus be laid open by a section through the plane of its two curvatures, it is seen to consist of two segments: (a) a large globular portion on the left and (b) a narrow tubular part on the right. These correspond to the clinical
subdivisions of fundus and pyloric portions already described, and are separated by a constriction which indents the body
and greater curvature, but does not involve the lesser curvature. To the left of the cardiac orifice is the incisura cardiaca: the
projection of this notch into the cavity of the stomach increases as the organ distends, and has been supposed to act as a
valve preventing regurgitation into the esophagus. In the pyloric portion are seen: (a) the elevation corresponding to the
incisura angularis, and (b) the circular projection from the duodenopyloric constriction which forms the pyloric valve; the
separation of the pyloric antrum from the rest of the pyloric part is scarcely indicated.
The pyloric valve (valvula pylori) is formed by a reduplication of the mucous membrane of the stomach, covering a muscular ring composed of a thickened portion of the circular layer of the muscular coat. Some of the deeper longitudinal fibers
turn in and interlace with the circular fibers of the valve.
Structure. - The wall of the stomach consists of four coats: serous, muscular, submucous, and mucous, together with vessels and nerves.
The serous coat (tunica serosa) is derived from the peritoneum, and covers the entire surface of the organ, excepting along
the greater and lesser curvatures at the points of attachment of the greater and lesser omenta; here the two layers of peritoneum leave a small triangular space, along which the nutrient vessels and nerves pass. On the posterior surface of the stomach, close to the cardiac orifice, there is also a small area uncovered by peritoneum, where the organ is in contact with the
under surface of the diaphragm.
The muscular coat (tunica muscularis) is situated immediately beneath the serous covering, with which it is closely connected. It consists of three sets of smooth muscle fibers: longitudinal, circular and oblique.
The longitudinal fibers (stratum longitudinale) are the most superficial, and are arranged in two sets. The first set consists
of fibers continuous with the longitudinal fibers of the esophagus; they radiate in a stellate manner from the cardiac orifice
and are practically all lost before the pyloric portion is reached. The second set commences on the body of the stomach and
passes to the right, its fibers becoming more thickly distributed as they approach the pylorus. Some of the more superficial
fibers of this set pass on to the duodenum, but the deeper fibers dip inward and interlace with the circular fibers of the pyloric valve.
The circular fibers (stratum circulare) form a uniform layer over the whole extent of the stomach beneath the longitudinal
fibers. At the pylorus they are most abundant, and are aggregated into a circular ring, which projects into the lumen, and
forms, with the fold of mucous membrane covering its surface, the pyloric valve. They are continuous with the circular
fibers of the esophagus, but are sharply marked off from the circular fibers of the duodenum.
The oblique fibers (fibrae obliquae) internal to the circular layer, are limited chiefly to the cardiac end of the stomach,
where they are disposed as a thick uniform layer, covering both surfaces, some passing obliquely from left to right, others
from right to left, around the cardiac end.
The submucous coat (tela submucosa) consists of a loose, areolar tissue, connecting the mucous and muscular layers.
The mucous membrane (tunica mucosa) is thick and its surface is smooth, soft, and velvety. In the fresh state it is of a
pinkish tinge at the pyloric end, and of a red or reddish-brown color over the rest of its surface. In infancy it is of a brighter
hue, the vascular redness being more marked. It is thin at the cardiac extremity, but thicker toward the pylorus. During the
contracted state of the organ it is thrown into numerous plaits or rugae, which, for the most part, have a longitudinal direction, and are most marked toward the pyloric end of the stomach, and along the greater curvature. These folds are entirely
obliterated when the organ becomes distended.
Structure of the Mucous Membrane. - When examined with a lens, the inner surface of the mucous membrane presents a
peculiar honeycomb appearance from being covered with small shallow depressions or alveoli, of a polygonal or hexagonal
form, which vary from 0.12 to 0.25 mm. in diameter. These are the ducts of the gastric glands, and at the bottom of each
may be seen one or more minute orifices, the openings of the gland tubes. The surface of the mucous membrane is covered
by a single layer of columnar epithelium with occasional goblet cells. This epithelium commences very abruptly at the cardiac orifice, where there is a sudden transition from the stratified epithelium of the esophagus. The epithelial lining of the
gland ducts is of the same character and is continuous with the general epithelial lining of the stomach
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples.
Practice class 4. Structure and topography of small intestine and large intestine.
The aim: to learn the anatomy and relations of small and large intestine.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, gastroenterologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The small intestine is a convoluted tube, extending from the pylorus to the colic valve, where it ends in the large intestine.
It is about 7 meters long, and gradually diminishes in size from its commencement to its termination. It is contained in the
central and lower part of the abdominal cavity, and is surrounded above and at the sides by the large intestine; a portion of
it extends below the superior aperture of the pelvis and lies in front of the rectum. It is in relation, in front, with the greater
omentum and abdominal parietes, and is connected to the vertebral column by a fold of peritoneum, the mesentery. The
small intestine is divisible into three portions: the duodenum, the jejunum, and the ileum.
The Duodenum has received its name from being about equal in length to the breadth of twelve fingers (25 cm.). It is the
shortest, the widest, and the most fixed part of the small intestine, and has no mesentery, being only partially covered by
peritoneum. Its course presents a remarkable curve, somewhat of the shape of an imperfect circle, so that its termination is
not far removed from its starting-point.
In the adult the course of the duodenum is as follows: commencing at the pylorus it passes backward, upward, and to the
right, beneath the quadrate lobe of the liver to the neck of the gall-bladder, varying slightly in direction according to the
degree of distension of the stomach: it then takes a sharp curve and descends along the right margin of the head of the pancreas, for a variable distance, generally to the level of the upper border of the body of the fourth lumbar vertebra. It now
takes a second bend, and passes from right to left across the vertebral column, having a slight inclination upward; and on
the left side of the vertebral column it ascends for about 2.5 cm., and then ends opposite the second lumbar vertebra in the
jejunum. As it unites with the jejunum it turns abruptly forward, forming the duodendojejunal flexure. From the above description it will be seen that the duodenum may be divided into four portions: superior, descending, horizontal, and ascending.
Relations. - The superior portion (pars superior; first portion) is about 5 cm. long. Beginning at the pylorus, it ends at the
neck of the gall-bladder. It is the most movable of the four portions. It is almost completely covered by peritoneum, but a
small part of its posterior surface near the neck of the gall-bladder and the inferior vena cava is uncovered; the upper border
of its first half has the hepatoduodenal ligament attached to it, while to the lower border of the same segment the greater
omentum is connected. It is in such close relation with the gall-bladder that it is usually found to be stained by bile after
death, especially on its anterior surface. It is in relation above and in front with the quadrate lobe of the liver and the gallbladder; behind with the gastroduodenal artery, the common bile duct, and the portal vein; and below and behind with the
head and neck of the pancreas.
The descending portion (pars descendens; second portion) is from 7 to 10 cm. long, and extends from the neck of the gallbladder, on a level with the first lumbar vertebra, along the right side of the vertebral column as low as the upper border of
the body of the fourth lumbar vertebra. It is crossed in its middle third by the transverse colon, the posterior surface of
which is uncovered by peritoneum and is connected to the duodenum by a small quantity of connective tissue. The supraand infracolic portions are covered in front by peritoneum, the infracolic part by the right leaf of the mesentery. Posteriorly
the descending portion of the duodenum is not covered by peritoneum. The descending portion is in relation, in front, from
above downward, with the duodenal impression on the right lobe of the liver, the transverse colon, and the small intestine;
behind, it has a variable relation to the front of the right kidney in the neighborhood of the hilum, and is connected to it by
loose areolar tissue; the renal vessels, the inferior vena cava, and the Psoas below, are also behind it. At its medial side is
the head of the pancreas, and the common bile duct; to its lateral side is the right colic flexure. The common bile duct and
the pancreatic duct together perforate the medial side of this portion of the intestine obliquely, some 7 to 10 cm. below the
pylorus; the accessory pancreatic duct sometimes pierces it about 2 cm. above and slightly in front of these.
The horizontal portion (pars horizontalis; third or preaortic or transverse portion) is from 5 to 7.5 cm. long. It begins at the
right side of the upper border of the fourth lumbar vertebra and passes from right to left, with a slight inclination upward, in
front of the great vessels and crura of the diaphragm, and ends in the ascending portion in front of the abdominal aorta. It is
crossed by the superior mesenteric vessels and the mesentery. Its front surface is covered by peritoneum, except near the
middle line, where it is crossed by the superior mesenteric vessels. Its posterior surface is uncovered by peritoneum, except
toward its left extremity, where the posterior layer of the mesentery may sometimes be found covering it to a variable extent. This surface rests upon the right crus of the diaphragm, the inferior vena cava, and the aorta. The upper surface is in
relation with the head of the pancreas.
The ascending portion (pars ascendens; fourth portion) of the duodenum is about 2.5 cm long. It ascends on the left side
of the aorta, as far as the level of the upper border of the second lumbar vertebra, where it turns abruptly forward to become
the jejunum, forming the duodenojejunal flexure. It lies in front of the left Psoas major and left renal vessels, and is covered
in front, and partly at the sides, by peritoneum continuous with the left portion of the mesentery.
The superior part of the duodenum, as stated above, is somewhat movable, but the rest is practically fixed, and is bound
down to neighboring viscera and the posterior abdominal wall by the peritoneum. In addition to this, the ascending part of
the duodenum and the duodenojejunal flexure are fixed by a structure to which the name of Musculus suspensorius duodeni
has been given. This structure commences in the connective tissue around the celiac artery and left crus of the diaphragm,
and passes downward to be inserted into the superior border of the duodenojejunal curve and a part of the ascending duodenum, and from this it is continued into the mesentery. It possesses, according to Treitz, plain muscular fibers mixed with
the fibrous tissue of which it is principally made up. It is of little importance as a muscle, but acts as a suspensory ligament.
Jejunum and Ileum. The remainder of the small intestine from the end of the duodenum is named jejunum and ileum; the
former term being given to the upper two-fifths and the latter to the lower three-fifths. There is no morphological line of
distinction between the two, and the division is arbitrary; but at the same time the character of the intestine gradually undergoes a change from the commencement of the jejunum to the end of the ileum, so that a portion of the bowel taken from
these two situations would present characteristic and marked differences. These are briefly as follows:
The Jejunum (intestinum jejunum) is wider, its diameter being about 4 cm., and is thicker, more vascular, and of a deeper
color than the ileum, so that a given length weighs more. The circular folds (valvulae conniventes) of its mucous membrane
are large and thickly set, and its villi are larger than in the ileum. The aggregated lymph nodules are almost absent in the
upper part of the jejunum, and in the lower part are less frequently found than in the ileum, and are smaller and tend to assume a circular form. By grasping the jejunum between the finger and thumb the circular folds can be felt through the walls
of the gut; these being absent in the lower part of the ileum, it is possible in this way to distinguish the upper from the lower
part of the small intestine.
The Ileum (intestinum ileum) is narrow, its diameter being 3.75 cm., and its coats thinner and less vascular than those of
the jejunum. It possesses but few circular folds, and they are small and disappear entirely toward its lower end, but aggregated lymph nodules (Peyer’s patches) are larger and more numerous. The jejunum for the most part occupies the umbilical
and left iliac regions, while the ileum occupies chiefly the umbilical, hypogastric, right iliac, and pelvic regions. The terminal part of the ileum usually lies in the pelvis, from which it ascends over the right Psoas and right iliac vessels; it ends in
the right iliac fossa by opening into the medial side of the commencement of the large intestine. The jejunum and ileum are
attached to the posterior abdominal wall by an extensive fold of peritoneum, the mesentery, which allows the freest motion,
so that each coil can accommodate itself to changes in form and position. The mesentery is fan-shaped; its posterior border
or root, about 15 cm. long, is attached to the posterior abdominal wall from the left side of the body of the second lumbar
vertebra to the right sacroiliac articulation, crossing successively the horizontal part of the duodenum, the aorta, the inferior
vena cava, the ureter, and right Psoas muscle. Its breadth between its vertebral and intestinal borders averages about 20 cm.,
and is greater in the middle than at its upper and lower ends. the two layers of which it is composed are contained
bloodvessels, nerves, lacteals, and lymph glands, together with a variable amount of fat.
Meckel’s Diverticulum (diverticulum ilei). - This consists of a pouch which projects from the lower part of the ileum in
about 2 per cent. of subjects. Its average position is about 1 meter above the colic valve, and its average length about 5 cm.
Its caliber is generally similar to that of the ileum, and its blind extremity may be free or may be connected with the abdominal wall or with some other portion of the intestine by a fibrous band. It represents the remains of the proximal part of
the vitelline duct, the duct of communication between the yolk-sac and the primitive digestive tube in early fetal life.
Structure. - The wall of the small intestine is composed of four coats: serous, muscular, submuscular, and mucous.
The serous coat (tunica serosa) is derived from the peritoneum. The superior portion of the duodenum is almost completely surrounded by this membrane near its pyloric end, but is only covered in front at the other extremity; the descending
portion is covered by it in front, except where it is carried off by the transverse colon; and the inferior portion lies behind
the peritoneum which passes over it without being closely incorporated with the other coats of this part of the intestine, and
is separated from it in and near the middle line by the superior mesenteric vessels. The rest of the small intestine is surrounded by the peritoneum, excepting along its attached or mesenteric border; here a space is left for the vessels and nerves
to pass to the gut.
The muscular coat (tunica muscularis) consists of two layers of unstriped fibers: an external, longitudinal, and an internal,
circular layer. The longitudinal fibers are thinly scattered over the surface of the intestine, and are more distinct along its
free border. The circular fibers form a thick, uniform layer, and are composed of plain muscle cells of considerable length.
The muscular coat is thicker at the upper than at the lower part of the small intestine.
The submucous coat (tela submucosa) connects together the mucous and muscular layers. It consists of loose, filamentous
areolar tissue containing bloodvessels, lymphatics, and nerves. It is the strongest layer of the intestine.
The mucous membrane (tunica mucosa) is thick and highly vascular at the upper part of the small intestine, but somewhat
paler and thinner below. It consists of the following structures: next the areolar or submucous coat is a double layer of unstriped muscular fibers, outer longitudinal and inner circular, the muscularis mucosae internal to this is a quantity of retiform tissue, enclosing in its meshes lymph corpuscles, and in this the bloodvessels and nerves ramify; lastly, a basement
membrane, supporting a single layer of epithelial cells, which throughout the intestine are columnar in character. The cells
are granular in appearance, and each possesses a clear oval nucleus. At their superficial or unattached ends they present a
distinct layer of highly refracting material, marked by vertical striae, the striated border.
The mucous membrane presents for examination the following structures, contained within it or belonging to it:
Circular folds. Duodenal glands. Villi. Solitary lymphatic nodules. Intestinal glands. Aggregated lymphatic nodules.
The circular folds (plicae circulares [Kerkringi]; valvulae conniventes; valves of Kerkring) are large valvular flaps projecting into the lumen of the bowel. They are composed of reduplications of the mucous membrane, the two layers of the
fold being bound together by submucous tissue; unlike the folds in the stomach, they are permanent, and are not obliterated
when the intestine is distended. The majority extend transversely around the cylinder of the intestine for about one-half or
two-thirds of its circumference, but some form complete circles, and others have a spiral direction; the latter usually extend
a little more than once around the bowel, but occasionally two or three times. The larger folds are about 8 mm. in depth at
their broadest part; but the greater number are of smaller size. The larger and smaller folds alternate with each other. They
are not found at the commencement of the duodenum, but begin to appear about 2.5 or 5 cm. beyond the pylorus. In the
lower part of the descending portion, below the point where the bile and pancreatic ducts enter the intestine, they are very
large and closely approximated. In the horizontal and ascending portions of the duodenum and upper half of the jejunum
they are large and numerous, but from this point, down to the middle of the ileum, they diminish considerably in size. In the
lower part of the ileum they almost entirely disappear; hence the comparative thinness of this portion of the intestine, as
compared with the duodenum and jejunum. The circular folds retard the passage of the food along the intestines, and afford
an increased surface for absorption.
The intestinal villi (villi intestinales) are highly vascular processes, projecting from the mucous membrane of the small
intestine throughout its whole extent, and giving to its surface a velvety appearance. They are largest and most numerous in
the duodenum and jejunum, and become fewer and smaller in the ileum.
Structure of the villi - The essential parts of a villus are: the lacteal vessel, the bloodvessels, the epithelium, the basement
membrane, and the muscular tissue of the mucosa, all being supported and held together by retiform lymphoid tissue.
The lacteals are in some cases double, and in some animals multiple, but usually there is a single vessel. Situated in the
axis of the villus, each commences by dilated cecal extremities near to, but not quite at, the summit of the villus. The walls
are composed of a single layer of endothelial cells.
The muscular fibers are derived from the muscularis mucosae, and are arranged in longitudinal bundless around the lacteal
vessel, extending from the base to the summit of the villus, and giving off, laterally, individual muscle cells, which are enclosed by the reticulum, and by it are attached to the basement-membrane and to the lacteal.
The bloodvessels form a plexus under the basement membrane, and are enclosed in the reticular tissue.
These structures are surrounded by the basement membrane, which is made up of a stratum of endothelial cells, and upon
this is placed a layer of columnar epithelium, the characteristics of which have been described. The retiform tissue forms a
net-work in the meshes of which a number of leucocytes are found.
The intestinal glands (glandulae intestinales [Lieberkühni]; crypts of Lieberkühn) are found in considerable numbers over
every part of the mucous membrane of the small intestine. They consist of minute tubular depressions of the mucous membrane, arranged perpendicularly to the surface, upon which they open by small circular apertures. They may be seen with
the aid of a lens, their orifices appearing as minute dots scattered between the villi. Their walls are thin, consisting of a
basement membrane lined by columnar epithelium, and covered on their exterior by capillary vessels.
The duodenal glands (glandulae duodenales [Brunneri]; Brunner’s glands) are limited to the duodenum, and are found in
the submucous areolar tissue. They are largest and most numerous near the pylorus, forming an almost complete layer in
the superior portion and upper half of the descending portions of the duodenum. They then begin to diminish in number,
and practically disappear at the junction of the duodenum and jejunum. They are small compound acinotubular glands consisting of a number of alveoli lined by short columnar epithelium and opening by a single duct on the inner surface of the
intestine.
The solitary lymphatic nodules (noduli lymphatici solitarii; solitary glands) are found scattered throughout the mucous
membrane of the small intestine, but are most numerous in the lower part of the ileum. Their free surfaces are covered with
rudimentary villi, except at the summits, and each gland is surrounded by the openings of the intestinal glands. Each consists of a dense interlacing retiform tissue closely packed with lymph-corpuscles, and permeated with an abundant capillary
network. The interspaces of the retiform tissue are continuous with larger lymph spaces which surround the gland, through
which they communicate with the lacteal system. They are situated partly in the submucous tissue, partly in the mucous
membrane, where they form slight projections of its epithelial layer.
The aggregated lymphatic nodules (noduli lymphatici aggregati; Peyer’s patches; Peyer’s glands; agminated follicles;
tonsillae intestinales) form circular or oval patches, from twenty to thirty in number, and varying in length from 2 to 10 cm.
They are largest and most numerous in the ileum. In the lower part of the jejunum they are small, circular, and few in number. They are occasionally seen in the duodenum. They are placed lengthwise in the intestine, and are situated in the portion
of the tube most distant from the attachment of the mesentery. Each patch is formed of a group of solitary lymphatic nodules covered with mucous membrane, but the patches do not, as a rule, possess villi on their free surfaces. They are best
marked in the young subject, become indistinct in middle age, and sometimes disappear altogether in advanced life. They
are freely supplied with bloodvessels, which form an abundant plexus around each follicle and give off fine branches permeating the lymphoid tissue in the interior of the follicle. The lymphatic plexuses are especially abundant around these
patches.
The large intestine extends from the end of the ileum to the anus. It is about 1.5 meters long, being one-fifth of the whole
extent of the intestinal canal. Its caliber is largest at its commencement at the cecum, and gradually diminishes as far as the
rectum, where there is a dilatation of considerable size just above the anal canal. It differs from the small intestine in its
greater caliber, its more fixed position, its sacculated form, and in possessing certain appendages to its external coat, the
appendices epiploicae. Further, its longitudinal muscular fibers do not form a continuous layer around the gut, but are arranged in three longitudinal bands or taeniae. The large intestine, in its course, describes an arch which surrounds the convolutions of the small intestine. It commences in the right iliac region, in a dilated part, the cecum. It ascends through the
right lumbar and hypochondriac regions to the under surface of the liver; it here takes a bend, the right colic flexure, to the
left and passes transversely across the abdomen on the confines of the epigastric and umbilical regions, to the left hypochondriac region; it then bends again, the left colic flexure, and descends through the left lumbar and iliac regions to the
pelvis, where it forms a bend called the sigmoid flexure; from this it is continued along the posterior wall of the pelvis to
the anus. The large intestine is divided into the cecum, colon, rectum, and anal canal.
The Cecum (intestinum caecum), the commencement of the large intestine, is the large blind pouch situated below the
colic valve. Its blind end is directed downward, and its open end upward, communicating directly with the colon, of which
this blind pouch appears to be the beginning or head, and hence the old name of caput caecum coli was applied to it. Its size
is variously estimated by different authors, but on an average it may be said to be 6.25 cm. in length and 7.5 in breadth. It is
situated in the right iliac fossa, above the lateral half of the inguinal ligament: it rests on the Iliacus and Psoas major, and
usually lies in contact with the anterior abdominal wall, but the greater omentum and, if the cecum be empty, some coils of
small intestine may lie in front of it. As a rule, it is entirely enveloped by peritoneum, but in a certain number of cases the
peritoneal covering is not complete, so that the upper part of the posterior surface is uncovered and connected to the iliac
fascia by connective tissue. The cecum lies quite free in the abdominal cavity and enjoys a considerable amount of movement, so that it may become herniated down the right inguinal canal, and has occasionally been found in an inguinal hernia
on the left side. The cecum varies in shape, but, according to Treves, in man it may be classified under one of four types. In
early fetal life it is short, conical, and broad at the base, with its apex turned upward and medialward toward the ileocolic
junction. It then resembles the cecum of some monkeys, e. g., mangabey monkey. As the fetus grows the cecum increases
in length more than in breadth, so that it forms a longer tube than in the primitive form and without the broad base, but with
the same inclination of the apex toward the ileocolic junction. This form is seen in other monkeys, e. g., the spider monkey.
As development goes on, the lower part of the tube ceases to grow and the upper part becomes greatly increased, so that at
birth there is a narrow tube, the vermiform process, hanging from a conical projection, the cecum. This is the infantile
form, and as it persists throughout life in about 2 per cent. of cases, it is regarded by Treves as the first of his four types of
human ceca. The cecum is conical and the appendix rises from its apex. The three longitudinal bands start from the appendix and are equidistant from each other. In the second type, the conical cecum has become quadrate by the growing out of a
saccule on either side of the anterior longitudinal band. These saccules are of equal size, and the appendix arises from between them, instead of from the apex of a cone. This type is found in about 3 per cent. of cases. The third type is the normal
type of man. Here the two saccules, which in the second type were uniform, have grown at unequal rates: the right with
greater rapidity than the left. In consequence of this an apparently new apex has been formed by the growing downward of
the right saccule, and the original apex, with the appendix attached, is pushed over to the left toward the ileocolic junction.
The three longitudinal bands still start from the base of the vermiform process, but they are now no longer equidistant from
each other, because the right saccule has grown between the anterior and posterolateral bands, pushing them over to the
left. This type occurs in about 90 per cent. of cases. The fourth type is merely an exaggerated condition of the third; the
right saccule is still larger, and at the same time the left saccule has become atrophied, so that the original apex of the cecum, with the vermiform process, is close to the ileocolic junction, and the anterior band courses medialward to the same
situation. This type is present in about 4 per cent. of cases.
The Vermiform Process or Appendix (processus vermiformis) is a long, narrow, worm-shaped tube, which starts from
what was originally the apex of the cecum, and may pass in one of several directions: upward behind the cecum; to the left
behind the ileum and mesentery; or downward into the lesser pelvis. It varies from 2 to 20 cm. in length, its average being
about 8.3 cm. It is retained in position by a fold of peritoneum (mesenteriole), derived from the left leaf of the mesentery.
This fold, in the majority of cases, is more or less triangular in shape, and as a rule extends along the entire length of the
tube. Between its two layers and close to its free margin lies the appendicular artery. The canal of the vermiform process is
small, extends throughout the whole length of the tube, and communicates with the cecum by an orifice which is placed
below and behind the ileocecal opening. It is sometimes guarded by a semilunar valve formed by a fold of mucous membrane, but this is by no means constant.
Structure. - The coats of the vermiform process are the same as those of the intestine: serous, muscular, submucous, and
mucous. The serous coat forms a complete investment for the tube, except along the narrow line of attachment of its mesenteriole in its proximal two-thirds. The longitudinal muscular fibers do not form three bands as in the greater part of the large
intestine, but invest the whole organ, except at one or two points where both the longitudinal and circular fibers are deficient so that the peritoneal and submucous coats are contiguous over small areas.
The circular muscle fibers form a much thicker layer than the longitudinal fibers, and are separated from them by a small
amount of connective tissue. The submucous coat is well marked, and contains a large number of masses of lymphoid tissue which cause the mucous membrane to bulge into the lumen and so render the latter of small size and irregular shape.
The mucous membrane is lined by columnar epithelium and resembles that of the rest of the large intestine, but the intestinal glands are fewer in number
The Colic Valve (valvula coli; ileocecal valve) - The lower end of the ileum ends by opening into the medial and back part
of the large intestine, at the point of junction of the cecum with the colon. The opening is guarded by a valve, consisting of
two segments or lips, which project into the lumen of the large intestine. If the intestine has been inflated and dried, the lips
are of a semilunar shape. The upper one, nearly horizontal in direction, is attached by its convex border to the line of junction of the ileum with the colon; the lower lip, which is longer and more concave, is attached to the line of junction of the
ileum with the cecum. At the ends of the aperture the two segments of the valve coalesce, and are continued as narrow
membranous ridges around the canal for a short distance, forming the frenula of the valve. The left or anterior end of the
aperture is rounded; the right or posterior is narrow and pointed. In the fresh condition, or in specimens which have been
hardened in situ, the lips project as thick cushion-like folds into the lumen of the large gut, while the opening between them
may present the appearance of a slit or may be somewhat oval in shape.
Each lip of the valve is formed by a reduplication of the mucous membrane and of the circular muscular fibers of the intestine, the longitudinal fibers and peritoneum being continued uninterruptedly from the small to the large intestine.
The surfaces of the valve directed toward the ileum are covered with villi, and present the characteristic structure of the
mucous membrane of the small intestine; while those turned toward the large intestine are destitute of villi, and marked
with the orifices of the numerous tubular glands peculiar to the mucous membrane of the large intestine. These differences
in structure continue as far as the free margins of the valve. It is generally maintained that this valve prevents reflux from
the cecum into the ileum, but in all probability it acts as a sphincter around the end of the ileum and prevents the contents
of the ileum from passing too quickly into the cecum.
The Colon is divided into four parts: the ascending, transverse, descending, and sigmoid.
The Ascending Colon (colon ascendens) is smaller in caliber than the cecum, with which it is continuous. It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on
the right of the gall-bladder, where it is lodged in a shallow depression, the colic impression; here it bends abruptly forward
and to the left, forming the right colic (hepatic) flexure. It is retained in contact with the posterior wall of the abdomen by
the peritoneum, which covers its anterior surface and sides, its posterior surface being connected by loose areolar tissue
with the Iliacus, Quadratus lumborum, aponeurotic origin of Transversus abdominis, and with the front of the lower and
lateral part of the right kidney. Sometimes the peritoneum completely invests it, and forms a distinct but narrow mesocolon.
It is in relation, in front, with the convolutions of the ileum and the abdominal parietes.
The Transverse Colon (colon transversum) the longest and most movable part of the colon, passes with a downward convexity from the right hypochondriac region across the abdomen, opposite the confines of the epigastric and umbilical
zones, into the left hypochondriac region, where it curves sharply on itself beneath the lower end of the spleen, forming the
left colic (splenic) flexure. In its course it describes an arch, the concavity of which is directed backward and a little upward; toward its splenic end there is often an abrupt U-shaped curve which may descend lower than the main curve. It is
almost completely invested by peritoneum, and is connected to the inferior border of the pancreas by a large and wide duplicature of that membrane, the transverse mesocolon. It is in relation, by its upper surface, with the liver and gall-bladder,
the greater curvature of the stomach, and the lower end of the spleen; by its under surface, with the small intestine; by its
anterior surface, with the anterior layers of the greater omentum and the abdominal parietes; its posterior surface is in relation from right to left with the descending portion of the duodenum, the head of the pancreas, and some of the convolutions
of the jejunum and ileum.
The left colic or splenic flexure is situated at the junction of the transverse and descending parts of the colon, and is in
relation with the lower end of the spleen and the tail of the pancreas; the flexure is so acute that the end of the transverse
colon usually lies in contact with the front of the descending colon. It lies at a higher level than, and on a plane posterior to,
the right colic flexure, and is attached to the diaphragm, opposite the tenth and eleventh ribs, by a peritoneal fold, named
the phrenicocolic ligament, which assists in supporting the lower end of the spleen
The Descending Colon (colon descendens) passes downward through the left hypochondriac and lumbar regions along the
lateral border of the left kidney. At the lower end of the kidney it turns medialward toward the lateral border of the Psoas,
and then descends, in the angle between Psoas and Quadratus lumborum, to the crest of the ilium, where it ends in the iliac
colon. The peritoneum covers its anterior surface and sides, while its posterior surface is connected by areolar tissue with
the lower and lateral part of the left kidney, the aponeurotic origin of the Transversus abdominis, and the Quadratus lumborum. It is smaller in caliber and more deeply placed than the ascending colon, and is more frequently covered with peritoneum on its posterior surface than the ascending colon. In front of it are some coils of small intestine.
The Sigmoid Colon (colon sigmoideum; pelvic colon; sigmoid flexure) forms a loop which averages about 40 cm. in
length, and normally lies within the pelvis, but on account of its freedom of movement it is liable to be displaced into the
abdominal cavity. It begins at the superior aperture of the lesser pelvis, where it is continuous with the iliac colon, and
passes transversely across the front of the sacrum to the right side of the pelvis; it then curves on itself and turns toward the
left to reach the middle line at the level of the third piece of the sacrum, where it bends downward and ends in the rectum.
It is completely surrounded by peritoneum, which forms a mesentery (sigmoid mesocolon), which diminishes in length
from the center toward the ends of the loop, where it disappears, so that the loop is fixed at its junctions with the iliac colon
and rectum, but enjoys a considerable range of movement in its central portion. Behind the sigmoid colon are the external
iliac vessels, the left Piriformis, and left sacral plexus of nerves; in front, it is separated from the bladder in the male, and
the uterus in the female, by some coils of the small intestine.
The Rectum (intestinum rectum) is continuous above with the sigmoid colon, while below it ends in the anal canal. From
its origin at the level of the third sacral vertebra it passes downward, lying in the sacrococcygeal curve, and extends for
about 2.5 cm. in front of, and a little below, the tip of the coccyx, as far as the apex of the prostate. It then bends sharply
backward into the anal canal. It therefore presents two antero-posterior curves: an upper, with its convexity backward, and
a lower, with its convexity forward. Two lateral curves are also described, one to the right opposite the junction of the third
and fourth sacral vertebrae, and the other to the left, opposite the left sacrococcygeal articulation; they are, however, of
little importance. The rectum is about 12 cm. long, and at its commencement its caliber is similar to that of the sigmoid
colon, but near its termination it is dilated to form the rectal ampulla. The rectum has no sacculations comparable to those
of the colon, but when the lower part of the rectum is contracted, its mucous membrane is thrown into a number of folds,
which are longitudinal in direction and are effaced by the distension of the gut. Besides these there are certain permanent
transverse folds, of a semilunar shape, known as Houston’s valves. They are usually three in number; sometimes a fourth is
found, and occasionally only two are present. One is situated near the commencement of the rectum, on the right side; a
second extends inward from the left side of the tube, opposite the middle of the sacrum; a third, the largest and most constant, projects backward from the forepart of the rectum, opposite the fundus of the urinary bladder. When a fourth is present, it is situated nearly 2.5 cm. above the anus on the left and posterior wall of the tube. These folds are about 12 mm. in
width, and contain some of the circular fibers of the gut. In the empty state of the intestine they overlap each other, as Houston remarks, so effectually as to require considerable maneuvering to conduct a bougie or the finger along the canal. Their
use seems to be, “to support the weight of fecal matter, and prevent its urging toward the anus, where its presence always
excites a sensation demanding its discharge.
The peritoneum is related to the upper two-thirds of the rectum, covering at first its front and sides, but lower down its
front only; from the latter it is reflected on to the seminal vesicles in the male and the posterior vaginal wall in the female.
The level at which the peritoneum leaves the anterior wall of the rectum to be reflected on to the viscus in front of it is of
considerable importance from a surgical point of view, in connection with the removal of the lower part of the rectum. It is
higher in the male than in the female. In the former the height of the rectovesical excavation is about 7.5 cm., i. e., the
height to which an ordinary index finger can reach from the anus. In the female the height of the rectouterine excavation is
about 5.5 cm. from the anal orifice. The rectum is surrounded by a dense tube of fascia derived from the fascia endopelvina, but fused behind with the fascia covering the sacrum and coccyx. The facial tube is loosely attached to the rectal wall
by areolar tissue in order to allow of distension of the viscus.
Relations of the Rectum. - The upper part of the rectum is in relation, behind, with the superior hemorrhoidal vessels, the
left Piriformis, and left sacral plexus of nerves, which separate it from the pelvic surfaces of the sacral vertebrae; in its lower part it lies directly on the sacrum, coccyx, and Levatores ani, a dense fascia alone intervening; in front, it is separated
above, in the male, from the fundus of the bladder; in the female, from the intestinal surface of the uterus and its appendages, by some convolutions of the small intestine, and frequently by the sigmoid colon; below, it is in relation in the male
with the triangular portion of the fundus of the bladder, the vesiculae seminales, and ductus deferentes, and more anteriorly
with the posterior surface of the prostate; in the female, with the posterior wall of the vagina.
The Anal Canal (pars analis recti), or terminal portion of the large intestine, begins at the level of the apex of the prostate,
is directed downward and backward, and ends at the anus. It forms an angle with the lower part of the rectum, and
measures from 2.5 to 4 cm. in length. It has no peritoneal covering, but is invested by the Sphincter ani internus, supported
by the Levatores ani, and surrounded at its termination by the Sphincter ani externus. In the empty condition it presents the
appearance of an antero-posterior longitudinal slit. Behind it is a mass of muscular and fibrous tissue, the anococcygeal
body; in front of it, in the male, but separated by connective tissue from it, are the membranous portion and bulb of the urethra, and the fascia of the urogenital diaphragm; and in the female it is separated from the lower end of the vagina by a
mass of muscular and fibrous tissue, named the perineal body.
The lumen of the anal canal presents, in its upper half, a number of vertical folds, produced by an infolding of the mucous
membrane and some of the muscular tissue. They are known as the rectal columns [Morgagni], and are separated from one
another by furrows (rectal sinuses), which end below in small valve-like folds, termed anal valves, which join together the
lower ends of the rectal columns.
Structure of the Colon. - The large intestine has four coats: serous, muscular, areolar, and mucous.
The serous coat (tunica serosa) is derived from the peritoneum, and invests the different portions of the large intestine to a
variable extent. The cecum is completely covered by the serous membrane, except in about 5 per cent. of cases where the
upper part of the posterior surface is uncovered. The ascending, descending, and iliac parts of the colon are usually covered
only in front and at the sides; a variable amount of the posterior surface is uncovered. The transverse colon is almost completely invested, the parts corresponding to the attachment of the greater omentum and transverse mesocolon being alone
excepted. The sigmoid colon is entirely surrounded. The rectum is covered above on its anterior surface and sides; below,
on its anterior aspect only; the anal canal is entirely devoid of any serous covering. In the course of the colon the peritoneal
coat is thrown into a number of small pouches filled with fat, called appendices epiploicae. They are most numerous on the
transverse colon.
The muscular coat (tunica muscularis) consists of an external longitudinal, and an internal circular, layer of non-striped
muscular fibers:
The longitudinal fibers do not form a continuous layer over the whole surface of the large intestine. In the cecum and colon they are especially collected into three flat longitudinal bands (taenaei coli), each of about 12 mm. in width; one, the
posterior, is placed along the attached border of the intestine; the anterior, the largest, corresponds along the arch of the
colon to the attachment of the greater omentum, but is in front in the ascending, descending, and iliac parts of the colon,
and in the sigmoid colon; the third, or lateral band, is found on the medial side of the ascending and descending parts of the
colon, and on the under aspect of the transverse colon. These bands are shorter than the other coats of the intestine, and
serve to produce the sacculi which are characteristic of the cecum and colon; accordingly, when they are dissected off, the
tube can be lengthened, and its sacculated character disappears. In the sigmoid colon the longitudinal fibers become more
scattered; and around the rectum they spread out and form a layer, which completely encircles this portion of the gut, but is
thicker on the anterior and posterior surfaces, where it forms two bands, than on the lateral surfaces. In addition, two bands
of plain muscular tissue arise from the second and third coccygeal vertebrae, and pass downward and forward to blend with
the longitudinal muscular fibers on the posterior wall of the anal canal. These are known as the Rectococcygeal muscles.
The circular fibers form a thin layer over the cecum and colon, being especially accumulated in the intervals between the
sacculi; in the rectum they form a thick layer, and in the anal canal they become numerous, and constitute the Sphincter ani
internus.
The submucous coat (tela submucosa) connects the muscular and mucous layers closely together.
The mucous membrane (tunica mucosa) in the cecum and colon, is pale, smooth, destitute of villi, and raised into numerous crescentic folds which correspond to the intervals between the sacculi. In the rectum it is thicker, of a darker color,
more vascular, and connected loosely to the muscular coat, as in the esophagus.
As in the small intestine, the mucous membrane consists of a muscular layer, the muscularis mucosae; a quantity of retiform tissue in which the vessels ramify; a basement membrane and epithelium which is of the columnar variety, and resembles the epithelium found in the small intestine. The mucous membrane of the large intestine presents for examination
glands and solitary lymphatic nodules.
The glands of the great intestine are minute tubular prolongations of the mucous membrane arranged perpendicularly, side
by side, over its entire surface; they are longer, more numerous, and placed in much closer apposition than those of the
small intestine; and they open by minute rounded orifices upon the surface, giving it a cribriform appearance. Each gland is
lined by short columnar epithelium and contains numerous goblet cells.
The solitary lymphatic nodules (noduli lymphatic solitarii) of the large intestine are most abundant in the cecum and vermiform process, but are irregularly scattered also over the rest of the intestine. They are similar to those of the small intestine.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on sample:
Practice class 5. Structure and topography of liver, gallbladder, extrahepatic bile ducts, pancreas, spleen.
The aim: to learn thestructure and relations of liver, gallbladder, extrahepatic bile ducts, pancreas and spleen.
Professional orientation: knowledge on this topic is essential for any medical practitioner, especially therapeutists, gastroenterologists, surgeons.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The liver (hepar), the largest gland in the body, has both external and internal secretions, which are formed in the hepatic
cells. Its external secretion, the bile, is collected after passing through the bile capillaries by the bile ducts, which join like
the twigs and branches of a tree to form two large ducts that unite to form the hepatic duct. The bile is either carried to the
gall-bladder by the cystic duct or poured directly into the duodenum by the common bile duct where it aids in digestion.
The internal secretions are concerned with the metabolism of both nitrogenous and carbohydrate materials absorbed from
the intestine and carried to the liver by the portal vein. The carbohydrates are stored in the hepatic cells in the form of glycogen which is secreted in the form of sugar directly into the blood stream. Some of the cells lining the blood capillaries of
the liver are concerned in the destruction of red blood corpuscles. It is situated in the upper and right parts of the abdominal
cavity, occupying almost the whole of the right hypochondrium, the greater part of the epigastrium, and not uncommonly
extending into the left hypochondrium as far as the mammillary line. In the male it weighs from 1.4 to 1.6 kilogm., in the
female from 1.2 to 1.4 kilogm. It is relatively much larger in the fetus than in the adult, constituting, in the former, about
one-eighteenth, and in the latter about one thirty-sixth of the entire body weight. Its greatest transverse measurement is
from 20 to 22.5 cm. Vertically, near its lateral or right surface, it measures about 15 to 17.5 cm., while its greatest anteroposterior diameter is on a level with the upper end of the right kidney, and is from 10 to 12.5 cm. Opposite the vertebral
column its measurement from before backward is reduced to about 7.5 cm. Its consistence is that of a soft solid; it is friable,
easily lacerated and highly vascular; its color is a dark reddish brown, and its specific gravity is 1.05.
To obtain a correct idea of its shape it must be hardened in situ, and it will then be seen to present the appearance of a
wedge, the base of which is directed to the right and the thin edge toward the left. Symington describes its shape as that “of
a right-angled triangular prism with the right angle rounded off.”
Surfaces. - The liver possesses three surfaces, viz., superior, inferior and posterior. A sharp, well-defined margin divides
the inferior from the superior in front; the other margins are rounded. The superior surface is attached to the diaphragm and
anterior abdominal wall by a triangular or falciform fold of peritoneum, the falciform ligament, in the free margin of which
is a rounded cord, the ligamentum teres (obliterated umbilical vein). The line of attachment of the falciform ligament divides the liver into two parts, termed the right and left lobes, the right being much the larger. The inferior and posterior
surfaces are divided into four lobes by five fossae, which are arranged in the form of the letter H. The left limb of the H
marks on these surfaces the division of the liver into right and left lobes; it is known as the left sagittal fossa, and consists
of two parts, viz., the fossa for the umbilical vein in front and the fossa for the ductus venosus behind. The right limb of the
H is formed in front by the fossa for the gall-bladder, and behind by the fossa for the inferior vena cava; these two fossae
are separated from one another by a band of liver substance, termed the caudate process. The bar connecting the two limbs
of the H is the porta (transverse fissure); in front of it is the quadrate lobe, behind it the caudate lobe.
The superior surface (facies superior) comprises a part of both lobes, and, as a whole, is convex, and fits under the vault
of the diaphragm which in front separates it on the right from the sixth to the tenth ribs and their cartilages, and on the left
from the seventh and eighth costal cartilages. Its middle part lies behind the xiphoid process, and, in the angle between the
diverging rib cartilage of opposite sides, is in contact with the abdominal wall. Behind this the diaphragm separates the
liver from the lower part of the lungs and pleurae, the heart and pericardium and the right costal arches from the seventh to
the eleventh inclusive. It is completely covered by peritoneum except along the line of attachment of the falciform ligament.
The inferior surface (facies inferior; visceral surface), is uneven, concave, directed downward, backward, and to the left,
and is in relation with the stomach and duodenum, the right colic flexure, and the right kidney and suprarenal gland. The
surface is almost completely invested by peritoneum; the only parts devoid of this covering are where the gall-bladder is
attached to the liver, and at the porta hepatis where the two layers of the lesser omentum are separated from each other by
the bloodvessels and ducts of the liver. The inferior surface of the left lobe presents behind and to the left the gastric impression, moulded over the antero-superior surface of the stomach, and to the right of this a rounded eminence, the tuber
omentale, which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of the
lesser omentum. The under surface of the right lobe is divided into two unequal portions by the fossa for the gall-bladder;
the portion to the left, the smaller of the two, is the quadrate lobe, and is in relation with the pyloric end of the stomach, the
superior portion of the duodenum, and the transverse colon. The portion of the under surface of the right lobe to the right of
the fossa for the gall-bladder presents two impressions, one situated behind the other, and separated by a ridge. The anterior
of these two impressions, the colic impression, is shallow and is produced by the right colic flexure; the posterior, the renal
impression, is deeper and is occupied by the upper part of the right kidney and lower part of the right suprarenal gland. Medial to the renal impression is a third and slightly marked impression, lying between it and the neck of the gall-bladder.
This is caused by the descending portion of the duodenum, and is known as the duodenal impression. Just in front of the
inferior vena cava is a narrow strip of liver tissue, the caudate process, which connects the right inferior angle of the caudate lobe to the under surface of the right lobe. It forms the upper boundary of the epiploic foramen of the peritoneum.
The posterior surface (facies posterior) is rounded and broad behind the right lobe, but narrow on the left. Over a large
part of its extent it is not covered by peritoneum; this uncovered portion is about 7.5 cm. broad at its widest part, and is in
direct contact with the diaphragm. It is marked off from the upper surface by the line of reflection of the upper layer of the
coronary ligament, and from the under surface by the line of reflection of the lower layer of the coronary ligament. The
central part of the posterior surface presents a deep concavity which is moulded on the vertebral column and crura of the
diaphragm. To the right of this the inferior vena cava is lodged in its fossa between the uncovered area and the caudate
lobe. Close to the right of this fossa and immediately above the renal impression is a small triangular depressed area, the
suprarenal impression, the greater part of which is devoid of peritoneum; it lodges the right suprarenal gland. To the left of
the inferior vena cava is the caudate lobe, which lies between the fossa for the vena cava and the fossa for the ductus venosus. Its lower end projects and forms part of the posterior boundary of the porta; on the right, it is connected with the under
surface of the right lobe of the liver by theee caudate process, and on the left it presents an elevation, the papillary process.
Its posterior surface rests upon the diaphragm, being separated from it merely by the upper part of the omental bursa. To
the left of the fossa for the ductus venosus is a groove in which lies the antrum cardiacum of the esophagus.
The anterior border (margo anterior) is thin and sharp, and marked opposite the attachment of the falciform ligament by a
deep notch, the umbilical notch, and opposite the cartilage of the ninth rib by a second notch for the fundus of the gallbladder. In adult males this border generally corresponds with the lower margin of the thorax in the right mammillary line;
but in women and children it usually projects below the ribs.
The left extremity of the liver is thin and flattened from above downward.
Fossae. - The left sagittal fossa (fossa sagittalis sinistra; longitudinal fissure) is a deep groove, which extends from the
notch on the anterior margin of the liver to the upper border of the posterior surface of the organ; it separates the right and
left lobes. The porta joins it, at right angles, and divides it into two parts. The anterior part, or fossa for the umbilical vein,
lodges the umbilical vein in the fetus, and its remains (the ligamentum teres) in the adult; it lies between the quadrate lobe
and the left lobe of the liver, and is often partially bridged over by a prolongation of the hepatic substance, the pons hepatis.
The posterior part, or fossa for the ductus venosus, lies between the left lobe and the caudate lobe; it lodges in the fetus, the
ductus venosus, and in the adult a slender fibrous cord, the ligamentum venosum, the obliterated remains of that vessel.
The porta or transverse fissure (porta hepatis) is a short but deep fissure, about 5 cm. long, extending transversely across
the under surface of the left portion of the right lobe, nearer its posterior surface than its anterior border. It joins nearly at
right angles with the left sagittal fossa, and separates the quadrate lobe in front from the caudate lobe and process behind. It
transmits the portal vein, the hepatic artery and nerves, and the hepatic duct and lymphatics. The hepatic duct lies in front
and to the right, the hepatic artery to the left, and the portal vein behind and between the duct and artery.
The fossa for the gall-bladder (fossa vesicae felleae) is a shallow, oblong fossa, placed on the under surface of the right
lobe, parallel with the left sagittal fossa. It extends from the anterior free margin of the liver, which is notched by it, to the
right extremity of the porta. The fossa for the inferior vena cava (fossa venae cavae) is a short deep depression, occasionally a complete canal in consequence of the substance of the liver surrounding the vena cava. It extends obliquely upward on
the posterior surface between the caudate lobe and the bare area of the liver, and is separated from the porta by the caudate
process. On slitting open the inferior vena cava the orifices of the hepatic veins will be seen opening into this vessel at its
upper part, after perforating the floor of this fossa.
Lobes. - The right lobe (lobus hepatis dexter) is much larger than the left; the proportion between them being as six to one.
It occupies the right hypochondrium, and is separated from the left lobe on its upper surface by the falciform ligament; on
its under and posterior surfaces by the left sagittal fossa; and in front by the umbilical notch. It is of a somewhat quadrilateral form, its under and posterior surfaces being marked by three fossae: the porta and the fossae for the gall-bladder and
inferior vena cava, which separate its left part into two smaller lobes; the quadrate and caudate lobes. The impressions on
the right lobe have already been described.
The quadrate lobe (lobus quadratus) is situated on the under surface of the right lobe, bounded in front by the anterior
margin of the liver; behind by the porta; on the right, by the fossa for the gall-bladder; and on the left, by the fossa for the
umbilical vein. It is oblong in shape, its antero-posterior diameter being greater than its transverse.
The caudate lobe (lobus caudatus; Spigelian lobe) is situated upon the posterior surface of the right lobe of the liver, opposite the tenth and eleventh thoracic vertebrae. It is bounded, below, by the porta; on the right, by the fossa for the inferior
vena cava; and, on the left, by the fossa for the ductus venosus. It looks backward, being nearly vertical in position; it is
longer from above downward than from side to side, and is somewhat concave in the transverse direction. The caudate process is a small elevation of the hepatic substance extending obliquely lateralward, from the lower extremity of the caudate
lobe to the under surface of the right lobe. It is situated behind the porta, and separates the fossa for the gall-bladder from
the commencement of the fossa for the inferior vena cava.
The left lobe (lobus hepatis sinister) is smaller and more flattened than the right. It is situated in the epigastric and left
hypochondriac regions. Its upper surface is slightly convex and is moulded on to the diaphragm; its under surface presents
the gastric impression and omental tuberosity.
Ligaments. - The liver is connected to the under surface of the diaphragm and to the anterior wall of the abdomen by five
ligaments; four of these - the falciform, the coronary, and the two lateral - are peritoneal folds; the fifth, the round ligament,
is a fibrous cord, the obliterated umbilical vein. The liver is also attached to the lesser curvature of the stomach by the hepatogastric and to the duodenum by the hepatoduodenal ligament.
The falciform ligament (ligamentum falciforme hepatis) is a broad and thin antero-posterior peritoneal fold, falciform in
shape, its base being directed downward and backward, its apex upward and backward. It is situated in an antero-posterior
plane, but lies obliquely so that one surface faces forward and is in contact with the peritoneum behind the right Rectus and
the diaphragm, while the other is directed backward and is in contact with the left lobe of the liver. It is attached by its left
margin to the under surface of the diaphragm, and the posterior surface of the sheath of the right Rectus as low down as the
umbilicus; by its right margin it extends from the notch on the anterior margin of the liver, as far back as the posterior surface. It is composed of two layers of peritoneum closely united together. Its base or free edge contains between its layers
the round ligament and the parumbilical veins.
The coronary ligament (ligamentum coronarium hepatis) consists of an upper and a lower layer. The upper layer is
formed by the reflection of the peritoneum from the upper margin of the bare area of the liver to the under surface of the
diaphragm, and is continuous with the right layer of the falciform ligament. The lower layer is reflected from the lower
margin of the bare area on to the right kidney and suprarenal gland, and is termed the hepatorenal ligament.
The triangular ligaments (lateral ligaments) are two in number, right and left. The right triangular ligament (ligamentum
triangulare dextrum) is situated at the right extremity of the bare area, and is a small fold which passes to the diaphragm,
being formed by the apposition of the upper and lower layers of the coronary ligament. The left triangular ligament (ligamentum triangulare sinistrum) is a fold of some considerable size, which connects the posterior part of the upper surface of
the left lobe to the diaphragm; its anterior layer is continuous with the left layer of the falciform ligament.
The round ligament (ligamentum teres hepatis) is a fibrous cord resulting from the obliteration of the umbilical vein. It
ascends from the umbilicus, in the free margin of the falciform ligament, to the umbilical notch of the liver, from which it
may be traced in its proper fossa on the inferior surface of the liver to the porta, where it becomes continuous with the ligamentum venosum.
Fixation of the Liver. - Several factors contribute to maintain the liver in place. The attachments of the liver to the diaphragm by the coronary and triangular ligaments and the intervening connective tissue of the uncovered area, together with
the intimate connection of the inferior vena cava by the connective tissue and hepatic veins would hold up the posterior part
of the liver. Some support is derived from the pressure of the abdominal viscera which completely fill the abdomen whose
muscular walls are always in a state of tonic contraction. The superior surface of the liver is perfectly fitted to the under
surface of the diaphragm so that atmospheric pressure alone would be enough to hold it against the diaphragm. The latter in
turn is held up by the negative pressure in the thorax. The lax falciform ligament certainly gives no support though it probably limits lateral displacement.
Development. - The liver arises in the form of a diverticulum or hollow outgrowth from the ventral surface of that portion
of the gut which afterward becomes the descending part of the duodenum. This diverticulum is lined by entoderm, and
grows upward and forward into the septum transversum, a mass of mesoderm between the vitelline duct and the pericardial
cavity, and there gives off two solid buds of cells which represent the right and the left lobes of the liver. The solid buds of
cells grow into columns or cylinders, termed the hepatic cylinders, which branch and anastomose to form a close meshwork. This network invades the vitelline and umbilical veins, and breaks up these vessels into a series of capillary-like vessels termed sinusoids (Minot), which ramify in the meshes of the cellular network and ultimately form the venous capillaries of the liver. By the continued growth and ramification of the hepatic cylinders the mass of the liver is gradually formed.
The original diverticulum from the duodenum forms the common bileduct, and from this the cystic duct and gall-bladder
arise as a solid outgrowth which later acquires a lumen. The opening of the common duct is at first in the ventral wall of the
duodenum; later, owing to the rotation of the gut, the opening is carried to the left and then dorsalward to the position it
occupies in the adult.
As the liver undergoes enlargement, both it and the ventral mesogastrium of the fore-gut are gradually differentiated from
the septum transversum; and from the under surface of the latter the liver projects downward into the abdominal cavity. By
the growth of the liver the ventral mesogastrium is divided into two parts, of which the anterior forms the falciform and
coronary ligaments, and the posterior the lesser omentum. About the third month the liver almost fills the abdominal cavity,
and its left lobe is nearly as large as its right. From this period the relative development of the liver is less active, more especially that of the left lobe, which actually undergoes some degeneration and becomes smaller than the right; but up to the
end of fetal life the liver remains relatively larger than in the adult.
The Hepatic Duct (ductus hepaticus). - Two main trunks of nearly equal size issue from the liver at the porta, one from
the right, the other from the left lobe; these unite to form the hepatic duct, which passes downward and to the right for
about 4 cm., between the layers of the lesser omentum, where it is joined at an acute angle by the cystic duct, and so forms
the common bile duct. The hepatic duct is accompanied by the hepatic artery and portal vein.
The Gall-bladder (vesica fellae) - The gall-bladder is a conical or pear-shaped musculomembranous sac, lodged in a
fossa on the under surface of the right lobe of the liver, and extending from near the right extremity of the porta to the anterior border of the organ. It is from 7 to 10 cm. in length, 2.5 cm. in breadth at its widest part, and holds from 30 to 35 c.c. It
is divided into a fundus, body, and neck. The fundus, or broad extremity, is directed downward, forward, and to the right,
and projects beyond the anterior border of the liver; the body and neck are directed upward and backward to the left. The
upper surface of the gall-bladder is attached to the liver by connective tissue and vessels. The under surface is covered by
peritoneum, which is reflected on to it from the surface of the liver. Occasionally the whole of the organ is invested by the
serous membrane, and is then connected to the liver by a kind of mesentery.
Relations. - The body is in relation, by its upper surface, with the liver; by its under surface, with the commencement of the
transverse colon; and farther back usually with the upper end of the descending portion of the duodenum, but sometimes
with the superior portion of the duodenum or pyloric end of the stomach. The fundus is completely invested by peritoneum;
it is in relation, in front, with the abdominal parietes, immediately below the ninth costal cartilage; behind with the transverse colon. The neck is narrow, and curves upon itself like the letter S; at its point of connection with the cystic duct it
presents a well-marked constriction.
Structure. - The gall-bladder consists of three coats: serous, fibromuscular, and mucous.
The external or serous coat (tunica serosa vesicae felleae) is derived from the peritoneum; it completely invests the fundus, but covers the body and neck only on their under surfaces.
The fibromuscular coat (tunica muscularis vesicae felleae), a thin but strong layer forming the frame-work of the sac,
consists of dense fibrous tissue, which interlaces in all directions, and is mixed with plain muscular fibers, disposed chiefly
in a longitudinal direction, a few running transversely.
The internal or mucous coat (tunica mucosa vesicae felleae) is loosely connected with the fibrous layer. It is generally of
a yellowish-brown color, and is elevated into minute rugae. Opposite the neck of the gall-bladder the mucous membrane
projects inward in the form of oblique ridges or folds, forming a sort of spiral valve.
The mucous membrane is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver,
and through the common bile duct with the mucous membrane of the duodenum. It is covered with columnar epithelium,
and secretes mucin; in some animals it secretes a nucleoprotein instead of mucin.
The Cystic Duct (ductus cysticus). - The cystic duct about 4 cm. long, runs backward, downward, and to the left from the
neck of the gall-bladder, and joins the hepatic duct to form the common bile duct. The mucous membrane lining its interior
is thrown into a series of crescentic folds, from five to twelve in number, similar to those found in the neck of the gallbladder. They project into the duct in regular succession, and are directed obliquely around the tube, presenting much the
appearance of a continuous spiral valve. When the duct is distended, the spaces between the folds are dilated, so as to give
to its exterior a twisted appearance.
The Common Bile Duct (ductus choledochus). - The common bile duct is formed by the junction of the cystic and hepatic ducts; it is about 7.5 cm. long, and of the diameter of a goose-quill.
It descends along the right border of the lesser omentum behind the superior portion of the duodenum, in front of the portal vein, and to the right of the hepatic artery; it then runs in a groove near the right border of the posterior surface of the
head of the pancreas; here it is situated in front of the inferior vena cava, and is occasionally completely imbedded in the
pancreatic substance. At its termination it lies for a short distance along the right side of the terminal part of the pancreatic
duct and passes with it obliquely between the mucous and muscular coats. The two ducts unite and open by a common orifice upon the summit of the duodenal papilla, situated at the medial side of the descending portion of the duodenum, a little
below its middle and about 7 to 10 cm. from the pylorus. The short tube formed by the union of the two ducts is dilated into
an ampulla, the ampulla of Vater.
Structure. - The coats of the large biliary ducts are an external or fibrous, and an internal or mucous. The fibrous coat is
composed of strong fibroareolar tissue, with a certain amount of muscular tissue, arranged, for the most part, in a circular
manner around the duct. The mucous coat is continuous with the lining membrane of the hepatic ducts and gall-bladder,
and also with that of the duodenum; and, like the mucous membrane of these structures, its epithelium is of the columnar
variety. It is provided with numerous mucous glands, which are lobulated and open by minute orifices scattered irregularly
in the larger ducts.
The pancreas is a compound racemose gland, analogous in its structures to the salivary glands, though softer and less
compactly arranged than those organs. Its secretion, the pancreatic juice, carried by the pancreatic duct to the duodenum, is
an important digestive fluid. In addition the pancreas has an important internal secretion, probably elaborated by the cells of
Langerhans, which is taken up by the blood stream and is concerned with sugar metabolism. It is long and irregularly prismatic in shape; its right extremity, being broad, is called the head, and is connected to the main portion of the organ, or
body, by a slight constriction, the neck; while its left extremity gradually tapers to form the tail. It is situated transversely
across the posterior wall of the abdomen, at the back of the epigastric and left hypochondriac regions. Its length varies from
12.5 to 15 cm., and its weight from 60 to 100 gm.
Relations. - The Head (caput pancreatis) is flattened from before backward, and is lodged within the curve of the duodenum. Its upper border is overlapped by the superior part of the duodenum and its lower overlaps the horizontal part; its right
and left borders overlap in front, and insinuate themselves behind, the descending and ascending parts of the duodenum
respectively. The angle of junction of the lower and left lateral borders forms a prolongation, termed the uncinate process.
In the groove between the duodenum and the right lateral and lower borders in front are the anastomosing superior and inferior pancreaticoduodenal arteries; the common bile duct descends behind, close to the right border, to its termination in
the descending part of the duodenum.
Anterior Surface. - The greater part of the right half of this surface is in contact with the transverse colon, only areolar tissue intervening. From its upper part the neck springs, its right limit being marked by a groove for the gastroduodenal artery.
The lower part of the right half, below the transverse colon, is covered by peritoneum continuous with the inferior layer of
the transverse mesocolon, and is in contact with the coils of the small intestine. The superior mesenteric artery passes down
in front of the left half across the uncinate process; the superior mesenteric vein runs upward on the right side of the artery
and, behind the neck, joins with the lienal vein to form the portal vein.
Posterior Surface. - The posterior surface is in relation with the inferior vena cava, the common bile duct, the renal veins,
the right crus of the diaphragm, and the aorta.
The Neck springs from the right upper portion of the front of the head. It is about 2.5 cm. long, and is directed at first upward and forward, and then upward and to the left to join the body; it is somewhat flattened from above downward and
backward. Its antero-superior surface supports the pylorus; its postero-inferior surface is in relation with the commencement of the portal vein; on the right it is grooved by the gastroduodenal artery.
The Body (corpus pancreatis) is somewhat prismatic in shape, and has three surfaces: anterior, posterior, and inferior.
The anterior surface (facies anterior) is somewhat concave; and is directed forward and upward: it is covered by the postero-inferior surface of the stomach which rests upon it, the two organs being separated by the omental bursa. Where it
joins the neck there is a well-marked prominence, the tuber omentale, which abuts against the posterior surface of the lesser
omentum.
The posterior surface (facies posterior) is devoid of peritoneum, and is in contact with the aorta, the lienal vein, the left
kidney and its vessels, the left suprarenal gland, the origin of the superior mesenteric artery, and the crura of the diaphragm.
The inferior surface (facies inferior) is narrow on the right but broader on the left, and is covered by peritoneum; it lies
upon the duodenojejunal flexure and on some coils of the jejunum; its left extremity rests on the left colic flexure.
The superior border (margo superior) is blunt and flat to the right; narrow and sharp to the left, near the tail. It commences on the right in the omental tuberosity, and is in relation with the celiac artery, from which the hepatic artery courses to
the right just above the gland, while the lienal artery runs toward the left in a groove along this border.
The anterior border (margo anterior) separates the anterior from the inferior surface, and along this border the two layers
of the transverse mesocolon diverge from one another; one passing upward over the anterior surface, the other backward
over the inferior surface.
The inferior border (margo inferior) separates the posterior from the inferior surface; the superior mesenteric vessels
emerge under its right extremity.
The Tail (cauda pancreatis) is narrow; it extends to the left as far as the lower part of the gastric surface of the spleen,
lying in the phrenicolienal ligament, and it is in contact with the left colic flexure.
The Pancreatic Duct (ductus pancreaticus [Wirsungi]; duct of Wirsung) extends transversely from left to right
through the substance of the pancreas. It commences by the junction of the small ducts of the lobules situated in the tail of
the pancreas, and, running from left to right through the body, it receives the ducts of the various lobules composing the
gland. Considerably augmented in size, it reaches the neck, and turning downward, backward, and to the right, it comes
into relation with the common bile duct, which lies to its right side; leaving the head of the gland, it passes very obliquely
through the mucous and muscular coats of the duodenum, and ends by an orifice common to it and the common bile duct
upon the summit of the duodenal papilla, situated at the medial side of the descending portion of the duodenum, 7.5 to 10
cm. below the pylorus. The pancreatic duct, near the duodenum, is about the size of an ordinary quill. Sometimes the pancreatic duct and the common bile duct open separately into the duodenum. Frequently there is an additional duct, which is
given off from the pancreatic duct in the neck of the pancreas and opens into the duodenum about 2.5 cm. above the duodenal papilla. It receives the ducts from the lower part of the head, and is known as the accessory pancreatic duct (duct of
Santorini).
Development. - The pancreas is developed in two parts, a dorsal and a ventral. The former arises as a diverticulum from the
dorsal aspect of the duodenum a short distance above the hepatic diverticulum, and, growing upward and backward into the
dorsal mesogastrium, forms a part of the head and uncinate process and the whole of the body and tail of the pancreas. The
ventral part appears in the form of a diverticulum from the primitive bile-duct and forms the remainder of the head and uncinate process of the pancreas. The duct of the dorsal part (accessory pancreatic duct) therefore opens independently into
the duodenum, while that of the ventral part (pancreatic duct) opens with the common bile-duct. About the sixth week the
two parts of the pancreas meet and fuse and a communication is established between their ducts. After this has occurred the
terminal part of the accessory duct, i. e., the part between the duodenum and the point of meeting of the two ducts, undergoes little or no enlargement, while the pancreatic duct increases in size and forms the main duct of the gland. The opening
of the accessory duct into the duodenum is sometimes obliterated, and even when it remains patent it is probable that the
whole of the pancreatic secretion is conveyed through the pancreatic duct.
At first the pancreas is directed upward and backward between the two layers of the dorsal mesogastrium, which give to it
a complete peritoneal investment, and its surfaces look to the right and left. With the change in the position of the stomach
the dorsal mesogastrium is drawn downward and to the left, and the right side of the pancreas is directed backward and the
left forward. The right surface becomes applied to the posterior abdominal wall, and the peritoneum which covered it undergoes absorption; and thus, in the adult, the gland appears to lie behind the peritoneal cavity.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on sample:
Practice class 6. Peritoneum, its topography, development, relations to organs.
The aim: to learn the structure, development and relations of the serous membrane of abdominal cavity.
Professional orientation: knowledge of this topic is essential for all medical practitioners, especially gastroenterologists, abdominal surgeons and therapeutists.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Peritoneum (Tunica Serosa) - The peritoneum is the largest serous membrane in the body, and consists, in the male,
of a closed sac, a part of which is applied against the abdominal parietes, while the remainder is reflected over the contained viscera. In the female the peritoneum is not a closed sac, since the free ends of the uterine tubes open directly into
the peritoneal cavity. The part which lines the parietes is named the parietal portion of the peritoneum; that which is reflected over the contained viscera constitutes the visceral portion of the peritoneum. The free surface of the membrane is
smooth, covered by a layer of flattened mesothelium, and lubricated by a small quantity of serous fluid. Hence the viscera
can glide freely against the wall of the cavity or upon one another with the least possible amount of friction. The attached
surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue, termed the subserous areolar tissue. The parietal portion is loosely connected with the fascial lining of the abdomen and pelvis, but is
more closely adherent to the under surface of the diaphragm, and also in the middle line of the abdomen.
The space between the parietal and visceral layers of the peritoneum is named the peritoneal cavity; but under normal
conditions this cavity is merely a potential one, since the parietal and visceral layers are in contact. The peritoneal cavity
gives off a large diverticulum, the omental bursa, which is situated behind the stomach and adjoining structures; the neck of
communication between the cavity and the bursa is termed the epiploic foramen (foramen of Winslow). Formerly the main
portion of the cavity was described as the greater, and the omental bursa as the lesser sac.
The peritoneum differs from the other serous membranes of the body in presenting a much more complex arrangement,
and one that can be clearly understood only by following the changes which take place in the digestive tube during its development.
To trace the membrane from one viscus to another, and from the viscera to the parietes, it is necessary to follow its continuity in the vertical and horizontal directions, and it will be found simpler to describe the main portion of the cavity and the
omental bursa separately.
Vertical Disposition of the Main Peritoneal Cavity (greater sac). - It is convenient to trace this from the back of the abdominal wall at the level of the umbilicus. On following the peritoneum upward from this level it is seen to be reflected
around a fibrous cord, the ligamentum teres (obliterated umbilical vein), which reaches from the umbilicus to the under
surface of the liver. This reflection forms a somewhat triangular fold, the falciform ligament of the liver, attaching the upper and anterior surfaces of the liver to the diaphragm and abdominal wall. With the exception of the line of attachment of
this ligament the peritoneum covers the whole of the under surface of the anterior part of the diaphragm, and is continued
from it on to the upper surface of the right lobe of the liver as the superior layer of the coronary ligament, and on to the
upper surface of the left lobe as the superior layer of the left triangular ligament of the liver. Covering the upper and anterior surfaces of the liver, it is continued around its sharp margin on to the under surface, where it presents the following relations: (a) It covers the under surface of the right lobe and is reflected from the back part of this on to the right suprarenal
gland and upper extremity of the right kidney, forming in this situation the inferior layer of the coronary ligament; a special
fold, the hepatorenal ligament, is frequently present between the inferior surface of the liver and the front of the kidney.
From the kidney it is carried downward to the duodenum and right colic flexure and medialward in front of the inferior
vena cava, where it is continuous with the posterior wall of the omental bursa. Between the two layers of the coronary ligament there is a large triangular surface of the liver devoid of peritoneal covering; this is named the bare area of the liver,
and is attached to the diaphragm by areolar tissue. Toward the right margin of the liver the two layers of the coronary ligament gradually approach each other, and ultimately fuse to form a small triangular fold connecting the right lobe of the
liver to the diaphragm, and named the right triangular ligament of the liver. The apex of the triangular bare area corre-
sponds with the point of meeting of the two layers of the coronary ligament, its base with the fossa for the inferior vena
cava. (b) It covers the lower surface of the quadrate lobe, the under and lateral surfaces of the gall-bladder, and the under
surface and posterior border of the left lobe; it is then reflected from the upper surface of the left lobe to the diaphragm as
the inferior layer of the left triangular ligament, and from the porta of the liver and the fossa for the ductus venosus to the
lesser curvature of the stomach and the first 2.5 cm. of the duodenum as the anterior layer of the hepatogastric and hepatoduodenal ligaments, which together constitute the lesser omentum. If this layer of the lesser omentum be followed to the
right it will be found to turn around the hepatic artery, bile duct, and portal vein, and become continuous with the anterior
wall of the omental bursa, forming a free folded edge of peritoneum. Traced downward, it covers the antero-superior surface of the stomach and the commencement of the duodenum, and is carried down into a large free fold, known as the gastrocolic ligament or greater omentum. Reaching the free margin of this fold, it is reflected upward to cover the under and
posterior surfaces of the transverse colon, and thence to the posterior abdominal wall as the inferior layer of the transverse
mesocolon. It reaches the abdominal wall at the head and anterior border of the pancreas, is then carried down over the
lower part of the head and over the inferior surface of the pancreas on the superior mesenteric vessels, and thence to the
small intestine as the anterior layer of the mesentery. It encircles the intestine, and subsequently may be traced, as the posterior layer of the mesentery, upward and backward to the abdominal wall. From this it sweeps down over the aorta into the
pelvis, where it invests the sigmoid colon, its reduplication forming the sigmoid mesocolon. Leaving first the sides and then
the front of the rectum, it is reflected on to the seminal vesicles and fundus of the urinary bladder and, after covering the
upper surface of that viscus, is carried along the medial and lateral umbilical ligaments on to the back of the abdominal wall
to the level from which a start was made.
Between the rectum and the bladder it forms, in the male, a pouch, the rectovesical excavation, the bottom of which is
slightly below the level of the upper ends of the vesiculae seminales - i. e., about 7.5 cm. from the orifice of the anus. When
the bladder is distended, the peritoneum is carried up with the expanded viscus so that a considerable part of the anterior
surface of the latter lies directly against the abdominal wall without the intervention of peritoneal membrane (prevesical
space of Retzius). In the female the peritoneum is reflected from the rectum over the posterior vaginal fornix to the cervix
and body of the uterus, forming the rectouterine excavation (pouch of Douglas). It is continued over the intestinal surface
and fundus of the uterus on to its vesical surface, which it covers as far as the junction of the body and cervix uteri, and
then to the bladder, forming here a second, but shallower, pouch, the vesicouterine excavation. It is also reflected from the
sides of the uterus to the lateral walls of the pelvis as two expanded folds, the broad ligaments of the uterus, in the free
margin of each of which is the uterine tube.
Vertical Disposition of the Omental Bursa (lesser peritoneal sac) - A start may be made in this case on the posterior abdominal wall at the anterior border of the pancreas. From this region the peritoneum may be followed upward over the pancreas on to the inferior surface of the diaphragm, and thence on to the caudate lobe and caudate process of the liver to the
fossa from the ductus venosus and the porta of the liver. Traced to the right, it is continuous over the inferior vena cava
with the posterior wall of the main cavity. From the liver it is carried downward to the lesser curvature of the stomach and
the commencement of the duodenum as the posterior layer of the lesser omentum, and is continuous on the right, around
the hepatic artery, bile duct, and portal vein, with the anterior layer of this omentum. The posterior layer of the lesser omentum is carried down as a covering for the postero-inferior surfaces of the stomach and commencement of the duodenum,
and is continued downward as the deep layer of the gastrocolic ligament or greater omentum. From the free margin of this
fold it is reflected upward on itself to the anterior and superior surfaces of the transverse colon, and thence as the superior
layer of the transverse mesocolon to the anterior border of the pancreas, the level from which a start was made. It will be
seen that the loop formed by the wall of the omental bursa below the transverse colon follows, and is closely applied to, the
deep surface of that formed by the peritoneum of the main cavity, and that the greater omentum or large fold of peritoneum
which hangs in front of the small intestine therefore consists of four layers, two anterior and two posterior separated by the
potential cavity of the omental bursa.
Horizontal Disposition of the Peritoneum. - Below the transverse colon the arrangement is simple, as it includes only the
main cavity; above the level of the transverse colon it is more complicated on account of the existence of the omental bursa.
Below the transverse colon it may be considered in the two regions, viz., in the pelvis and in the abdomen proper.
(1) In the Pelvis. - The peritoneum here follows closely the surfaces of the pelvic viscera and the inequalities of the pelvic
walls, and presents important differences in the two sexes. (a) In the male it encircles the sigmoid colon, from which it is
reflected to the posterior wall of the pelvis as a fold, the sigmoid mesocolon. It then leaves the sides and, finally, the front
of the rectum, and is continued on to the upper ends of the seminal vesicles and the bladder; on either side of the rectum it
forms a fossa, the pararectal fossa, which varies in size with the distension of the rectum. In front of the rectum the peritoneum forms the rectovesical excavation, which is limited laterally by peritoneal folds extending from the sides of the bladder to the rectum and sacrum. These folds are known from their position as the rectovesical or sacrogenital folds. The peritoneum of the anterior pelvic wall covers the superior surface of the bladder, and on either side of this viscus forms a depression, termed the paravesical fossa, which is limited laterally by the fold of peritoneum covering the ductus deferens.
The size of this fossa is dependent on the state of distension of the bladder; when the bladder is empty, a variable fold of
peritoneum, the plica vesicalis transversa, divides the fossa into two portions. On the peritoneum between the paravesical
and pararectal fossae the only elevations are those produced by the ureters and the hypogastric vessels. (b) In the female,
pararectal and paravesical fossae similar to those in the male are present: the lateral limit of the paravesical fossa is the
peritoneum investing the round ligament of the uterus. The rectovesical excavation is, however, divided by the uterus and
vagina into a small anterior vesicouterine and a large, deep, posterior rectouterine excavation. The sacrogenital folds form
the margins of the latter, and are continued on to the back of the uterus to form a transverse fold, the torus uterinus. The
broad ligaments extend from the sides of the uterus to the lateral walls of the pelvis; they contain in their free margins the
uterine tubes, and in their posterior layers the ovaries. Below, the broad ligaments are continuous with the peritoneum on
the lateral walls of the pelvis. On the lateral pelvic wall behind the attachment of the broad ligament, in the angle between
the elevations produced by the diverging hypogastric and external iliac vessels is a slight fossa, the ovarian fossa, in which
the ovary normally lies.
(2) In the Lower Abdomen - Starting from the linea alba, below the level of the transverse colon, and tracing the continuity
of the peritoneum in a horizontal direction to the right, the membrane covers the inner surface of the abdominal wall almost
as far as the lateral border of the Quadratus lumborum; it encloses the cecum and vermiform process, and is reflected over
the sides and front of the ascending colon; it may then be traced over the duodenum, Psoas major, and inferior vena cava
toward the middle line, whence it passes along the mesenteric vessels to invest the small intestine, and back again to the
large vessels in front of the vertebral column, forming the mesentery, between the layers of which are contained the mesenteric bloodvessels, lacteals, and glands. It is then continued over the left Psoas; it covers the sides and front of the descending colon, and, reaching the abdominal wall, is carried on it to the middle line.
(3) In the Upper Abdomen - Above the transverse colon the omental bursa is superadded to the general sac, and the communication of the two cavities with one another through the epiploic foramen can be demonstrated.
(a) Main Cavity. - Commencing on the posterior abdominal wall at the inferior vena cava, the peritoneum may be followed to the right over the front of the suprarenal gland and upper part of the right kidney on to the antero-lateral abdominal wall. From the middle line of the anterior wall a backwardly directed fold encircles the obliterated umbilical vein
and forms the falciform ligament of the liver. Continuing to the left, the peritoneum lines the antero-lateral abdominal wall
and covers the lateral part of the front of the left kidney, and is reflected to the posterior border of the hilus of the spleen as
the posterior layer of the phrenicolienal ligament. It can then be traced around the surface of the spleen to the front of the
hilus, and thence to the cardiac end of the greater curvature of the stomach as the anterior layer of the gastrolienal ligament.
It covers the antero-superior surfaces of the stomach and commencement of the duodenum, and extends up from the lesser
curvature of the stomach to the liver as the anterior layer of the lesser omentum.
(b) Omental Bursa (bursa omentalis; lesser peritoneal sac). - On the posterior abdominal wall the peritoneum of the general cavity is continuous with that of the omental bursa in front of the inferior vena cava. Starting from here, the bursa may
be traced across the aorta and over the medial part of the front of the left kidney and diaphragm to the hilus of the spleen as
the anterior layer of the phrenicolienal ligament. From the spleen it is reflected to the stomach as the posterior layer of the
gastrosplenic ligament. It covers the postero-inferior surfaces of the stomach and commencement of the duodenum, and
extends upward to the liver as the posterior layer of the lesser omentum; the right margin of this layer is continuous around
the hepatic artery, bile duct, and portal vein, with the wall of the general cavity.
The epiploic foramen (foramen epiploicum; foramen of Winslow) is the passage of communication between the general
cavity and the omental bursa. It is bounded in front by the free border of the lesser omentum, with the common bile duct,
hepatic artery, and portal vein between its two layers; behind by the peritoneum covering the inferior vena cava; above by
the peritoneum on the caudate process of the liver, and below by the peritoneum covering the commencement of the duodenum and the hepatic artery, the latter passing forward below the foramen before ascending between the two layers of the
lesser omentum.
The boundaries of the omental bursa will now be evident. It is bounded in front, from above downward, by the caudate
lobe of the liver, the lesser omentum, the stomach, and the anterior two layers of the greater omentum. Behind, it is limited,
from below upward, by the two posterior layers of the greater omentum, the transverse colon, and the ascending layer of
the transverse mesocolon, the upper surface of the pancreas, the left suprarenal gland, and the upper end of the left kidney.
To the right of the esophageal opening of the stomach it is formed by that part of the diaphragm which supports the caudate
lobe of the liver. Laterally, the bursa extends from the epiploic foramen to the spleen, where it is limited by the phrenicolienal and gastrolienal ligaments.
The omental bursa, therefore, consists of a series of pouches or recesses to which the following terms are applied: (1) the
vestibule, a narrow channel continued from the epiploic foramen, over the head of the pancreas to the gastropancreatic fold;
this fold extends from the omental tuberosity of the pancreas to the right side of the fundus of the stomach, and contains the
left gastric artery and coronary vein; (2) the superior omental recess, between the caudate lobe of the liver and the diaphragm; (3) the lienal recess, between the spleen and the stomach; (4) the inferior omental recess, which comprises the remainder of the bursa.
In the fetus the bursa reaches as low as the free margin of the greater omentum, but in the adult its vertical extent is usually more limited owing to adhesions between the layers of the omentum. During a considerable part of fetal life the transverse colon is suspended from the posterior abdominal wall by a mesentery of its own, the two posterior layers of the greater omentum passing at this stage in front of the colon. This condition occasionally persists throughout life, but as a rule
adhesion occurs between the mesentery of the transverse colon and the posterior layer of the greater omentum, with the
result that the colon appears to receive its peritoneal covering by the splitting of the two posterior layers of the latter fold.
In the adult the omental bursa intervenes between the stomach and the structures on which that viscus lies, and performs
therefore the functions of a serous bursa for the stomach.
Numerous peritoneal folds extend between the various organs or connect them to the parietes; they serve to hold the viscera in position, and, at the same time, enclose the vessels and nerves proceeding to them. They are grouped under the three
headings of ligaments, omenta, and mesenteries.
There are two omenta, the lesser and the greater.
The lesser omentum (omentum minus; small omentum; gastrohepatic omentum) is the duplicature which extends to the
liver from the lesser curvature of the stomach and the commencement of the duodenum. It is extremely thin, and is continuous with the two layers of peritoneum which cover respectively the antero-superior and postero-inferior surfaces of the
stomach and first part of the duodenum. When these two layers reach the lesser curvature of the stomach and the upper
border of the duodenum, they join together and ascend as a double fold to the porta of the liver; to the left of the porta the
fold is attached to the bottom of the fossa for the ductus venosus, along which it is carried to the diaphragm, where the two
layers separate to embrace the end of the esophagus. At the right border of the omentum the two layers are continuous, and
form a free margin which constitutes the anterior boundary of the epiploic foramen. The portion of the lesser omentum extending between the liver and stomach is termed the hepatogastric ligament, while that between the liver and duodenum is
the hepatoduodenal ligament. Between the two layers of the lesser omentum, close to the right free margin, are the hepatic
artery, the common bile duct, the portal vein, lymphatics, and the hepatic plexus of nerves - all these structures being enclosed in a fibrous capsule (Glisson’s capsule). Between the layers of the lesser omentum, where they are attached to the
stomach, run the right and left gastric vessels.
The greater omentum (omentum majus; great omentum; gastrocolic omentum) is the largest peritoneal fold. It consists of
a double sheet of peritoneum, folded on itself so that it is made up of four layers. The two layers which descend from the
stomach and commencement of the duodenum pass in front of the small intestines, sometimes as low down as the pelvis;
they then turn upon themselves, and ascend again as far as the transverse colon, where they separate and enclose that part
of the intestine. These individual layers may be easily demonstrated in the young subject, but in the adult they are more or
less inseparably blended. The left border of the greater omentum is continuous with the gastrolienal ligament; its right border extends as far as the commencement of the duodenum. The greater omentum is usually thin, presents a cribriform appearance, and always contains some adipose tissue, which in fat people accumulates in considerable quantity. Between its
two anterior layers, a short distance from the greater curvature of the stomach, is the anastomosis between the right and left
gastroepiploic vessels.
The mesenteries are: the mesentery proper, the transverse mesocolon, and the sigmoid mesocolon. In addition to these
there are sometimes present an ascending and a descending mesocolon.
The mesentery proper (mesenterium) is the broad, fan-shaped fold of peritoneum which connects the convolutions of the
jejunum and ileum with the posterior wall of the abdomen. Its root - the part connected with the structures in front of the
vertebral column - is narrow, about 15 cm. long, and is directed obliquely from the duodenojejunal flexure at the left side of
the second lumbar vertebra to the right sacroiliac articulation. Its intestinal border is about 6 metres long; and here the two
layers separate to enclose the intestine, and form its peritoneal coat. It is narrow above, but widens rapidly to about 20 cm.,
and is thrown into numerous plaits or folds. It suspends the small intestine, and contains between its layers the intestinal
branches of the superior mesenteric artery, with their accompanying veins and plexuses of nerves, the lacteal vessels, and
mesenteric lymph glands.
The transverse mesocolon (mesocolon transversum) is a broad fold, which connects the transverse colon to the posterior
wall of the abdomen. It is continuous with the two posterior layers of the greater omentum, which, after separating to surround the transverse colon, join behind it, and are continued backward to the vertebral column, where they diverge in front
of the anterior border of the pancreas. This fold contains between its layers the vessels which supply the transverse colon.
The sigmoid mesocolon (mesocolon sigmoideum) is the fold of peritoneum which retains the sigmoid colon in connection
with the pelvic wall. Its line of attachment forms a V-shaped curve, the apex of the curve being placed about the point of
division of the left common iliac artery. The curve beings on the medial side of the left Psoas major, and runs upward and
backward to the apex, from which it bends sharply downward, and ends in the median plane at the level of the third sacral
vertebra. The sigmoid and superior hemorrhoidal vessels run between the two layers of this fold.
In most cases the peritoneum covers only the front and sides of the ascending and descending parts of the colon. Sometimes, however, these are surrounded by the serous membrane and attached to the posterior abdominal wall by an ascending
and a descending mesocolon respectively. A fold of peritoneum, the phrenicocolic ligament, is continued from the left colic
flexure to the diaphragm opposite the tenth and eleventh ribs; it passes below and serves to support the spleen, and therefore has received the name of sustentaculum lienis.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples.
Practice class 7. Cavities and recesses of peritoneal cavity.
The aim: to learn the cavities and recesses of peritoneal cavity.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, abdominal surgeons etc
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
Peritoneal Recesses or Fossae (retroperitoneal fossae). - In certain parts of the abdominal cavity there are recesses of
peritoneum forming culs-de-sac or pouches, which are of surgical interest in connection with the possibility of the occurrence of “retroperitoneal” herniae. The largest of these is the omental bursa (already described), but several others, of
smaller size, require mention, and may be divided into three groups, viz.: duodenal, cecal, and intersigmoid.
1. Duodenal Fossae - Three are fairly constant, viz.: (a) The inferior duodenal fossa, present in from 70 to 75 per cent. of
cases, is situated opposite the third lumbar vertebra on the left side of the ascending portion of the duodenum. Its opening is
directed upward, and is bounded by a thin sharp fold of peritoneum with a concave margin, called the duodenomesocolic
fold. The tip of the index finger introduced into the fossa under the fold passes some little distance behind the ascending
portion of the duodenum. (b) The superior duodenal fossa, present in from 40 to 50 per cent. of cases, often coexists with
the inferior one, and its orifice looks downward. It lies on the left of the ascending portion of the duodenum, in front of the
second lumbar vertebra, and behind a sickle-shaped fold of peritoneum, the duodenojejunal fold, and has a depth of about 2
cm. (c) The duodenojejunal fossa exists in from 15 to 20 per cent. of cases, but has never yet been found in conjunction
with the other forms of duodenal fossae it can be seen by pulling the jejunum downward and to the right, after the transverse colon has been pulled upward. It is bounded above by the pancreas, to the right by the aorta, and to the left by the
kidney; beneath is the left renal vein. It has a depth of from 2 to 3 cm., and its orifice, directed downward and to the right,
is nearly circular and will admit the tip of the little finger.
2. Cecal Fossae (pericecal folds or fossae). - There are three principal pouches or recesses in the neighborhood of the cecum: (a) The superior ileocecal fossa is formed by a fold of peritoneum, arching over the branch of the ileocolic artery
which supplies the ileocolic junction. The fossa is a narrow chink situated between the mesentery of the small intestine, the
ileum, and the small portion of the cecum behind. (b) The inferior ileocecal fossa is situated behind the angle of junction of
the ileum and cecum. It is formed by the ileocecal fold of peritoneum (bloodless fold of Treves), the upper border of which
is fixed to the ileum, opposite its mesenteric attachment, while the lower border, passing over the ileocecal junction, joins
the mesenteriole of the vermiform process, and sometimes the process itself. Between this fold and the mesenteriole of the
vermiform process is the inferior ileocecal fossa. It is bounded above by the posterior surface of the ileum and the mesentery; in front and below by the ileocecal fold, and behind by the upper part of the mesenteriole of the vermiform process.
(c) The cecal fossa is situated immediately behind the cecum, which has to be raised to bring it into view. It varies much in
size and extent. In some cases it is sufficiently large to admit the index finger, and extends upward behind the ascending
colon in the direction of the kidney; in others it is merely a shallow depression. It is bounded on the right by the cecal fold,
which is attached by one edge to the abdominal wall from the lower border of the kidney to the iliac fossa and by the other
to the postero-lateral aspect of the colon. In some instances additional fossae, the retrocecal fossae, are present.
3. The intersigmoid fossa (recessus intersigmoideus) is constant in the fetus and during infancy, but disappears in a certain
percentage of cases as age advances. Upon drawing the sigmoid colon upward, the left surface of the sigmoid mesocolon is
exposed, and on it will be seen a funnel-shaped recess of the peritoneum, lying on the external iliac vessels, in the interspace between the Psoas and Iliacus muscles. This is the orifice leading to the intersigmoid fossa, which lies behind the
sigmoid mesocolon, and in front of the parietal peritoneum. The fossa varies in size; in some instances it is a mere dimple,
whereas in others it will admit the whole of the index finger
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples.
Self-taught class 1. Introduction to splanchnology, topography of organs. Body cavities.
The aim: to learn general terms on topography, to learn the structure of body cavities.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, abdominal surgeons etc.
The abdomen is the largest cavity in the body. It is of an oval shape, the extremities of the oval being directed upward and
downward. The upper extremity is formed by the diaphragm which extends as a dome over the abdomen, so that the cavity
extends high into the bony thorax, reaching on the right side, in the mammary line, to the upper border of the fifth rib; on
the left side it falls below this level by about 2.5 cm. The lower extremity is formed by the structures which clothe the inner
surface of the bony pelvis, principally the Levator ani and Coccygeus on either side. These muscles are sometimes termed
the diaphragm of the pelvis. The cavity is wider above than below, and measures more in the vertical than in the transverse
diameter. In order to facilitate description, it is artificially divided into two parts: an upper and larger part, the abdomen
proper; and a lower and smaller part, the pelvis. These two cavities are not separated from each other, but the limit between
them is marked by the superior aperture of the lesser pelvis.
The abdomen proper differs from the other great cavities of the body in being bounded for the most part by muscles and
fasciæ, so that it can vary in capacity and shape according to the condition of the viscera which it contains; but, in addition
to this, the abdomen varies in form and extent with age and sex. In the adult male, with moderate distension of the viscera,
it is oval in shape, but at the same time flattened from before backward. In the adult female, with a fully developed pelvis,
it is ovoid with the narrower pole upward, and in young children it is also ovoid but with the narrower pole downward.
Boundaries. - It is bounded in front and at the sides by the abdominal muscles and the Iliacus muscles; behind by the vertebral column and the Psoas and Quadratus lumborum muscles; above by the diaphragm; below by the plane of the superior
aperture of the lesser pelvis. The muscles forming the boundaries of the cavity are lined upon their inner surfaces by a layer
of fascia.
The abdomen contains the greater part of the digestive tube; some of the accessory organs to digestion, viz., the liver and
pancreas; the spleen, the kidneys, and the suprarenal glands. Most of these structures, as well as the wall of the cavity in
which they are contained, are more or less covered by an extensive and complicated serous membrane, the peritoneum.
The Apertures in the Walls of the Abdomen. - The apertures in the walls of the abdomen, for the transmission of structures to or from it, are, in front, the umbilical (in the fetus), for the transmission of the umbilical vessels, the allantois, and
vitelline duct; above, the vena caval opening, for the transmission of the inferior vena cava, the aortic hiatus, for the passage of the aorta, azygos vein, and thoracic duct, and the esophageal hiatus, for the esophagus and vagi. Below, there are
two apertures on either side: one for the passage of the femoral vessels and lumboinguinal nerve, and the other for the
transmission of the spermatic cord in the male, and the round ligament of the uterus in the female.
Regions. - For convenience of description of the viscera, as well as of reference to the morbid conditions of the contained
parts, the abdomen is artificially divided into nine regions by imaginary planes, two horizontal and two sagittal, passing
through the cavity, the edges of the planes being indicated by lines drawn on the surface of the body. Of the horizontal
planes the upper or transpyloric is indicated by a line encircling the body at the level of a point midway between the jugular
notch and the symphysis pubis, the lower by a line carried around the trunk at the level of a point midway between the
transpyloric and the symphysis pubis.
The middle region of the upper zone is called the epigastric; and the two lateral regions, the right and left hypochondriac.
The central region of the middle zone is the umbilical; and the two lateral regions, the right and left lumbar. The middle
region of the lower zone is the hypogastric or pubic region; and the lateral regions are the right and left iliac or inguinal
The pelvis is that portion of the abdominal cavity which lies below and behind a plane passing through the promontory of
the sacrum, lineæ terminales of the hip bones, and the pubic crests. It is bounded behind by the sacrum, coccyx, Piriformes,
and the sacrospinous and sacrotuberous ligaments; in front and laterally by the pubes and ischia and Obturatores interni;
above it communicates with the abdomen proper; below it is closed by the Levatores ani and Coccygei and the urogenital
diaphragm. The pelvis contains the urinary bladder, the sigmoid colon and rectum, a few coils of the small intestine, and
some of the generative organs.
When the anterior abdominal wall is removed, the viscera are partly exposed as follows: above and to the right side is the
liver, situated chiefly under the shelter of the right ribs and their cartilages, but extending across the middle line and reaching for some distance below the level of the xiphoid process. To the left of the liver is the stomach, from the lower border
of which an apron-like fold of peritoneum, the greater omentum, descends for a varying distance, and obscures, to a greater
or lesser extent, the other viscera. Below it, however, some of the coils of the small intestine can generally be seen, while in
the right and left iliac regions respectively the cecum and the iliac colon are partly exposed. The bladder occupies the anterior part of the pelvis, and, if distended, will project above the symphysis pubis; the rectum lies in the concavity of the sacrum, but is usually obscured by the coils of the small intestine. The sigmoid colon lies between the rectum and the bladder.
When the stomach is followed from left to right it is seen to be continuous with the first part of the small intestine, or duodenum, the point of continuity being marked by a thickened ring which indicates the position of the pyloric valve. The duodenum passes toward the under surface of the liver, and then, curving downward, is lost to sight. If, however, the greater
omentum be thrown upward over the chest, the inferior part of the duodenum will be observed passing across the vertebral
column toward the left side, where it becomes continuous with the coils of the jejunum and ileum. These measure some 6
meters in length, and if followed downward the ileum will be seen to end in the right iliac fossa by opening into the cecum,
the commencement of the large intestine. From the cecum the large intestine takes an arched course, passing at first upward
on the right side, then across the middle line and downward on the left side, and forming respectively the ascending transverse, and descending parts of the colon. In the pelvis it assumes the form of a loop, the sigmoid colon, and ends in the rectum.
The spleen lies behind the stomach in the left hypochondriac region, and may be in part exposed by pulling the stomach
over toward the right side.
The glistening appearance of the deep surface of the abdominal wall and of the surfaces of the exposed viscera is due to
the fact that the former is lined, and the latter are more or less completely covered, by a serous membrane, the peritoneum.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples.
Self-taught class 2. Teeth development, age peculiarities of teeth development.
The aim: to learn the development of teeth, to find out age peculiarities in teeth structure.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially dentists,
therapeutists, pediatritians, obstetricians, forensic medics etc.
Development of the Teeth. In describing the development of the teeth, the mode of formation of the deciduous teeth must
first be considered, and then that of the permanent series.
Development of the Deciduous Teeth. The development of the deciduous teeth begins about the sixth week of fetal life as a
thickening of the epithelium along the line of the future jaw, the thickening being due to a rapid multiplication of the more
deeply situated epithelial cells. As the cells multiply they extend into the subjacent mesoderm, and thus form a ridge or
strand of cells imbedded in mesoderm. About the seventh week a longitudinal splitting or cleavage of this strand of cells
takes place, and it becomes divided into two strands; the separation begins in front and extends laterally, the process occupying four or five weeks. Of the two strands thus formed, the labial forms the labiodental lamina; while the other, the lingual, is the ridge of cells in connection with which the teeth, both deciduous and permanent, are developed. Hence it is
known as the dental lamina or common dental germ. It forms a flat band of cells, which grows into the substance of the
embryonic jaw, at first horizontally inward, and then, as the teeth develop, vertically, i. e., upward in the upper jaw, and
downward in the lower jaw. While still maintaining a horizontal direction it has two edges – an attached edge, continuous
with the epithelium lining the mouth, and a free edge, projecting inward, and imbedded in the mesodermal tissue of the
embryonic jaw. Along its line of attachment to the buccal epithelium is a shallow groove, the dental furrow.
About the ninth week the dental lamina begins to develop enlargements along its free border. These are ten in number in
each jaw, and each corresponds to a future deciduous tooth. They consist of masses of epithelial cells; and the cells of the
deeper part - that is, the part farthest from the margin of the jaw - increase rapidly and spread out in all directions. Each
mass thus comes to assume a club shape, connected with the general epithelial lining of the mouth by a narrow neck, embraced by mesoderm. They are now known as special dental germs. After a time the lower expanded portion inclines outward, so as to form an angle with the superficial constricted portion, which is sometimes known as the neck of the special
dental germ. About the tenth week the mesodermal tissue beneath these special dental germs becomes differentiated into
papillae; these grow upward, and come in contact with the epithelial cells of the special dental germs, which become folded
over them like a hood or cap. There is, then, at this stage a papilla (or papillae) which has already begun to assume somewhat the shape of the crown of the future tooth, and from which the dentin and pulp of the tooth are formed, surmounted by
a dome or cap of epithelial cells from which the enamel is derived.
In the meantime, while these changes have been going on, the dental lamina has been extending backward behind the special dental germ corresponding to the second deciduous molar tooth, and at about the seventeenth week it presents an enlargement, the special dental germ, for the first permanent molar, soon followed by the formation of a papilla in the mesodermal tissue for the same tooth. This is followed, about the sixth month after birth, by a further extension backward of the
dental lamina, with the formation of another enlargement and its corresponding papilla for the second molar. And finally
the process is repeated for the third molar, its papilla appearing about the fifth year of life.
After the formation of the special dental germs, the dental lamina undergoes atrophic changes and becomes cribriform,
except on the lingual and lateral aspects of each of the special germs of the temporary teeth, where it undergoes a local
thickening forming the special dental germ of each of the successional permanent teeth – i. e., the ten anterior ones in each
jaw. Here the same process goes on as has been described in connection with those of the deciduous teeth: that is, they recede into the substance of the gum behind the germs of the deciduous teeth. As they recede they become club-shaped, form
expansions at their distal extremities, and finally meet papillae, which have been formed in the mesoderm, just in the same
manner as was the case in the deciduous teeth. The apex of each papilla indents the dental germ, which encloses it, and,
forming a cap for it, becomes converted into the enamel, while the papilla forms the dentin and pulp of the permanent
tooth.
The special dental germs consist at first of rounded or polyhedral epithelial cells; after the formation of the papillae, these
cells undergo a differentiation into three layers. Those which are in immediate contact with the papilla become elongated,
and form a layer of well-marked columnar epithelium coating the papilla. They are the cells which form the enamel fibers,
and are therefore termed enamel cells or adamantoblasts. The cells of the outer layer of the special dental germ, which are
in contact with the inner surface of the dental sac, presently to be described, are much shorter, cubical in form, and are
named the external enamel epithelium. All the intermediate round cells of the dental germ between these two layers undergo a peculiar change. They become stellate in shape and develop processes, which unite to form a net-work into which fluid
is secreted; this has the appearance of a jelly, and to it the name of enamel pulp is given. This transformed special dental
germ is now known under the name of enamel organ.
While these changes are going on, a sac is formed around each enamel organ from the surrounding mesodermal tissue.
This is known as the dental sac, and is a vascular membrane of connective tissue. It grows up from below, and thus encloses the whole tooth germ; as it grows it causes the neck of the enamel organ to atrophy and disappear; so that all communication between the enamel organ and the superficial epithelium is cut off. At this stage there are vascular papillae surmounted by caps of epithelial cells, the whole being surrounded by by membranous sacs.
Formation of the Alveoli. - About the fourteenth week of embryonic life the dental lamina becomes enclosed in a trough
or groove of mesodermal tissue, which at first is common to all the dental germs, but subsequently becomes divided by
bony septa into loculi, each loculus containing the special dental germ of a deciduous tooth and its corresponding permanent tooth. After birth each cavity becomes subdivided, so as to form separate loculi (the future alveoli) for the deciduous
tooth and its corresponding permanent tooth. Although at one time the whole of the growing tooth is contained in the cavity
of the alveolus, the latter never completely encloses it, since there is always an aperture over the top of the crown filled by
soft tissue, by which the dental sac is connected with the surface of the gum, and which in the permanent teeth is called the
gubernaculum dentis.
Development of the Permanent Teeth – The permanent teeth as regards their development may be divided into two sets: (1)
those which replace the deciduous teeth, and which, like them, are ten in number in each jaw: these are the successional
permanent teeth; and (2) those which have no deciduous predecessors, but are superadded distal to the temporary dental
series. These are three in number on either side in each jaw, and are termed superadded permanent teeth. They are the three
molars of the permanent set, the molars of the deciduous set being replaced by the premolars of the permanent set. The development of the successional permanent teeth – the ten anterior ones in either jaw – has already been indicated. During
their development the permanent teeth, enclosed in their sacs, come to be placed on the lingual side of the deciduous teeth
and more distant from the margin of the future gum, and, as already stated, are separated from them by bony partitions. As
the crown of the permanent tooth grows, absorption of these bony partitions and of the root of the deciduous tooth takes
place, through the agency of osteoclasts, which appear at this time, and finally nothing but the crown of the deciduous tooth
remains. This is shed or removed, and the permanent tooth takes its place.
The superadded permanent teeth are developed in the manner already described, by extensions backward of the posterior
part of the dental lamina in each jaw.
Eruption of the Teeth. When the calcification of the different tissues of the tooth is sufficiently advanced to enable it to bear
the pressure to which it will be afterward subjected, eruption takes place, the tooth making its way through the gum. The
gum is absorbed by the pressure of the crown of the tooth against it, which is itself pressed up by the increasing size of the
root. At the same time the septa between the dental sacs ossify, and constitute the alveoli; these firmly embrace the necks of
the teeth, and afford them a solid basis of support.
The eruption of the deciduous teeth commences about the seventh month after birth, and is completed about the end of the
second year, the teeth of the lower jaw preceding those of the upper.
The following are the most usual times of eruption:
Lower central incisors 6 to 9 months.
Upper incisors 8 to 10 months.
Lower lateral incisors and first molars 15 to 21 months.
Canines 16 to 20 months.
Second molars 20 to 24 months.
Calcification of the permanent teeth proceeds in the following order in the lower jaw (in the upper jaw it takes place a
little later): the first molar, soon after birth; the central and lateral incisors, and the canine, about six months after birth; the
premolars, at the second year, or a little later; the second molar, about the end of the second year; the third molar, about the
twelfth year.
The eruption of the permanent teeth takes place at the following periods, the teeth of the lower jaw preceding those of the
upper by short intervals:
First molars 6th year.
Two central incisors 7th year.
Two lateral incisors 8th year.
First premolars 9th year.
Second premolars 10th year.
Canines 11th to 12th year.
Second molars 12th to 13th year.
Third molars 17th to 25th year.
Toward the sixth year, before the shedding of the deciduous teeth begins, there are twenty-four teeth in each jaw, viz., the
ten deciduous teeth and the crowns of all the permanent teeth except the third molars.
Practice skills
Students are supposed to give the terms of deciduous and permanent teeth eruption, know the order of teeth
eruption.
Self-taught class 3. Development of abdominal organs and peritoneum. Peritoneum: relations,
derivatives, bursas and recesses.
The aim: to learn the development of abdominal viscera, to study the anatomy and topography of peritoneum
and its derivatives.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, abdominal surgeons etc.
The lower foregut begins at the level of the lung buds with the esophagus, followed by the stomach and the superior part of
the duodenum. It extends as far as the liver bud and the pancreas, the bile passages also arise from it. A massive lengthening of the whole intestines in a cranio-caudal growth gradient takes place: in the beginning it is mainly the esophagus and
stomach that lengthen. Thus a shift of these structures relative to the vertebral column occurs. One also speaks of a descent
of the stomach. This lengthening not only leads to a relative relocation with respect to the spine but it also coupled to the
so-called "stomach rotation".
Esophagus
At the level of the last pharyngeal pouch of the embryo the foregut is suddenly very narrow and gives out ventrally the lung
bud. This is the point where the esophagus originates which, in the beginning, is very short. During the lung development
and the descent of the heart it lengthens considerably. The esophagus continues in the spindle-shaped stomach and the duodenum with the ventrally budding liver and the dorsally budding dorsal pancreas anlage.
In the early stages of development the epithelium of the esophagus is composed of multiple rows. At the end of the embryonic period large vacuoles arise in the almost closed lumen. In the early fetal period these merge and the esophagus becomes recanalized. The epithelium is now a multi-layered, prismatic ciliated epithelium. In the middle of the pregnancy is
finally replaced by the definitive, layered squamous epithelium.
The muscle layers of the esophagus arise in the late embryonic period. The lamina muscularis mucosae and the inner layer
of the ring musculature arise subsequently out of cells of the local splanchnopleurae.
The striated muscles of the outer layer of the circular musculature and the outer longitudinal muscles stem from the mesoderm of the last pharyngeal arch.
The entire musculature is innervated by the vagus nerve (cranial nerve X of the 4th pharyngeal arch).
The stomach becomes visible very early in the development as a fusiform enlargement of the intestinal tube.
The stomach is connected with the dorsal body wall through the dorsal mesogastrium, a duplicate of the peritoneum, and
ventrally through the ventral mesogastrium with the transverse septum. The developing liver grows as a ventral budding of
the intestinal tube into the transverse septum. The ventral mesogastrium is thus subdivided into a portion connecting the
stomach to liver (the hepatogastric ligament or omentum minus) and a second portion that ties the liver and abdominal wall
together (the falciform ligament). The coelomic gap in the region of the midgut (peritoneal cavity) extends towards the left
cranially and to the right of the liver and forms the visceral envelope of the liver.
The stomach is shifted to the left and turns 90 degrees, the right wall lying dorsally. This results, though, more from a substantial growth of the left wall (later anterior wall) of the stomach and of the fundus than from an active rotation. The relatively short connective tissue bridge of the stomach to the posterior body wall stretches into a long, extended fold, the dorsal mesogastrium. Later the dorsal pancreas and the spleen anlage grow into it. Essential that the differing spurts of growth
in the various stomach sections not only lead to shape but also to positional changes is the fact that the duodenum is fixed
onto the posterior abdominal wall quite early. From its original intraperitoneal location it assumes a secondary retroperitoneal position. The duodenum is thus a component of the vessel-pancreas-stalk. The caudal shifting of the entire foregut
mentioned at the beginning comes to an end with the formation of the diaphragm and the resulting fixation of the esophagus-cardia passage as well as the formation of the vessel-pancreas-stalk at the level of the duodenum. With this fixation of
the stomach at the cardia and pylorus the spurts of growth in the stomach wall now lead only to a horizontal movement of
the organ to the left with the above mentioned turn of 90 degrees.
Duodenum
As a whole, the duodenum loop lies to the right on the abdominal wall. Its peritoneal layers stick and fuse to the peritoneal
layer that lines the abdominal cavity parietally. The duodenum thus becomes "secondarily retroperitoneal". The transition
between the foregut and midgut are found on the vertex of the duodenal loop, there where the liver and pancreas anlagen
arise. Probably no rotation of the duodenal loop occurs, rather it takes on its C-shape due to the extension of the stomach
towards the left and the simultaneous relative fixation by the emerging liver and pancreas anlagen. This results in the inferior horizontal portion of the duodenum being shifted under the superior mesenteric artery..
The midgut extends from the apex of the duodenal loop, which is fixed to the large liver anlage via the bile duct, to the last
third of the transverse colon.
Its parts are:
Inferior part of the duodenum with the duodeno-jejunal bend
Jejunum
Ileum with the iliocaecal valve
Cecum with vermiform appendix
Ascending colon
Transverse colon (2/3)
The midgut is supplied with blood by the superior mesenteric artery and innervated by the vagus nerve (CN X). Within the
whole midgut and rectum unit there exists only one dorsal mesenterium, the ventral being readsorbed. Differentiation occurs in a cranio caudal sequence within a time window of roughly one week.
The midgut begins to extend into the umbilical coelom and forms the umbilical loop, whereby initially from the apex only a
wide connection to the umbilical vesicle exists. In the further development this junction becomes constricted to become the
omphalomesenteric duct. Mostly it is later obliterated, but can also partially remain as a Meckel's diverticulum. In the beginning the umbilical loop is positioned sagittally.
The intestinal tube becomes enwrapped by the visceral peritoneum that connects it to the posterior body wall forming the
dorsal mesenterium. In this stage the intestinal tube is almost straight and is connected to the umbilical vesicle by the omphalo-mesenteric duct.
Only when the umbilical loop lengthens and grows into the umbilical coelom does it experience a rotation of 90 degrees in
a clockwise direction as seen from the embryo. The cranial pedicle comes to lie to the right and the caudal to the left. The
umbilical loop now has a horizontal position. Through the cranio-caudal growth gradient, the cranial pedicle forms first
through lengthening of several loops in the umbilical coelom.
The developing umbilical loop extends further into the umbilical coelom because there is no more room for it within the
embryo's abdominal cavity. It is the time of the strongest flexion of the embryo. Very soon a thickening in the region of the
caudal pedicle of the intestinal tube is also to be seen: the cecum. Visually, it becomes an important fixed point for purposes of orientation.
The entire intestinal loop has relocated in the umbilical coelom due to the limited space conditions in the abdominal cavity.
The intestinal loop now has a horizontal orientation and the lengthening tube has formed several loops in the cranial pedicle. The caudal part is still straight.
As development proceeds the intestinal loop turns further around its own axis. The extension of the intestinal loop into the
umbilical coelom has reached its maximum. This physiologic navel hernia remains in existence up to the 9th week of pregnancy. (Omphalocele / umbilical hernia)
The largest part of the intestinal loop lies in the umbilical coelom and several loops have formed through the lengthening in
the cranial, small intestine region.
At first, the loops of the small intestine return into the abdominal cavity and come to lie in the left half surrounded by the
horizontal and descending part of the colon that never left the abdominal cavity. The rotation now amounts to more than
180 degrees and the colon is also shifted more and more into the abdominal space. The repositioning of the physiologic
umbilical hernia is facilitated by the righting of the embryo's body.
With the return of the intestines into the abdominal cavity the small intestine is moved to the left side and the cecum and
the ascending part of the large intestine to the right. Initially the cecum may possibly be found in the upper right quadrant
(elevated cecum).
Thus, after the reintegration of the intestinal loops into the abdominal cavity from the physiologic umbilical hernia, the
derivatives of the originally caudal pedicle occupies the upper and ventral part of the abdominal cavity. At the end of the
embryonic period this part migrates downwards into the iliac fossa, whereby an additional rotation occurs. The whole rotation of the intestines thus amounts to approximately 270 degrees. As a consequence, the mesenterium also turns with it and
in its insertion it crosses over the inferior part of the duodenum. (Malrotation and congenital high cecum)
The hindgut extends from the left third of the transverse colon to the cloaca (rectum). In contrast to the midgut, no intestinal rotation occurs here but rather this part gets pushed to the left side by the midgut returning from the umbilical coelom.
It consists of:
Transverse colon (left third)
Descending colon
Sigmoid colon
Rectum
Anal canal
Hindgut
Initially the hindgut dead-ends in the cloaca and is separated by the cloacal membrane from the ectodermal anal pit, the
proctodaeum. In addition, at its end, it is connected to the allantois and to the mesonephric duct.
The cloaca flattens in the frontal plane and extends somewhat in the sagittal plane, whereby from the upper rear and from
both sides a mesenchymal condensation, the urorectal septum, arises in the angle between the allantois and the hindgut.
Through this mechanism, the cloaca is subdivided into the urogenital sinus (ventrally) and the anorectal canal (dorsally)
The urorectal septum extends itself caudally (in the direction of the arrow) and subdivides the urorectal sinus into a urogenital sinus and an anorectal canal.
In the cloacal region the urorectal septum thickens still more and forms the material for the deep perineum. The cloacal
membrane ruptures and the endodermal part of the anal canal goes over into the ectodermal part of the proctodeum. During
this period the anorectal canal is closed by an epithelial plug and is recanalized again only in the early fetal period.
The first villi and Lieberkühn's glands arise in the early fetal period. However, they disappear shortly before birth and appear again only after birth. With the beginning of the second trimester the meconium in the large intestine is formed. It consists of dark green material that mainly consists of a mixture of secretions of the intestinal glands and the gall bladder as
well as of amniotic fluid, which is swallowed by the fetus. The intestinal content is sterile up to birth. Following birth the
meconium is passed as the first stool by the newborn.
The mesenteries fixate the intestinal tube to the posterior wall of the abdominal cavity. The blood vessels and nerves utilize
the mesenteries to reach the viscera. Since portions of the mesenteries partially adhere again to the posterior abdominal
wall, the vessels and nerves that course through them also lie secondarily retroperitoneally.
In the region of the stomach and small intestine up to the liver bud exists a ventral fixation, the ventral mesogastrium all the
way to the liver. Therein courses later the portal vein, the hepatic artery and the bile duct. A dorsal "meso" fixates the viscera here to the dorsal abdominal wall.
To the right of the intestinal tube in the region between the esophagus and lungs a niche arises, the recessus pneumatoentericus, that extends down into the peritoneal cavity. With the spreading of the diaphragm it becomes subdivided into a
supra-diaphragmatic cavity, the subcardiac bursa, and an infra-diaphragmatic cavity, the omental bursa. On the left a similar niche arises that, however, soon atrophies or is suppressed by the rotation of the stomach.
With the rotation of the stomach the omental bursa spreads further out and delimits a space behind the stomach with a
small opening into the peritoneal cavity, the epiploic foramen. In the front it is bounded by the ventral mesogastrium or
omentum minus. With the further development the dorsal mesogastrium extends over the large curvature of the stomach in
the caudal direction and forms a mesenterial fold: the greater omentum, which in effect is nothing more than an extended
omental bursa. With time the two layers of the greater omentum , adhere together and further fuse with the transverse mesocolon.
In the region of the small intestine the mesenterial relationships are somewhat more complicated due to the intestinal rotation. The mesenterium of the entire small intestine appears to originate at a point that lies above the inferior part of the du-
odenum. At the level of the large intestine, the mesenterium of the ascending and descending colon becomes positioned on
the posterior abdominal wall, adheres to it, and these two parts become secondary retroperitoneal in the fetal period. The
root of the mesentery rises and runs transversely over the posterior abdominal wall from the cecum to the duodeno-jejunal
bend and corresponds to the attachment of the part of the mesentery of the ascending colon that is fused with the posterior
abdominal wall. Only in the region of the sigmoid flexure does the adhesion not occur and this part remains intraperitoneal
with a mesosigmoid. The rectum is located dorsal and caudal to the peritoneal cavity and thus retroperitoneal.
The pancreas arises from two anlagen, both buddings of the endoderm at the level of the duodenal loop. Initially the dorsal
pancreas grows on the dorsal side of the duodenum into the mesoduodenum.
Somewhat later the ventral pancreas appears as an evagination of the bile duct.
The dorsal pancreas anlage expands relatively rapidly into the mesoduodenum below the large curvature of the stomach. It
comes to lie with its tail-like part (cauda) near the spleen. Its outflow passage, which emerges from its head, normally fuses
with the outflow passage of the ventral pancreas anlage to become the major pancreatic duct. These join with the bile duct
and discharge into the major duodenal papilla. Sometimes the outflow passage of the dorsal pancreas anlage persists as an
independent minor pancreatic duct and discharges somewhat more cranially at the minor duodenal papilla into the duodenum.
Ventral pancreas
The ventral pancreas anlage arises somewhat later as a budding from the bile duct. Due to the 90 degree rotation of the
stomach and the lengthening of the duodenal loop the bile duct with the gall bladder and the ventral pancreas are moved
towards the rear, thus rotating around the duodenum and reaches then a position ventral to the dorsal pancreas. In the adult
pancreas the anterior part of the head (caput), the body (corpus) and the tail (cauda) thus stem from the dorsal part while the
posterior part of the head as well as the uncinate process come from the ventral part.
The position of the orifice of the bile duct and that of the pancreas can vary considerably in adults. Usually the dorsal pancreatic duct opens into the ventral and this ends besides the bile duct at the major duodenal papilla into the duodenum.
Already in a young embryo is the liver recognizable as an epithelial budding of the endoderm at the transition from the intra- to extraembryonic part of the umbilical vesicle below the cardiac anlage.
From the distal part of this originally endodermal sprout arises the actual liver, the middle bud forms the gall bladder with
its passage and from the caudal bud arises the ventral anlage of the pancreas.
Liver development is not simply a sprouting of liver cells into the transverse septum. Instead, complex interactions between the mesoderm and the epithelial cells of the endoderm take place. It is only with the formation of the vessel system
and the development of the portal vein that the definitive organ structure is assembled.
Recent studies on mouse embryos have shown that embryonic hepatocytes stem from endodermal cells that, without induction by mesodermal cells of the transverse septum, normally develop into pancreas cells. This determination to liver cells is
achieved mainly through two signalling factors: FGF (fibroblast growth factor) and BMP (bone morphogenic protein) released by the mesodermal cells of the transverse septum.
The embryonic liver cells (pars hepatica) form themselves into acini and cords that grow into the capillary network that has
arisen in the transverse septum between the two omphalomesenteric veins. Below it arises the gall bladder diverticulum
(pars cystica), which also grows into the transverse septum.
The complex pattern of parenchyma and sinusoids arise in that sheets composed of liver cells are engendered from the cell
cords and the capillares expand to become sinusoids. The hepatic laminas are 5-7 cells thick. This organization is still retained until several years after birth. Until after birth no multi-nuclear hepatocytes are found.
Practice skills
Students are supposed to name the parts and derivatives of peritoneum and show them on samples and cadavers.
UNIT 8. RESPRATORY SYSTEM
Practice class 8. Written tests and examination of practice skills on digestive system. Examination of self-taught tasks. Review of respiratory system. External nose.
Practice class 9. Nasal cavity: walls, paranasal sinuses, meatuses, communications. Pharynx.
Practice class 10. Larynx: relations, cartilages, muscles, joints.
The aim: to learn the anatomy of larynx, its relations, cartilages, muscles, joints; to understand the principles of movements in the joints of larynx.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, otorhinolaringologists, anaestesiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The larynx or organ of voice is placed at the upper part of the air passage. It is situated between the trachea and the root of
the tongue, at the upper and forepart of the neck, where it presents a considerable projection in the middle line. It forms the
lower part of the anterior wall of the pharynx, and is covered behind by the mucous lining of that cavity; on either side of it
lie the great vessels of the neck. Its vertical extent corresponds to the fourth, fifth, and sixth cervical vertebrae, but it is
placed somewhat higher in the female and also during childhood. Symington found that in infants between six and twelve
months of age the tip of the epiglottis was a little above the level of the fibrocartilage between the odontoid process and
body of the axis, and that between infancy and adult life the larynx descends for a distance equal to two vertebral bodies
and two intervertebral fibrocartilages. According to Sappey the average measurements of the adult larynx are as follows:
In males.
In females.
Length
44 mm.
36 mm.
Transverse diameter
43 mm.
41 mm.
Antero-posterior diameter
36 mm.
26 mm.
Circumference
136 mm.
112 mm.
Until puberty the larynx of the male differs little in size from that of the female. In the female its increase after puberty is
only slight; in the male it undergoes considerable increase; all the cartilages are enlarged and the thyroid cartilage becomes
prominent in the middle line of the neck, while the length of the rima glottidis is nearly doubled.
The larynx is broad above, where it presents the form of a triangular box flattened behind and at the sides, and bounded in
front by a prominent vertical ridge. Below, it is narrow and cylindrical. It is composed of cartilages, which are connected
together by ligaments and moved by numerous muscles. It is lined by mucous membrane continuous above with that of the
pharynx and below with that of the trachea.
The Cartilages of the Larynx (cartilagines laryngis) are nine in number, three single and three paired, as follows:
Thyroid.
Two Corniculate.
Cricoid.
Two Cuneiform.
Two Arytenoid.
Epiglottis.
The Thyroid Cartilage (cartilago thyreoidea) is the largest cartilage of the larynx. It consists of two laminae the anterior
borders of which are fused with each other at an acute angle in the middle line of the neck, and form a subcutaneous projection named the laryngeal prominence (pomum Adami). This prominence is most distinct at its upper part, and is larger in
the male than in the female. Immediately above it the laminae are separated by a V-shaped notch, the superior thyroid
notch. The laminae are irregularly quadrilateral in shape, and their posterior angles are prolonged into processes termed the
superior and inferior cornua.
The outer surface of each lamina presents an oblique line which runs downward and forward from the superior thyroid
tubercle situated near the root of the superior cornu, to the inferior thyroid tubercle on the lower border. This line gives
attachment to the Sternothyreoideus, Thyreohyoideus, and Constrictor pharyngis inferior.
The inner surface is smooth; above and behind, it is slightly concave and covered by mucous membrane. In front, in the
angle formed by the junction of the laminae, are attached the stem of the epiglottis, the ventricular and vocal ligaments, the
Thyreoarytaenoidei, Thyreoepiglottici and Vocales muscles, and the thyroepiglottic ligament.
The upper border is concave behind and convex in front; it gives attachment to the corresponding half of the hyothyroid
membrane.
The lower border is concave behind, and nearly straight in front, the two parts being separated by the inferior thyroid tubercle. A small part of it in and near the middle line is connected to the cricoid cartilage by the middle cricothyroid ligament.
The posterior border, thick and rounded, receives the insertions of the Stylopharyngeus and Pharyngopalatinus. It ends
above, in the superior cornu, and below, in the inferior cornu. The superior cornu is long and narrow, directed upward,
backward, and medialward, and ends in a conical extremity, which gives attachment to the lateral hyothyroid ligament. The
inferior cornu is short and thick; it is directed downward, with a slight inclination forward and medialward, and presents, on
the medial side of its tip, a small oval articular facet for articulation with the side of the cricoid cartilage.
During infancy the laminae of the thyroid cartilage are joined to each other by a narrow, lozenge-shaped strip, named the
intrathyroid cartilage. This strip extends from the upper to the lower border of the cartilage in the middle line, and is distinguished from the laminae by being more transparent and more flexible.
The Cricoid Cartilage (cartilago cricoidea) is smaller, but thicker and stronger than the thyroid, and forms the lower and
posterior parts of the wall of the larynx. It consists of two parts: a posterior quadrate lamina, and a narrow anterior arch,
one-fourth or one-fifth of the depth of the lamina.
The lamina (lamina cartilaginis cricoideae; posterior portion) is deep and broad, and measures from above downward
about 2 or 3 cm.; on its posterior surface, in the middle line, is a vertical ridge to the lower part of which are attached the
longitudinal fibers of the esophagus; and on either side of this a broad depression for the Cricoarytaenoideus posterior.
The arch (arcus cartilaginis cricoideae; anterior portion) is narrow and convex, and measures vertically from 5 to 7 mm.; it
affords attachment externally in front and at the sides to the Cricothyreiodei, and behind, to part of the Constrictor pharyngis inferior.
On either side, at the junction of the lamina with the arch, is a small round articular surface, for articulation with the inferior cornu of the thyroid cartilage.
The lower border of the cricoid cartilage is horizontal, and connected to the highest ring of the trachea by the cricotracheal
ligament.
The upper border runs obliquely upward and backward, owing to the great depth of the lamina. It gives attachment, in
front, to the middle cricothyroid ligament; at the side, to the conus elasticus and the Cricoarytaenoidei laterales; behind, it
presents, in the middle, a shallow notch, and on either side of this is a smooth, oval, convex surface, directed upward and
lateralward, for articulation with the base of an arytenoid cartilage.
The inner surface of the cricoid cartilage is smooth, and lined by mucous membrane.
The Arytenoid Cartilages (cartilagines arytaenoideae) are two in number, and situated at the upper border of the lamina of
the cricoid cartilage, at the back of the larynx. Each is pyramidal in form, and has three surfaces, a base, and an apex.
The posterior surface is a triangular, smooth, concave, and gives attachment to the Arytaenoidei obliquus and transversus.
The antero-lateral surface is somewhat convex and rough. On it, near the apex of the cartilage, is a rounded elevation (colliculus) from which a ridge (crista arcuata) curves at first backward and then downward and forward to the vocal process.
The lower part of this crest intervenes between two depressions or foveae, an upper, triangular, and a lower oblong in
shape; the latter gives attachment to the Vocalis muscle.
The medial surface is narrow, smooth, and flattened, covered by mucous membrane, and forms the lateral boundary of the
intercartilaginous part of the rima glottidis.
The base of each cartilage is broad, and on it is a concave smooth surface, for articulation with the cricoid cartilage. Its
lateral angle is short, rounded, and prominent; it projects backward and lateralward, and is termed the muscular process; it
gives insertion to the Cricoarytaenoideus posterior behind, and to the Cricoarytaenoideus lateralis in front. Its anterior angle, also prominent, but more pointed, projects horizontally forward; it gives attachment to the vocal ligament, and is called
the vocal process.
The apex of each cartilage is pointed, curved backward and medialward, and surmounted by a small conical, cartilaginous
nodule, the corniculate cartilage.
The Corniculate Cartilages (cartilagines corniculatae; cartilages of Santorini) are two small conical nodules consisting of
yellow elastic cartilage, which articulate with the summits of the arytenoid cartilages and serve to prolong them backward
and medialward. They are situated in the posterior parts of the aryepiglottic folds of mucous membrane, and are sometimes
fused with the arytenoid cartilages.
The Cuneiform Cartilages (cartilagines cuneiformes; cartilages of Wrisberg) are two small, elongated pieces of yellow
elastic cartilage, placed one on either side, in the aryepiglottic fold, where they give rise to small whitish elevations on the
surface of the mucous membrane, just in front of the arytenoid cartilages.
The Epiglottis (cartilago epiglottica) is a thin lamella of fibrocartilage of a yellowish color, shaped like a leaf, and projecting obliquely upward behind the root of the tongue, in front of the entrance to the larynx. The free extremity is broad and
rounded; the attached part or stem is long, narrow, and connected by the thyroepiglottic ligament to the angle formed by the
two laminae of the thyroid cartilage, a short distance below the superior thyroid notch. The lower part of its anterior surface
is connected to the upper border of the body of the hyoid bone by an elastic ligamentous band, the hyoepiglottic ligament.
The anterior or lingual surface is curved forward, and covered on its upper, free part by mucous membrane which is reflected on to the sides and root of the tongue, forming a median and two lateral glossoepiglottic folds; the lateral folds are
partly attached to the wall of the pharynx. The depressions between the epiglottis and the root of the tongue, on either side
of the median fold, are named the valleculae. The lower part of the anterior surface lies behind the hyoid bone, the hyothyroid membrane, and upper part of the thyroid cartilage, but is separated from these structures by a mass of fatty tissue.
The posterior or laryngeal surface is smooth, concave from side to side, concavo-convex from above downward; its lower
part projects backward as an elevation, the tubercle or cushion. When the mucous membrane is removed, the surface of the
cartilage is seen to be indented by a number of small pits, in which mucous glands are lodged. To its sides the aryepiglottic
folds are attached.
Structure. - The corniculate and cuneiform cartilages, the epiglottis, and the apices of the arytenoids at first consist of
hyaline cartilage, but later elastic fibers are deposited in the matrix, converting them into yellow fibrocartilage, which
shows little tendency to calcification. The thyroid, cricoid, and the greater part of the arytenoids consist of hyaline cartilage,
and become more or less ossified as age advances. Ossification commences about the twenty-fifth year in the thyroid cartilage, and somewhat later in the cricoid and arytenoids; by the sixty-fifth year these cartilages may be completely converted
into bone.
Ligaments - The ligaments of the larynx are extrinsic, i. e., those connecting the thyroid cartilage and epiglottis with the
hyoid bone, and the cricoid cartilage with the trachea; and intrinsic, those which connect the several cartilages of the larynx
to each other.
Extrinsic Ligaments. - The ligaments connecting the thyroid cartilage with the hyoid bone are the hyothyroid membrane,
and a middle and two lateral hyothyroid ligaments.
The Hyothyroid Membrane (membrana hyothyreoidea; thyrohyoid membrane) is a broad, fibro-elastic layer, attached below to the upper border of the thyroid cartilage and to the front of its superior cornu, and above to the upper margin of the
posterior surface of the body and greater cornua of the hyoid bone, thus passing behind the posterior surface of the body of
the hyoid, and being separated from it by a mucous bursa, which facilitates the upward movement of the larynx during deglutition. Its middle thicker part is termed the middle hyothyroid ligament (ligamentum hyothyreoideum medium; middle
thyrohyoid ligament), its lateral thinner portions are pierced by the superior laryngeal vessels and the internal branch of the
superior laryngeal nerve. Its anterior surface is in relation with the Thyreohyoideus, Sternohyoideus, and Omohyoideus,
and with the body of the hyoid bone.
The Lateral Hyothyroid Ligament (ligamentum hyothyreoideum laterale; lateral thyrohyoid ligament) is a round elastic
cord, which forms the posterior border of the hyothyroid membrane and passes between the tip of the superior cornu of the
thyroid cartilage and the extremity of the greater cornu of the hyoid bone. A small cartilaginous nodule (cartilago triticea),
sometimes bony, is frequently found in it.
The Epiglottis is connected with the hyoid bone by an elastic band, the hyoepiglottic ligament (ligamentum hyoepiglotticum), which extends from the anterior surface of the epiglottis to the upper border of the body of the hyoid bone. The glossoepiglottic folds of mucous membrane may also be considered as extrinsic ligaments of the epiglottis.
The Cricotracheal Ligament (ligamentum cricotracheale) connects the cricoid cartilage with the first ring of the trachea. It
resembles the fibrous membrane which connects the cartilaginous rings of the trachea to each other.
Intrinsic Ligaments. - Beneath the mucous membrane of the larynx is a broad sheet of fibrous tissue containing many
elastic fibers, and termed the elastic membrane of the larynx. It is subdivided on either side by the interval between the ventricular and vocal ligaments, the upper portion extends between the arytenoid cartilage and the epiglottis and is often poorly
defined; the lower part is a well-marked membrane forming, with its fellow of the opposite side, the conus elasticus which
connects the thyroid, cricoid, and arytenoid cartilages to one another. In addition the joints between the individual cartilages are provided with ligaments.
The Conus Elasticus (cricothyroid membrane) is composed mainly of yellow elastic tissue. It consists of an anterior and
two lateral portions. The anterior part or middle cricothyroid ligament (ligamentum cricothyreoideum medium; central part
of cricothyroid membrane) is thick and strong, narrow above and broad below. It connects together the front parts of the
contiguous margins of the thyroid and cricoid cartilages. It is overlapped on either side by the Cricothyreoideus, but between these is subcutaneous; it is crossed horizontally by a small anastomotic arterial arch, formed by the junction of the
two cricothyroid arteries, branches of which pierce it. The lateral portions are thinner and lie close under the mucous membrane of the larynx; they extend from the superior border of the cricoid cartilage to the inferior margin of the vocal ligaments, with which they are continuous. These ligaments may therefore be regarded as the free borders of the lateral portions of the conus elasticus, and extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage about midway between its upper and lower borders.
An articular capsule, strengthened posteriorly by a well-marked fibrous band, encloses the articulation of the inferior cornu of the thyroid with the cricoid cartilage on either side.
Each arytenoid cartilage is connected to the cricoid by a capsule and a posterior cricoarytenoid ligament. The capsule
(capsula articularis cricoarytenoidea) is thin and loose, and is attached to the margins of the articular surfaces. The posterior
cricoarytenoid ligament (ligamentum cricoarytenoideum posterius) extends from the cricoid to the medial and back part of
the base of the arytenoid.
The thyroepiglottic ligament (ligamentum thyreoepiglotticum) is a long, slender, elastic cord which connects the stem of
the epiglottis with the angle of the thyroid cartilage, immediately beneath the superior thyroid notch, above the attachment
of the ventricular ligaments.
Movements. - The articulation between the inferior cornu of the thyroid cartilage and the cricoid cartilage on either side is
a diarthrodial one, and permits of rotatory and gliding movements. The rotatory movement is one in which the cricoid cartilage rotates upon the inferior cornua of the thyroid cartilage around an axis passing transversely through both joints. The
gliding movement consists in a limited shifting of the cricoid on the thyroid in different directions.
The articulation between the arytenoid cartilages and the cricoid is also a diarthrodial one, and permits of two varieties of
movement: one is a rotation of the arytenoid on a vertical axis, whereby the vocal process is moved lateralward or medialward, and the rima glottidis increased or diminished; the other is a gliding movement, and allows the arytenoid cartilages to
approach or recede from each other; from the direction and slope of the articular surfaces lateral gliding is accompanied by
a forward and downward movement. The two movements of gliding and rotation are associated, the medial gliding being
connected with medialward rotation, and the lateral gliding with lateralward rotation. The posterior cricoarytenoid ligaments limit the forward movement of the arytenoid cartilages on the cricoid.
Interior of the Larynx - The cavity of the larynx (cavum laryngis) extends from the laryngeal entrance to the lower border
of the cricoid cartilage where it is continuous with that of the trachea. It is divided into two parts by the projection of the
vocal folds, between which is a narrow triangular fissure or chink, the rima glottidis. The portion of the cavity of the larynx
above the vocal folds is called the vestibule; it is wide and triangular in shape, its base or anterior wall presenting, however,
about its center the backward projection of the tubercle of the epiglottis. It contains the ventricular folds, and between these
and the vocal folds are the ventricles of the larynx. The portion below the vocal folds is at first of an elliptical form, but
lower down it widens out, assumes a circular form, and is continuous with the tube of the trachea.
The entrance of the larynx is a triangular opening, wide in front, narrow behind, and sloping obliquely downward and
backward. It is bounded, in front, by the epiglottis; behind, by the apices of the arytenoid cartilages, the corniculate cartilages, and the interarytenoid notch; and on either side, by a fold of mucous membrane, enclosing ligamentous and muscular
fibers, stretched between the side of the epiglottis and the apex of the arytenoid cartilage; this is the aryepiglottic fold, on
the posterior part of the margin of which the cuneiform cartilage forms a more or less distinct whitish prominence, the cuneiform tubercle.
The Ventricular Folds (plicœ ventriculares; superior or false vocal cords) are two thick folds of mucous membrane, each
enclosing a narrow band of fibrous tissue, the ventricular ligament which is attached in front to the angle of the thyroid cartilage immediately below the attachment of the epiglottis, and behind to the antero-lateral surface of the arytenoid cartilage,
a short distance above the vocal process. The lower border of this ligament, enclosed in mucous membrane, forms a free
crescentic margin, which constitutes the upper boundary of the ventricle of the larynx.
The Vocal Folds (plicœ vocales; inferior or true vocal cords) are concerned in the production of sound, and enclose two
strong bands, named the vocal ligaments (ligamenta vocales; inferior thyroarytenoid). Each ligament consists of a band of
yellow elastic tissue, attached in front to the angle of the thyroid cartilage, and behind to the vocal process of the arytenoid.
Its lower border is continuous with the thin lateral part of the conus elasticus. Its upper border forms the lower boundary of
the ventricle of the larynx. Laterally, the Vocalis muscle lies parallel with it. It is covered medially by mucous membrane,
which is extremely thin and closely adherent to its surface.
The Ventricle of the Larynx (ventriculus laryngis [Morgagnii]; laryngeal sinus) is a fusiform fossa, situated between the
ventricular and vocal folds on either side, and extending nearly their entire length. The fossa is bounded, above, by the free
crescentic edge of the ventricular fold; below, by the straight margin of the vocal fold; laterally, by the mucous membrane
covering the corresponding Thyreoarytaenoideus. The anterior part of the ventricle leads up by a narrow opening into a
cecal pouch of mucous membrane of variable size called the appendix.
The appendix of the laryngeal ventricle (appendix ventriculi laryngis; laryngeal saccule) is a membranous sac, placed between the ventricular fold and the inner surface of the thyroid cartilage, occasionally extending as far as its upper border or
even higher; it is conical in form, and curved slightly backward. On the surface of its mucous membrane are the openings
of sixty or seventy mucous glands, which are lodged in the submucous areolar tissue. This sac is enclosed in a fibrous capsule, continuous below with the ventricular ligament. Its medial surface is covered by a few delicate muscular fasciculi,
which arise from the apex of the arytenoid cartilage and become lost in the aryepiglottic fold of mucous membrane; laterally it is separated from the thyroid cartilage by the Thyreoepiglotticus. These muscles compress the sac, and express the
secretion it contains upon the vocal folds to lubricate their surfaces.
The Rima Glottidis is the elongated fissure or chink between the vocal folds in front, and the bases and vocal processes
of the arytenoid cartilages behind. It is therefore subdivided into a larger anterior intramembranous part (glottis vocalis),
which measures about three-fifths of the length of the entire aperture, and a posterior intercartilaginous part (glottis respiratoria). Posteriorly it is limited by the mucous membrane passing between the arytenoid cartilages. The rima glottidis is the
narrowest part of the cavity of the larynx, and its level corresponds with the bases of the arytenoid cartilages. Its length, in
the male, is about 23 mm.; in the female from 17 to 18 mm. The width and shape of the rima glottidis vary with the movements of the vocal folds and arytenoid cartilages during respiration and phonation. In the condition of rest, i. e., when these
structures are uninfluenced by muscular action, as in quiet respiration, the intramembranous part is triangular, with its apex
in front and its base behind - the latter being represented by a line, about 8 mm. long, connecting the anterior ends of the
vocal processes, while the medial surfaces of the arytenoids are parallel to each other, and hence the intercartilaginous part
is rectangular. During extreme adduction of the vocal folds, as in the emission of a high note, the intramembranous part is
reduced to a linear slit by the apposition of the vocal folds, while the intercartilaginous part is triangular, its apex corresponding to the anterior ends of the vocal processes of the arytenoids, which are approximated by the medial rotation of the
cartilages. Conversely in extreme abduction of the vocal folds, as in forced inspiration, the arytenoids and their vocal processes are rotated lateralward, and the intercartilaginous part is triangular in shape but with its apex directed backward. In
this condition the entire glottis is somewhat lozenge-shaped, the sides of the intramembranous part diverging from before
backward, those of the intercartilaginous part diverging from behind forward - the widest part of the aperture corresponding
with the attachments of the vocal folds to the vocal processes.
Muscles. - The muscles of the larynx are extrinsic, passing between the larynx and parts around - these have been described
in the section on Myology; and intrinsic, confined entirely to the larynx.
The intrinsic muscles are:
Cricothyreoideus. Cricoarytaenoideus lateralis. Cricoarytaenoideus posterior. Arytaenoideus. Thyroarytaenoideus.
The Cricothyreoideus (Cricothyroid), triangular in form, arises from the front and lateral part of the cricoid cartilage; its
fibers diverge, and are arranged in two groups. The lower fibers constitute a pars obliqua and slant backward and lateralward to the anterior border of the inferior cornu; the anterior fibers, forming a pars recta, run upward, backward, and lateralward to the posterior part of the lower border of the lamina of the thyroid cartilage.
The medial borders of the two muscles are separated by a triangular interval, occupied by the middle cricothyroid ligament.
The Cricoarytaenoideus posterior (posterior cricoarytenoid) arises from the broad depression on the corresponding half of
the posterior surface of the lamina of the cricoid cartilage; its fibers run upward and lateralward, and converge to be inserted into the back of the muscular process of the arytenoid cartilage. The uppermost fibers are nearly horizontal, the middle
oblique, and the lowest almost vertical.
The Cricoarytaenoideus lateralis (lateral cricoarytenoid) is smaller than the preceding, and of an oblong form. It arises
from the upper border of the arch of the cricoid cartilage, and, passing obliquely upward and backward, is inserted into the
front of the muscular process of the arytenoid cartilage.
The Arytaenoideus is a single muscle, filling up the posterior concave surfaces of the arytenoid cartilages. It arises from
the posterior surface and lateral border of one arytenoid cartilage, and is inserted into the corresponding parts of the opposite cartilage. It consists of oblique and transverse parts. The Arytaenoideus obliquus, the more superficial, forms two fasciculi, which pass from the base of one cartilage to the apex of the opposite one, and therefore cross each other like the
limbs of the letter X; a few fibers are continued around the lateral margin of the cartilage, and are prolonged into the aryepiglottic fold; they are sometimes described as a separate muscle, the Aryepiglotticus. The Arytaenoideus transversus crosses transversely between the two cartilages.
The Thyreoarytaenoideus (Thyroarytenoid) is a broad, thin, muscle which lies parallel with and lateral to the vocal fold,
and supports the wall of the ventricle and its appendix. It arises in front from the lower half of the angle of the thyroid cartilage, and from the middle cricothyroid ligament. Its fibers pass backward and lateralward, to be inserted into the base and
anterior surface of the arytenoid cartilage. The lower and deeper fibers of the muscle can be differentiated as a triangular
band which is inserted into the vocal process of the arytenoid cartilage, and into the adjacent portion of its anterior surface;
it is termed the Vocalis, and lies parallel with the vocal ligament, to which it is adherent.
A considerable number of the fibers of the Thyreoarytaenoideus are prolonged into the aryepiglottic fold, where some of
them become lost, while others are continued to the margin of the epiglottis. They have received a distinctive name, Thyreoepiglotticus, and are sometimes described as a separate muscle. A few fibers extend along the wall of the ventricle from
the lateral wall of the arytenoid cartilage to the side of the epiglottis and constitute the Ventricularis muscle.
Actions. - In considering the actions of the muscles of the larynx, they may be conveniently divided into two groups, vix.:
1. Those which open and close the glottis. 2. Those which regulate the degree of tension of the vocal folds.
The Cricoarytœnoidei posteriores separate the vocal folds, and, consequently, open the glottis, by rotating the arytenoid
cartilages outward around a vertical axis passing through the cricoarytenoid joints; so that their vocal processes and the
vocal folds attached to them become widely separated.
The Cricoarytœnoidei laterales close the glottis by rotating the arytenoid cartilages inward, so as to approximate their vocal processes.
The Arytœnoideus approximates the arytenoid cartilages, and thus closes the opening of the glottis, especially at its back
part.
The Cricothyreoidei produce tension and elongation of the vocal folds by drawing up the arch of the cricoid cartilage and
tilting back the upper border of its lamina; the distance between the vocal processes and the angle of the thyroid is thus increased, and the folds are consequently elongated.
The Thyreoarytœnoidei, consisting of two parts having different attachments and different directions, are rather complicated as regards their action. Their main use is to draw the arytenoid cartilages forward toward the thyroid, and thus shorten
and relax the vocal folds. But, owing to the connection of the deeper portion with the vocal fold, this part, if acting separately, is supposed to modify its elasticity and tension, while the lateral portion rotates the arytenoid cartilage inward, and
thus narrows the rima glottidis by bringing the two vocal folds together.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 11. Trachea. Structure and relations of bronchial tree.
The aim: to learn the anatomy of trachea, its relations; to learn the structure and relations of bronchial tree.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, otorhinolaringologists, pulmonologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The trachea or windpipe is a cartilaginous and membranous tube, extending from the lower part of the larynx, on a level
with the sixth cervical vertebra, to the upper border of the fifth thoracic vertebra, where it divides into the two bronchi, one
for each lung. The trachea is nearly but not quite cylindrical, being flattened posteriorly; it measures about 11 cm. in length;
its diameter, from side to side, is from 2 to 2.5 cm., being always greater in the male than in the female. In the child the
trachea is smaller, more deeply placed, and more movable than in the adult.
Relations. - The anterior surface of the trachea is convex, and covered, in the neck, from above downward, by the isthmus
of the thyroid gland, the inferior thyroid veins, the arteria thyroidea ima (when that vessel exists), the Sternothyreoideus
and Sternohyoideus muscles, the cervical fascia, and, more superficially, by the anastomosing branches between the anterior jugular veins; in the thorax, it is covered from before backward by the manubrium sterni, the remains of the thymus, the
left innominate vein, the aortic arch, the innominate and left common carotid arteries, and the deep cardiac plexus. Posteriorly it is in contact with the esophagus. Laterally, in the neck, it is in relation with the common carotid arteries, the right
and left lobes of the thyroid gland, the inferior thyroid arteries, and the recurrent nerves; in the thorax, it lies in the superior
mediastinum, and is in relation on the right side with the pleura and right vagus, and near the root of the neck with the
innominate artery; on its left side are the left recurrent nerve, the aortic arch, and the left common carotid and subclavian
arteries.
The Right Bronchus (bronchus dexter), wider, shorter, and more vertical in direction than the left, is about 2.5 cm. long,
and enters the right lung nearly opposite the fifth thoracic vertebra. The azygos vein arches over it from behind; and the
right pulmonary artery lies at first below and then in front of it. About 2 cm. from its commencement it gives off a branch
to the upper lobe of the right lung. This is termed the eparterial branch of the bronchus, because it arises above the right
pulmonary artery. The bronchus now passes below the artery, and is known as the hyparterial branch; it divides into two
branches for the middle and lower lobes.
The Left Bronchus (bronchus sinister) is smaller in caliber but longer than the right, being nearly 5 cm. long. It enters the
root of the left lung opposite the sixth thoracic vertebra. It passes beneath the aortic arch, crosses in front of the esophagus,
the thoracic duct, and the descending aorta, and has the left pulmonary artery lying at first above, and then in front of it.
The left bronchus has no eparterial branch, and therefore it has been supposed by some that there is no upper lobe to the left
lung, but that the so-called upper lobe corresponds to the middle lobe of the right lung.
If a transverse section be made across the trachea a short distance above its point of bifurcation, and a bird’s-eye view
taken of its interior, the septum placed at the bottom of the trachea and separating the two bronchi will be seen to occupy
the left of the median line, and the right bronchus appears to be a more direct continuation of the trachea than the left, so
that any solid body dropping into the trachea would naturally be directed toward the right bronchus. This tendency is aided
by the larger diameter of the right tube as compared with its fellow. This fact serves to explain why a foreign body in the
trachea more frequently falls into the right bronchus
Structure - The trachea and extrapulmonary bronchi are composed of imperfect rings of hyaline cartilage, fibrous tissue,
muscular fibers, mucous membrane, and glands.
The cartilages of the trachea vary from sixteen to twenty in number: each forms an imperfect ring, which occupies the
anterior two-thirds or so of the circumference of the trachea, being deficient behind, where the tube is completed by fibrous
tissue and unstriped muscular fibers. The cartilages are placed horizontally above each other, separated by narrow intervals.
They measure about 4 mm. in depth and 1 mm. in thickness. Their outer surfaces are flattened in a vertical direction, but
the internal are convex, the cartilages being thicker in the middle than at the margins. Two or more of the cartilages often
unite, partially or completely, and they are sometimes bifurcated at their extremities. They are highly elastic, but may become calcified in advanced life. In the right bronchus the cartilages vary in number from six to eight; in the left, from nine
to twelve. They are shorter and narrower than those of the trachea, but have the same shape and arrangement. The peculiar
tracheal cartilages are the first and the last.
The first cartilage is broader than the rest, and often divided at one end; it is connected by the cricotracheal ligament with
the lower border of the cricoid cartilage, with which, or with the succeeding cartilage, it is sometimes blended.
The last cartilage is thick and broad in the middle, in consequence of its lower border being prolonged into a triangular
hook-shaped process, which curves downward and backward between the two bronchi. It ends on each side in an imperfect
ring, which encloses the commencement of the bronchus. The cartilage above the last is somewhat broader than the others
at its center.
The Fibrous Membrane. - The cartilages are enclosed in an elastic fibrous membrane, which consists of two layers; one, the
thicker, passing over the outer surface of the ring, the other over the inner surface: at the upper and lower margins of the
cartilages the two layers blend together to form a single membrane, which connects the rings one with another. They are
thus invested by the membrane. In the space behind, between the ends of the rings, the membrane forms a single layer.
The muscular tissue consists of two layers of non-striated muscle, longitudinal and transverse. The longitudinal fibers are
external, and consist of a few scattered bundles. The transverse fibers (Trachealis muscle) are internal, and form a thin layer
which extends transversely between the ends of the cartilages.
Mucous Membrane. - The mucous membrane is continuous above with that of the larynx, and below with that of the bronchi. It consists of areolar and lymphoid tissue, and presents a well-marked basement membrane, supporting a stratified epithelium, the surface layer of which is columnar and ciliated, while the deeper layers are composed of oval or rounded cells.
Beneath the basement membrane there is a distinct layer of longitudinal elastic fibers with a small amount of intervening
areolar tissue. The submucous layer is composed of a loose mesh-work of connective tissue, containing large bloodvessels,
nerves, and mucous glands; the ducts of the latter pierce the overlying layers and open on the surface
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 12. Structure and relations of lungs: lobes, segments, acinus.
The aim: to learn the anatomy of lungs, their relations; to know the topography of the lung borders and
segments.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, otorhinolaringologists, phtisyologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Lungs (Pulmones) are the essential organs of respiration; they are two in number, placed one on either side within the
thorax, and separated from each other by the heart and other contents of the mediastinum. The substance of the lung is of a
light, porous, spongy texture; it floats in water, and crepitates when handled, owing to the presence of air in the alveoli; it is
also highly elastic; hence the retracted state of these organs when they are removed from the closed cavity of the thorax.
The surface is smooth, shining, and marked out into numerous polyhedral areas, indicating the lobules of the organ: each of
these areas is crossed by numerous lighter lines.
At birth the lungs are pinkish white in color; in adult life the color is a dark slaty gray, mottled in patches; and as age advances, this mottling assumes a black color. The coloring matter consists of granules of a carbonaceous substance deposited
in the areolar tissue near the surface of the organ. It increases in quantity as age advances, and is more abundant in males
than in females. As a rule, the posterior border of the lung is darker than the anterior.
The right lung usually weighs about 625 gm., the left 567 gm., but much variation is met with according to the amount of
blood or serous fluid they may contain. The lungs are heavier in the male than in the female, their proportion to the body
being, in the former, as 1 to 37, in the latter as 1 to 43.
Each lung is conical in shape, and presents for examination an apex, a base, three borders, and two surfaces.
The apex (apex pulmonis) is rounded, and extends into the root of the neck, reaching from 2.5 to 4 cm. above the level of
the sternal end of the first rib. A sulcus produced by the subclavian artery as it curves in front of the pleura runs upward and
lateralward immediately below the apex.
The base (basis pulmonis) is broad, concave, and rests upon the convex surface of the diaphragm, which separates the
right lung from the right lobe of the liver, and the left lung from the left lobe of the liver, the stomach, and the spleen. Since
the diaphragm extends higher on the right than on the left side, the concavity on the base of the right lung is deeper than
that on the left. Laterally and behind, the base is bounded by a thin, sharp margin which projects for some distance into the
phrenicocostal sinus of the pleura, between the lower ribs and the costal attachment of the diaphragm. The base of the lung
descends during inspiration and ascends during expiration.
Surfaces. - The costal surface (facies costalis; external or thoracic surface) is smooth, convex, of considerable extent, and
corresponds to the form of the cavity of the chest, being deeper behind than in front. It is in contact with the costal pleura,
and presents, in specimens which have been hardened in situ, slight grooves corresponding with the overlying ribs.
The mediastinal surface (facies mediastinalis; inner surface) is in contact with the mediastinal pleura. It presents a deep
concavity, the cardiac impression, which accommodates the pericardium; this is larger and deeper on the left than on the
right lung, on account of the heart projecting farther to the left than to the right side of the median plane. Above and behind
this concavity is a triangular depression named the hilum, where the structures which form the root of the lung enter and
leave the viscus. These structures are invested by pleura, which, below the hilus and behind the pericardial impression,
forms the pulmonary ligament. On the right lung, immediately above the hilus, is an arched furrow which accommodates
the azygos vein; while running upward, and then arching lateralward some little distance below the apex, is a wide groove
for the superior vena cava and right innominate vein; behind this, and nearer the apex, is a furrow for the innominate artery.
Behind the hilus and the attachment of the pulmonary ligament is a vertical groove for the esophagus; this groove becomes
less distinct below, owing to the inclination of the lower part of the esophagus to the left of the middle line. In front and to
the right of the lower part of the esophageal groove is a deep concavity for the extrapericardiac portion of the thoracic part
of the inferior vena cava. On the left lung, immediately above the hilus, is a well-marked curved furrow produced by the
aortic arch, and running upward from this toward the apex is a groove accommodating the left subclavian artery; a slight
impression in front of the latter and close to the margin of the lung lodges the left innominate vein. Behind the hilus and
pulmonary ligament is a vertical furrow produced by the descending aorta, and in front of this, near the base of the lung, the
lower part of the esophagus causes a shallow impression.
Borders. - The inferior border (margo inferior) is thin and sharp where it separates the base from the costal surface and extends into the phrenicocostal sinus; medially where it divides the base from the mediastinal surface it is blunt and rounded.
The posterior border (margo posterior) is broad and rounded, and is received into the deep concavity on either side of the
vertebral column. It is much longer than the anterior border, and projects, below, into the phrenicocostal sinus.
The anterior border (margo anterior) is thin and sharp, and overlaps the front of the pericardium. The anterior border of
the right lung is almost vertical, and projects into the costomediastinal sinus; that of the left presents, below, an angular
notch, the cardiac notch, in which the pericardium is exposed. Opposite this notch the anterior margin of the left lung is
situated some little distance lateral to the line of reflection of the corresponding part of the pleura.
Fissures and Lobes of the Lungs. - The left lung is divided into two lobes, an upper and a lower, by an interlobular fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilus. As seen on the
surface, this fissure begins on the mediastinal surface of the lung at the upper and posterior part of the hilus, and runs
backward and upward to the posterior border, which it crosses at a point about 6 cm. below the apex. It then extends
downward and forward over the costal surface, and reaches the lower border a little behind its anterior extremity, and its
further course can be followed upward and backward across the mediastinal surface as far as the lower part of the hilus.
The superior lobe lies above and in front of this fissure, and includes the apex, the anterior border, and a considerable part
of the costal surface and the greater part of the mediastinal surface of the lung. The inferior lobe, the larger of the two, is
situated below and behind the fissure, and comprises almost the whole of the base, a large portion of the costal surface, and
the greater part of the posterior border.
The right lung is divided into three lobes, superior, middle, and inferior, by two interlobular fissures. One of these separates the inferior from the middle and superior lobes, and corresponds closely with the fissure in the left lung. Its direction
is, however, more vertical, and it cuts the lower border about 7.5 cm. behind its anterior extremity. The other fissure separates the superior from the middle lobe. It begins in the previous fissure near the posterior border of the lung, and, running
horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediasti-
nal surface it may be traced backward to the hilus. The middle lobe, the smallest lobe of the right lung, is wedge-shaped,
and includes the lower part of the anterior border and the anterior part of the base of the lung.
The right lung, although shorter by 2.5 cm. than the left, in consequence of the diaphragm rising higher on the right side to
accommodate the liver, is broader, owing to the inclination of the heart to the left side; its total capacity is greater and it
weighs more than the left lung.
The Root of the Lung (radix pulmonis). - A little above the middle of the mediastinal surface of each lung, and nearer its
posterior than its anterior border, is its root, by which the lung is connected to the heart and the trachea. The root is formed
by the bronchus, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, the pulmonary plexuses of
nerves, lymphatic vessels, bronchial lymph glands, and areolar tissue, all of which are enclosed by a reflection of the pleura. The root of the right lung lies behind the superior vena cava and part of the right atrium, and below the azygos vein.
That of the left lung passes beneath the aortic arch and in front of the descending aorta; the phrenic nerve, the pericardiacophrenic artery and vein, and the anterior pulmonary plexus, lie in front of each, and the vagus and posterior pulmonary
plexus behind each; below each is the pulmonary ligament.
The chief structures composing the root of each lung are arranged in a similar manner from before backward on both
sides, viz., the upper of the two pulmonary veins in front; the pulmonary artery in the middle; and the bronchus, together
with the bronchial vessels, behind. From above downward, on the two sides, their arrangement differs.
On the right side their position is - eparterial bronchus, pulmonary artery, hyparterial bronchus, pulmonary veins, but on
the left side their position is - pulmonary artery, bronchus, pulmonary veins. The lower of the two pulmonary veins, is situated below the bronchus, at the apex or lowest part of the hilus.
Divisions of the Bronchi. - Just as the lungs differ from each other in the number of their lobes, so the bronchi differ in
their mode of subdivision.
The right bronchus gives off, about 2.5 cm. from the bifurcation of the trachea, a branch for the superior lobe. This branch
arises above the level of the pulmonary artery, and is therefore named the eparterial bronchus. All the other divisions of the
main stem come off below the pulmonary artery, and consequently are termed hyparterial bronchi. The first of these is distributed to the middle lobe, and the main tube then passes downward and backward into the inferior lobe, giving off in its
course a series of large ventral and small dorsal branches. The ventral and dorsal branches arise alternately, and are usually
eight in number - four of each kind. The branch to the middle lobe is regarded as the first of the ventral series.
The left bronchus passes below the level of the pulmonary artery before it divides, and hence all its branches are hyparterial; it may therefore be looked upon as equivalent to that portion of the right bronchus which lies on the distal side of its
eparterial branch. The first branch of the left bronchus arises about 5 cm. from the bifurcation of the trachea, and is distributed to the superior lobe. The main stem then enters the inferior lobe, where it divides into ventral and dorsal branches similar to those in the right lung. The branch to the superior lobe of the left lung is regarded as the first of the ventral series.
Structure. - The lungs are composed of an external serous coat, a subserous areolar tissue and the pulmonary substance or
parenchyma.
The serous coat is the pulmonary pleura; it is thin, transparent, and invests the entire organ as far as the root.
The subserous areolar tissue contains a large proportion of elastic fibers; it invests the entire surface of the lung, and extends inward between the lobules.
The parenchyma is composed of secondary lobules which, although closely connected together by an interlobular areolar
tissue, are quite distinct from one another, and may be teased asunder without much difficulty in the fetus. The secondary
lobules vary in size; those on the surface are large, of pyramidal form, the base turned toward the surface; those in the interior smaller, and of various forms. Each secondary lobule is composed of several primary lobules, the anatomical units of
the lung. The primary lobule consists of an alveolar duct, the air spaces connected with it and their bloodvessels, lymphatics and nerves.
The intrapulmonary bronchi divide and subdivide throughout the entire organ, the smallest subdivisions constituting the
lobular bronchioles. The larger divisions consist of: (1) an outer coat of fibrous tissue in which are found at intervals irregular plates of hyaline cartilage, most developed at the points of division; (2) internal to the fibrous coat, a layer of circularly
disposed smooth muscle fibers, the bronchial muscle; and (3) most internally, the mucous membrane, lined by columnar
ciliated epithelium resting on a basement membrane. The corium of the mucous membrane contains numerous elastic fibers
running longitudinally, and a certain amount of lymphoid tissue; it also contains the ducts of mucous glands, the acini of
which lie in the fibrous coat. The lobular bronchioles differ from the larger tubes in containing no cartilage and in the fact
that the ciliated epithelial cells are cubical in shape. The lobular bronchioles are about 0.2 mm. in diameter.
Each bronchiole divides into two or more respiratory bronchioles, with scattered alveoli, and each of these again divides
into several alveolar ducts, with a greater number of alveoli connected with them. Each alveolar duct is connected with a
variable number of irregularly spherical spaces, which also possess alveoli, the atria. With each atrium a variable number
(2–5) of alveolar sacs are connected which bear on all parts of their circumference alveoli or air sacs. (Miller.)
The alveoli are lined by a delicate layer of simple squamous epithelium, the cells of which are united at their edges by
cement substance. Between the squames are here and there smaller, polygonal, nucleated cells. Outside the epithelial lining
is a little delicate connective tissue containing numerous elastic fibers and a close net-work of blood capillaries, and forming a common wall to adjacent alveoli.
The fetal lung resembles a gland in that the alveoli have a small lumen and are lined by cubical epithelium. After the first
respiration the alveoli become distended, and the epithelium takes on the characters described above.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 13. Pleura: parts, relations, sinuses. Mediastinum.
The aim: to learn the anatomy of pleura, its division on the parts, their relations, the topography of pleural
sinuses; to learn the structure, divisions and relations of mediastinum..
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, pulmonologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Pleurae
Each lung is invested by an exceedingly delicate serous membrane, the pleura, which is arranged in the form of a closed
invaginated sac. A portion of the serous membrane covers the surface of the lung and dips into the fissures between its
lobes; it is called the pulmonary pleura. The rest of the membrane lines the inner surface of the chest wall, covers the diaphragm, and is reflected over the structures occupying the middle of the thorax; this portion is termed the parietal pleura.
The two layers are continuous with one another around and below the root of the lung; in health they are in actual contact
with one another, but the potential space between them is known as the pleural cavity. When the lung collapses or when air
or fluid collects between the two layers the cavity becomes apparent. The right and left pleural sacs are entirely separate
from one another; between them are all the thoracic viscera except the lungs, and they only touch each other for a short
distance in front; opposite the second and third pieces of the sternum the interval between the two sacs is termed the mediastinum.
Different portions of the parietal pleura have received special names which indicate their position: thus, that portion which
lines the inner surfaces of the ribs and Intercostales is the costal pleura; that clothing the convex surface of the diaphragm is
the diaphragmatic pleura; that which rises into the neck, over the summit of the lung, is the cupula of the pleura (cervical
pleura); and that which is applied to the other thoracic viscera is the mediastinal pleura.
Reflections of the Pleura - Commencing at the sternum, the pleura passes lateralward, lines the inner surfaces of the costal
cartilages, ribs, and Intercostales, and at the back part of the thorax passes over the sympathetic trunk and its branches, and
is reflected upon the sides of the bodies of the vertebrae, where it is separated by a narrow interval, the posterior mediastinum, from the opposite pleura. From the vertebral column the pleura passes to the side of the pericardium, which it covers
to a slight extent; it then covers the back part of the root of the lung, from the lower border of which a triangular sheet descends vertically toward the diaphragm. This sheet is the posterior layer of a wide fold, known as the pulmonary ligament.
From the back of the lung root, the pleura may be traced over the costal surface of the lung, the apex and base, and also
over the sides of the fissures between the lobes, on to its mediastinal surface and the front part of its root. It is continued
from the lower margin of the root as the anterior layer of the pulmonary ligament, and from this it is reflected on to the pericardium (pericardial pleura), and from it to the back of the sternum. Above the level of the root of the lung, however, the
mediastinal pleura passes uninterruptedly from the vertebral column to the sternum over the structures in the superior mediastinum. Below, it covers the upper surface of the diaphragm and extends, in front, as low as the costal cartilage of the
seventh rib; at the side of the chest, to the lower border of the tenth rib on the left side and to the upper border of the same
rib on the right side; and behind, it reaches as low as the twelfth rib, and sometimes even to the transverse process of the
first lumbar vertebra. Above, its cupula projects through the superior opening of the thorax into the neck, extending from
2.5 to 5 cm. above the sternal end of the first rib; this portion of the sac is strengthened by a dome-like expansion of fascia
(Sibson’s fascia), attached in front to the inner border of the first rib, and behind to the anterior border of the transverse
process of the seventh cervical vertebra. This is covered and strengthened by a few spreading muscular fibers derived from
the Scaleni.
In the front of the chest, where the parietal pleura is reflected backward to the pericardium, the two pleural sacs are in contact for a short distance. At the upper part of the chest, behind the manubrium, they are separated by an angular interval; the
line of reflection being represented by a line drawn from the sternoclavicular articulation to the mid-point of the junction of
the manubrium with the body of the sternum. From this point the two pleurae descend in close contact to the level of the
fourth costal cartilages, and the line of reflection on the right side is continued downward in nearly a straight line to the
xiphoid process, and then turns lateralward, while on the left side the line of reflection diverges lateralward and is continued downward, close to the left border of the sternum, as far as the sixth costal cartilage. The inferior limit of the pleura is
on a considerably lower level than the corresponding limit of the lung, but does not extend to the attachment of the diaphragm, so that below the line of reflection of the pleura from the chest wall on to the diaphragm the latter is in direct contact with the rib cartilages and the Intercostales interni. Moreover, in ordinary inspiration the thin inferior margin of the
lung does not extend as low as the line of the pleural reflection, with the result that the costal and diaphragmatic pleurae are
here in contact, the intervening narrow slit being termed the phrenicocostal sinus. A similar condition exists behind the
sternum and rib cartilages, where the anterior thin margin of the lung falls short of the line of pleural reflection, and where
the slit-like cavity between the two layers of pleura forms what is called the costomediastinal sinus.
The line along which the right pleura is reflected from the chest-wall to the diaphragm starts in front, immediately below
the seventh sternocostal joint, and runs downward and backward behind the seventh costal cartilage so as to cross the tenth
rib in the mid-axillary line, from which it is prolonged to the spinous process of the twelfth thoracic vertebra. The reflection
of the left pleura follows at first the ascending part of the sixth costal cartilage, and in the rest of its course is slightly lower
than that of the right side.
The free surface of the pleura is smooth, polished, and moistened by a serous fluid; its attached surface is intimately adherent to the lung, and to the pulmonary vessels as they emerge from the pericardium; it is also adherent to the upper surface of the diaphragm: throughout the rest of its extent it is easily separable from the adjacent parts.
The right pleural sac is shorter, wider, and reaches higher in the neck than the left.
Pulmonary Ligament (ligamentum pulmonale; ligamentum latum pulmonis). - From the above description it will be seen
that the root of the lung is covered in front, above, and behind by pleura, and that at its lower border the investing layers
come into contact. Here they form a sort of mesenteric fold, the pulmonary ligament, which extends between the lower part
of the mediastinal surface of the lung and the pericardium. Just above the diaphragm the ligament ends in a free falciform
border. It serves to retain the lower part of the lung in position.
Structure of Pleura. - Like other serous membranes, the pleura is covered by a single layer of flattened, nucleated cells,
united at their edges by cement substance. These cells are modified connective-tissue corpuscles, and rest on a basement
membrane. Beneath the basement membrane there are net-works of yellow elastic and white fibers, imbedded in ground
substance which also contains connective-tissue cells. Bloodvessels, lymphatics, and nerves are distributed in the substance
of the pleura.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 4. Review of respiratory system. External nose. Nasal cavity: walls, paranasal
sinuses.
The aim: to learn the general structure and functions of respiratory system; to learn the structure of external
nose and nasal cavity, the walls of the latter, the structure, topography of paranasal sinuses, their connercion
with the nasal cavity.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, otorhinolaryngologists etc.
The External Nose (Nasus Externus; Outer Nose) is pyramidal in form, and its upper angle or root is connected directly
with the forehead; its free angle is termed the apex. Its base is perforated by two elliptical orifices, the nares, separated from
each other by an antero-posterior septum, the columna. The margins of the nares are provided with a number of stiff hairs,
or vibrissae, which arrest the passage of foreign substances carried with the current of air intended for respiration. The lateral surfaces of the nose form, by their union in the middle line, the dorsum nasi, the direction of which varies considerably
in different individuals; the upper part of the dorsum is supported by the nasal bones, and is named the bridge. The lateral
surface ends below in a rounded eminence, the ala nasi.
Structure. - The frame-work of the external nose is composed of bones and cartilages; it is covered by the integument, and
lined by mucous membrane.
The bony frame-work occupies the upper part of the organ; it consists of the nasal bones, and the frontal processes of the
maxillae.
The cartilaginous frame-work (cartilagines nasi) consists of five large pieces, viz., the cartilage of the septum, the two
lateral and the two greater alar cartilages, and several smaller pieces, the lesser alar cartilages. The various cartilages are
connected to each other and to the bones by a tough fibrous membrane.
The cartilage of the septum (cartilago septi nasi) is somewhat quadrilateral in form, thicker at its margins than at its center,
and completes the separation between the nasal cavities in front. Its anterior margin, thickest above, is connected with the
nasal bones, and is continuous with the anterior margins of the lateral cartilages; below, it is connected to the medial crura
of the greater alar cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular plate of the ethmoid;
its inferior margin with the vomer and the palatine processes of the maxillae.
It may be prolonged backward (especially in children) as a narrow process, the sphenoidal process, for some distance between the vomer and perpendicular plate of the ethmoid. The septal cartilage does not reach as far as the lowest part of the
nasal septum. This is formed by the medial crura of the greater alar cartilages and by the skin; it is freely movable, and
hence is termed the septum mobile nasi.
The lateral cartilage (cartilago nasi lateralis; upper lateral cartilage) is situated below the inferior margin of the nasal
bone, and is flattened, and triangular in shape. Its anterior margin is thicker than the posterior, and is continuous above with
the cartilage of the septum, but separated from it below by a narrow fissure; its superior margin is attached to the nasal
bone and the frontal process of the maxilla; its inferior margin is connected by fibrous tissue with the greater alar cartilage.
The greater alar cartilage (cartilago alaris major; lower lateral cartilage) is a thin, flexible plate, situated immediately
below the preceding, and bent upon itself in such a manner as to form the medial and lateral walls of the naris of its own
side. The portion which forms the medial wall (crus mediale) is loosely connected with the corresponding portion of the
opposite cartilage, the two forming, together with the thickened integument and subjacent tissue, the septum mobile nasi.
The part which forms the lateral wall (crus laterale) is curved to correspond with the ala of the nose; it is oval and flattened,
narrow behind, where it is connected with the frontal process of the maxilla by a tough fibrous membrane, in which are
found three or four small cartilaginous plates, the lesser alar cartilages (cartilagines alares minores; sesamoid cartilages).
Above, it is connected by fibrous tissue to the lateral cartilage and front part of the cartilage of the septum; below, it falls
short of the margin of the naris, the ala being completed by fatty and fibrous tissue covered by skin. In front, the greater
alar cartilages are separated by a notch which corresponds with the apex of the nose.
The integument of the dorsum and sides of the nose is thin, and loosely connected with the subjacent parts; but over the
tip and alae it is thicker and more firmly adherent, and is furnished with a large number of sebaceous follicles, the orifices
of which are usually very distinct.
The arteries of the external nose are the alar and septal branches of the external maxillary, which supply the alae and septum; the dorsum and sides being supplied from the dorsal nasal branch of the ophthalmic and the infraorbital branch of the
internal maxillary. The veins end in the anterior facial and ophthalmic veins.
The nerves for the muscles of the nose are derived from the facial, while the skin receives branches from the infratrochlear
and nasociliary branches of the ophthalmic, and from the infraorbital of the maxillary.
The Nasal Cavity (Cavum Nasi; Nasal Fossa) - The nasal chambers are situated one on either side of the median plane.
They open in front through the nares, and communicate behind through the choanae with the nasal part of the pharynx. The
nares are somewhat pear-shaped apertures, each measuring about 2.5 cm. antero-posteriorly and 1.25 cm. transversely at its
widest part. The choanae are two oval openings each measuring 2.5 cm. in the vertical, and 1.25 cm. in the transverse direction in a well-developed adult skull.
Inside the aperture of the nostril is a slight dilatation, the vestibule, bounded laterally by the ala and lateral crus of the
greater alar cartilage, and medially by the medial crus of the same cartilage. It is lined by skin containing hairs and sebaceous glands, and extends as a small recess toward the apex of the nose. Each nasal cavity, above and behind the vestibule,
is divided into two parts: an olfactory region, consisting of the superior nasal concha and the opposed part of the septum,
and a respiratory region, which comprises the rest of the cavity.
Lateral Wall - On the lateral wall are the superior, middle, and inferior nasal conchae, and below and lateral to each concha is the corresponding nasal passage or meatus. Above the superior concha is a narrow recess, the sphenoethmoidal recess, into which the sphenoidal sinus opens. The superior meatus is a short oblique passage extending about half-way along
the upper border of the middle concha; the posterior ethmoidal cells open into the front part of this meatus. The middle meatus is below and lateral to the middle concha, and is continued anteriorly into a shallow depression, situated above the
vestibule and named the atrium of the middle meatus. On raising or removing the middle concha the lateral wall of this
meatus is fully displayed. On it is a rounded elevation, the bulla ethmoidalis, and below and in front of this is a curved
cleft, the hiatus semilunaris.
The bulla ethmoidalis is caused by the bulging of the middle ethmoidal cells which open on or immediately above it, and
the size of the bulla varies with that of its contained cells.
The hiatus semilunaris is bounded inferiorly by the sharp concave margin of the uncinate process of the ethmoid bone, and
leads into a curved channel, the infundibulum, bounded above by the bulla ethmoidalis and below by the lateral surface of
the uncinate process of the ethmoid. The anterior ethmoidal cells open into the front part of the infundibulum, and this in
slightly over 50 per cent. of subjects is directly continuous with the frontonasal duct or passage leading from the frontal air
sinus; but when the anterior end of the uncinate process fuses with the front part of the bulla, this continuity is interrupted
and the frontonasal duct then opens directly into the anterior end of the middle meatus.
Below the bulla ethmoidalis, and partly hidden by the inferior end of the uncinate process, is the ostium maxillare, or
opening from the maxillary sinus; in a frontal section this opening is seen to be placed near the roof of the sinus. An accessory opening from the sinus is frequently present below the posterior end of the middle nasal concha. The inferior meatus is
below and lateral to the inferior nasal concha; the nasolacrimal duct opens into this meatus under cover of the anterior part
of the inferior concha.
Medial Wall. - The medial wall or septum is frequently more or less deflected from the median plane, thus lessening the
size of one nasal cavity and increasing that of the other; ridges or spurs of bone growing into one or other cavity from the
septum are also sometimes present. Immediately over the incisive canal at the lower edge of the cartilage of the septum a
depression, the nasopalatine recess, is seen. In the septum close to this recess a minute orifice may be discerned; it leads
backward into a blind pouch, the rudimentary vomeronasal organ of Jacobson, which is supported by a strip of cartilage,
the vomeronasal cartilage. This organ is well-developed in many of the lower animals, where it apparently plays a part in
the sense of smell, since it is supplied by twigs of the olfactory nerve and lined by epithelium similar to that in the olfactory
region of the nose.
The roof of the nasal cavity is narrow from side to side, except at its posterior part, and may be divided, from behind forward, into sphenoidal, ethmoidal, and frontonasal parts, after the bones which form it.
The floor is concave from side to side and almost horizontal antero-posteriorly; its anterior three-fourths are formed by
the palatine process of the maxilla, its posterior fourth by the horizontal process of the palatine bone. In its anteromedial
part, directly over the incisive foramen, a small depression, the nasopalatine recess, is sometimes seen; it points downward
and forward and occupies the position of a canal which connected the nasal with the buccal cavity in early fetal life.
The Accessory Sinuses of the Nose (Sinus Paranasales) or air cells of the nose are the frontal, ethmoidal, sphenoidal, and
maxillary; they vary in size and form in different individuals, and are lined by ciliated mucous membrane directly continuous with that of the nasal cavities.
The Frontal Sinuses (sinus frontales), situated behind the superciliary arches, are rarely symmetrical, and the septum
between them frequently deviates to one or other side of the middle line. Their average measurements are as follows:
height, 3 cm.; breadth, 2.5 cm.; depth from before backward, 2.5 cm. Each opens into the anterior part of the corresponding
middle meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid.
Absent at birth, they are generally fairly well developed between the seventh and eighth years, but only reach their full size
after puberty.
The Ethmoidal Air Cells (cellulae ethmoidales) consist of numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine. They lie between the upper parts of the nasal
cavities and the orbits, and are separated from these cavities by thin bony laminae. On either side they are arranged in three
groups, anterior, middle, and posterior. The anterior and middle groups open into the middle meatus of the nose, the former
by way of the infundibulum, the latter on or above the bulla ethmoidalis. The posterior cells open into the superior meatus
under cover of the superior nasal concha; sometimes one or more opens into the sphenoidal sinus. The ethmoidal cells
begin to develop during fetal life.
The Sphenoidal Sinuses (sinus sphenoidales) contained within the body of the sphenoid vary in size and shape; owing to
the lateral displacement of the intervening septum they are rarely symmetrical. The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm. When exceptionally large they
may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone.
Each sinus communicates with the sphenoethmoidal recess by means of an aperture in the upper part of its anterior wall.
They are present as minute cavities at birth, but their main development takes place after puberty.
The Maxillary Sinus (sinus maxillaris; antrum of Highmore), the largest of the accessory sinuses of the nose, is a pyramidal cavity in the body of the maxilla. Its base is formed by the lateral wall of the nasal cavity, and its apex extends into the
zygomatic process. Its roof or orbital wall is frequently ridged by the infra-orbital canal, while its floor is formed by the
alveolar process and is usually 1/2 to 10 mm. below the level of the floor of the nose; projecting into the floor are several
conical elevations corresponding with the roots of the first and second molar teeth, and in some cases the floor is perforated
by one or more of these roots. The size of the sinus varies in different skulls, and even on the two sides of the same skull.
The adult capacity varies from 9.5 c.c. to 20 c.c., average about 14.75 c.c. The following measurements are those of an average-sized sinus: vertical height opposite the first molar tooth, 3.75 cm.; transverse breadth, 2.5 cm.; antero-posterior
depth, 3 cm. In the antero-superior part of its base is an opening through which it communicates with the lower part of the
hiatus semilunaris; a second orifice is frequently seen in, or immediately behind, the hiatus. The maxillary sinus appears as
a shallow groove on the medial surface of the bone about the fourth month of fetal life, but does not reach its full size until
after the second dentition. 142 At birth it measures about 7 mm. in the dorso-ventral direction and at twenty months about
20 mm.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 5. Development, anatomy and relations of respiratory system.
The aim: to learn the development of the respiratory apparatus, estimation of its topography and relations.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, thoracal surgeons etc.
Development. - The rudiment of the respiratory organs appears as a median longitudinal groove in the ventral wall of the
pharynx. The groove deepens and its lips fuse to form a septum which grows from below upward and converts the groove
into a tube, the laryngo-tracheal tube, the cephalic end of which opens into the pharynx by a slit-like aperture formed by the
persistent anterior part of the groove. The tube is lined by entoderm from which the epithelial lining of the respiratory tract
is developed. The cephalic part of the tube becomes the larynx, and its next succeeding part the trachea, while from its caudal end two lateral outgrowths, the right and left lung buds, arise, and from them the bronchi and lungs are developed. The
first rudiment of the larynx consists of two arytenoid swellings, which appear, one on either side of the cephalic end of the
laryngo-tracheal groove, and are continuous in front of the groove with a transverse ridge (furcula of His) which lies between the ventral ends of the third branchial arches and from which the epiglottis is subsequently. After the separation of
the trachea from the esophagus the arytenoid swellings come into contact with one another and with the back of the epiglottis, and the entrance to the larynx assumes the form of a T-shaped cleft, the margins of the cleft adhere to one another and
the laryngeal entrance is for a time occluded. The mesodermal wall of the tube becomes condensed to form the cartilages of
the larynx and trachea. The arytenoid swellings are differentiated into the arytenoid and corniculate cartilages, and the folds
joining them to the epiglottis form the aryepiglottic folds in which the cuneiform cartilages are developed as derivatives of
the epiglottis. The thyroid cartilage appears as two lateral plates, each chondrified from two centers and united in the midventral line by membrane in which an additional center of chondrification develops. The cricoid cartilage arises from two
cartilaginous centers, which soon unite ventrally and gradually extend and ultimately fuse on the dorsal aspect of the tube.
The opening of the pulmonary diverticulum lies between the two fifth arch masses and behind a “central mass” in the
middle line - the proximal end of the diverticulum is compressed between the fifth arch masses. The fifth arch is joined by
the fourth to form a “lateral mass” on each side of the opening, and these “lateral masses” grow forward and overlap the
central mass and so form a secondary transverse cavity, which is really a part of the cavity of the pharynx. The two parts of
the cavity of the larynx are separated in the adult by a line drawn back along the vocal fold and then upward along the border of the arytenoid eminence to the interarytenoid notch. The arytenoid and cricoid are developed in the fifth arch mass.
The thyroid is primarily a fourth arch derivative, and if it has a fifth arch element this is a later addition. The epiglottis is
derived from the “central mass,” and has a third arch element in its oral and upper aspect; the arch value of the “central
mass” is doubtful.
The right and left lung buds grow out behind the ducts of Cuvier, and are at first symmetrical, but their ends soon become
lobulated, three lobules appearing on the right, and two on the left; these subdivisions are the early indications of the corresponding lobes of the lungs. The buds undergo further subdivision and ramification, and ultimately end in minute expanded
extremities - the infundibula of the lung. After the sixth month the air-sacs begin to make their appearance on the infundibula in the form of minute pouches. The pulmonary arteries are derived from the sixth aortic arches. During the course of
their development the lungs migrate in a caudal direction, so that by the time of birth the bifurcation of the trachea is opposite the fourth thoracic vertebra. As the lungs grow they project into that part of the celom which will ultimately form the
pleural cavities, and the superficial layer of the mesoderm enveloping the lung rudiment expands on the growing lung and
is converted into the pulmonary pleura.
In stage 10 (28 days) 10 the cranial,section of the intraembryonic coelom consists of a middle part, the pericardial cavity,
and two thin canals laterally, the pericardioperitoneal canals.
They connect the pericardial cavity with the part of the intraembryonic coelom that is open towards the outside, the future
peritoneal cavity. At this point no pleural cavity yet exists because the lungs have not yet begun to develop.
In stage 12 the peritoneal cavity is connected with the pericardial cavity via the pericardio-peritoneal canals. From the
foregut in the middle, the lung buds will soon sprout on both sides into the pericardio- peritoneal canals. Observe the proximity of the heart and liver anlagen.
In stage 13 (32 days) the lung buds grow into the pericardioperitoneal canals and dent them. Thereby the pericardioperitoneal canals are subdivided on both sides by these lung buds that are sprouting in from the medial direction.
With the increase in size of the lung anlage the pericardioperitoneal canal widens to become the pleural cavity that is separated from the pericardial cavity by the pleuropericardial membrane and from the peritoneal cavity by the pleuroperitoneal
membrane.
In the region of the peritoneal cavity and the umbilical coelom, the left and right peritoneal tubes join ventrally to form a
common cavity, the peritoneal cavity, that goes over into the umbilical coelom. In the dorsal region they form the meso of
the guts.
In the cut-open coelom cavity one sees the intraperitoneal organs that are coated with mesothelium: the stomach and liver,
as well as the urogenital ridge.
The lungs become covered by the visceral layer of the pleural cavity, the pleura visceralis. Towards the outside, the pleural
cavity is bounded by the parietal layer, the pleura parietalis. Through their rapid increase in size the two lungs, left and
right, enclose the heart that is in their middle.
Visceral Structures of the Thorax - Arranged Alphabetically
Organ/Part of Organ
Location/Description
apex
tip of the left ventricle of the heart
atrioventricular bundle
part of the conduction system of the heart
atrioventricular node
part of the conduction system of the heart
atrioventricular valve, left
heart valve located between the left atrium
and the left ventricle
atrioventricular valve, right
atrioventricular node between the right atrium and the right ventricle
chamber of the heart that receives deoxygenated blood from the systemic circulation
(body)
atrium, right
Notes
apex of the heart is located 3" to the left of
the midline at the level of the 5th intercostal
space
atrioventricular bundle is a strand of specialized myocardium that passes through
the right fibrous trigone into the muscular
part of the interventricular septum; it divides into right and left branches to supply
the ventricles; also known as: bundle of His
atrioventricular node is located in the wall
of the right atrium above the opening of the
coronary sinus and the septal cusp of the
tricuspid valve
left atrioventricular valve has two valve
cusps; also known as: mitral or bicuspid
valve
right atrioventricular valve has three valve
cusps; also known as: tricuspid valve
right atrium forms the right margin of the
heart; it receives blood from the superior
vena cava, inferior vena cava and coronary
atrium, left
auricle
chamber of the heart that receives oxygenated blood from the pulmonic circulation
(lungs)
small appendage that projects anteriorly
from the atrium
base
the superior aspect of heart
bronchi
the air conducting passages of the lungs
bronchus, primary
first branch of the air conducting system
arising from the bifurcation of the trachea at
T4/T5 intervertebral disc
bronchus, secondary
a branch of the air conducting system arising from the primary bronchus
bronchus, tertiary
a branch of the air conducting system arising from the secondary (lobar) bronchus
bronchus, segmental
a branch of the air conducting system arising from the secondary (lobar) bronchus
carina
keel-shaped cartilage lying within the tracheal bifurcation
thin connective tissue cords that attach the
atrioventricular valve cusps to the papillary
mm.
groove on the surface of the heart that separates the atria from the ventricles
chordae tendineae
coronary sulcus
sinus
left atrium is located on the posterior aspect
of the heart; it receives blood from the pulmonary vv.
paired, one on each atrium; right auricle lies
beside the aorta and covers the right coronary artery; left auricle lies beside the pulmonary trunk
base of the heart is where the aorta, pulmonary trunk and superior vena cava exit/enter
the heart
bronchi may be classified as primary, secondary (lobar), and tertiary (segmental)
paired, right and left; one primary bronchus
enters the hilus of each lung; the right primary bronchus is shorter, larger in diameter
and more vertically oriented than the left so
that aspirated foreign bodies tend to lodge
in the right primary bronchus
there are 3 secondary bronchi in the right
lung: upper, middle, lower; there are 2 secondary bronchi in the left lung: upper, lower; also known as: lobar bronchi
there are 10 tertiary bronchi in the right
lung: branching from the right superior lobar bronchus - apical, anterior, posterior;
branching from the right middle lobar bronchus - medial, lateral; branching from the
right inferior lobar bronchus - superior, anterior basal, posterior basal, medial basal,
lateral basal; there are 8 tertiary bronchi in
the left lung: branching from the left superior lobar bronchus - apicoposterior, anterior; branching from the lingular bronchus
(off of the superior lobar bronchus) - superior lingular, inferior lingular; branching
from the inferior lobar bronchus - superior,
anteromedial basal, posterior basal, lateral
basal; also known as: segmental bronchi
there are 10 tertiary bronchi in the right
lung: branching from the right superior lobar bronchus - apical, anterior, posterior;
branching from the right middle lobar bronchus - medial, lateral; branching from the
right inferior lobar bronchus - superior, anterior basal, posterior basal, medial basal,
lateral basal; there are 8 tertiary bronchi in
the left lung: branching from the left superior lobar bronchus - apicoposterior, anterior; branching from the lingular bronchus
(off of the superior lobar bronchus) - superior lingular, inferior lingular; branching
from the inferior lobar bronchus - superior,
anteromedial basal, posterior basal, lateral
basal; also known as: segmental bronchi
carina trachealis is an important landmark
during endoscopy of the bronchial tree
chordae tendineae are found only in the
ventricles, not in the atria
coronary sulcus contains the coronary sinus,
circumflex a., and right coronary a.
crista terminalis
ridge of cardiac muscle separating the
smooth sinus venarum posteriorly from the
roughened wall of the primitive atrium anteriorly
serous membrane lining the pleural cavity
which extends above the level of the 1st rib
into the root of the neck
cupula
esophagus
the portion of the gastrointestinal tract between the pharynx and the stomach
fissure, oblique
deep groove in the surface of the lung that
separates the upper lobe from the lower
lobe (both lungs), and the middle lobe from
the lower lobe (right lung)
deep groove in the surface of the lung that
separates the middle lobe from the upper
lobe (right lung only)
shallow depression in the left wall of the
right atrium
fissure, horizontal
fossa ovalis
heart
interventricular
anterior
sulcus,
interventricular
posterior
sulcus,
ligamentum arteriosum
limbus fossa ovalis
lobe, inferior
muscular pump for blood located within
middle mediastinum of the thorax
groove between the ventricles on the anterior surface of the heart
groove between the ventricles on the diaphragmatic surface of the heart
fibrous cord of connective tissue that connects the left pulmonary a. near its origin
with the undersurface of the aortic arch
the ridge around the fossa ovalis in the left
wall of the right atrium
the portion of the lung supplied by the inferior lobar bronchus
lobe, middle
the portion of the right lung supplied by the
middle lobar bronchus
lobe, superior
the portion of the lung supplied by the superior lobar bronchus
the sinuatrial node lies within the superior
end of the crista terminalis
cupular pleura is continuous inferiorly with
the costal and mediastinal parietal pleurae;
it is reinforced by a specialization of scalene fascia (called Sibson's fascia or suprapleural membrane); also known as: cervical parietal pleura or cervical dome of
pleura
connects: superiorly with laryngopharynx at
lower border of cricoid cartilage; inferiorly
it passes through diaphragm at the T10 vertebral level to reach the stomach; the upper
1/3 is skeletal muscle innervated by the
recurrent laryngeal, the lower 2/3rds is
smooth muscle innervated by the vagus nn.
via the esophageal plexus
oblique fissure extends from the level of the
T3 vertebra posteriorly to the 6th costochondral junction anteriorly
horizontal fissure extends from the 5th rib
at the mid-axillary line along the 4th rib to
the sternum anteriorly
fossa ovalis is the remnant of the foramen
ovale which provided an open communication between the right atrium and left atrium
in the fetus
heart is nearly surrounded by the pericardial
sac and pericardial cavity
anterior interventricular sulcus contains the
anterior interventricular a. and the great
cardiac v.; it marks the location of the interventricular septum
posterior interventricular sulcus contains the
posterior interventricular a. and the middle
cardiac v.; it marks the location of the interventricular septum
ligamentum arteriosum is a remnant of the
ductus arteriosus; the left recurrent laryngeal n. passes beneath it
limbus fossa ovalis is the margin of the septum secundum
inferior lobe of the right lung: possesses 5
bronchopulmonary segments - superior,
anterior basal, posterior basal, medial basal,
lateral basal; inferior lobe of the left lung:
possesses 4 bronchopulmonary segments superior, anteromedial basal, posterior basal, lateral basal
middle lobe is found in the right lung only;
it possesses 2 bronchopulmonary segments:
medial and lateral; lingula of the inferior
lobe of the left lung is equivalent to the
middle lobe of the right lung
superior lobe of the right lung: possesses
three bronchopulmonary segments - apical,
anterior and posterior; superior lobe of the
left lung: possesses four bronchopulmonary
segments - apicoposterior, anterior, superior
lung
mitral valve
moderator band
papillary muscle
pectinate muscles
pericardial sinus, oblique
the portion of the respiratory system where
exchange of gasses occurs between the air
and the blood; located in the thoracic cavity
heart valve located between the left atrium
and the left ventricle
ridge of cardiac muscle spanning from the
interventricular septum to the anterior papillary m. in the right ventricle
a small, nipple-like projection of cardiac
muscle located within the ventricles
prominent ridges of myocardium located on
the inner surface of the right atrium
an area of the pericardial cavity located
behind the left atrium of heart
pericardial sinus, transverse
an area of the pericardial cavity located
behind the aorta and pulmonary trunk and
anterior to the superior vena cava
pericardium, fibrous
a fibrous sac that attaches to the central tendon of the diaphragm and fuses with the
adventitia of the great vessels superiorly
pericardium, parietal serous
serous membrane lining the pericardial cavity; it is located on the inner surface of the
fibrous pericardium
pericardium, visceral serous
serous membrane covering the surface of
the heart
pleura
serous membrane lining the pleural cavity
pleura, cervical parietal
serous membrane lining the pleural cavity
which extends above the level of the 1st rib
into the root of the neck
pleura, costal parietal
serous membrane lining the pleural cavity
on the inner surfaces of the ribs, costal cartilages, and intercostal mm.
lingular, inferior lingular
paired; right lung is divided into three
lobes: superior, middle and inferior; left
lung has two lobes: superior and inferior
mitral valve has two valve cusps; it is
named for the similarity of its shape to that
of a bishop's miter; also known as: left atrioventricular valve or bicuspid valve
septomarginal trabecula contains part of the
right branch of the atrioventricular bundle;
also known as: septomarginal trabecula
papillary muscles attach to the cusps of the
atrioventricular valves via chordae tendineae and act to keep the valve cusps from prolapsing under systolic blood pressure; there
are three in the right atrium: anterior, posterior, septal; there are two in the left atrium:
anterior, posterior
pectinate muscles are very pronounced in
the right atrium and in both auricles
serous pericardium reflects onto the inferior
vena cava and pulmonary vv. to define this
space
transverse pericardial sinus was a simple
structure when the heart tube began to form
during development; it separates the outflow vessels from the inflow vessels of the
heart
fibrous pericardium contains the pericardial
cavity and heart; it is lined on its inner surface by the parietal layer of serous pericardium; it defines the outermost boundary of
the middle mediastinum
parietal serous pericardium reflects onto the
heart at the origins of the great vessels to
become continuous with the visceral serous
pericardium
visceral serous pericardium reflects onto the
inner surface of the fibrous pericardium at
the origins of the great vessels to become
continuous with the parietal serous pericardium; also known as: epicardium
there are two types of pleura: visceral pleura covers the lungs, parietal pleura lines the
inner surfaces of the walls of pleural cavity;
parietal pleura is sensitive to pain but visceral pleura is not sensitive to pain
cervical parietal pleura is continuous inferiorly with the costal and mediastinal parietal
pleurae; it is reinforced by a specialization
of scalene fascia (called Sibson's fascia or
suprapleural membrane); also known as:
cupula or cervical dome of pleura
costal parietal pleura is continuous anteriorly with the mediastinal parietal pleura at the
costomediastinal reflection; it is continuous
posteriorly with the mediastinal parietal
pleural at the vertebral bodies; it is continuous inferiorly with the diaphragmatic parietal pleura at the costodiaphragmatic reflection; it is continuous superiorly with the
cervical parietal pleura at the level of the 1st
pleura,
parietal
diaphragmatic
serous membrane lining the pleural cavity
on the superior surface of the diaphragm
pleura, mediastinal parietal
serous membrane lining the pleural cavity
on the lateral surface of the mediastinum
pleura, visceral
serous membrane lining the surfaces of the
lungs
pulmonary conus
smooth area of the right ventricle below the
opening into the pulmonary trunk
pulmonary ligament
fold of pleura located below the root of the
lung
semilunar valves
valve with three pocket-shaped cusps located in the base of the pulmonary trunk and
ascending aorta
septomarginal trabecula
ridge of cardiac muscle spanning from the
interventricular septum to the anterior papillary m. in the right ventricle
part of the conduction system of the heart
sinuatrial node
sulcus terminalis
trabeculae carnae
trachea
tricuspid valve
ventricle, right
ventricle, left
groove on the external surface of the right
atrium marking the location of the crista
terminalis
ridges of cardiac muscle located on the inner wall of both ventricles
main airway that lies anterior to the esophagus
a three cusped valve located at the ostium
between the right atrium and the right ventricle
heart chamber that pumps blood to the pulmonary circulation
heart chamber that pumps blood to the systemic circulation
rib
diaphragmatic parietal pleura is continuous
superiorly with the costal parietal pleura at
the costodiaphragmatic reflection; it is continuous superiorly with the mediastinal
pleura at the inferomedial borders of the
pleural cavities
mediastinal parietal pleura is continuous
anteriorly with the costal parietal pleura at
the costomediastinal reflection; it is continuous inferiorly with the diaphragmatic pleura at the inferomedial borders of the pleural
cavities; it is continuous posteriorly with the
costal parietal pleura lateral to the vertebral
bodies; it is continuous superiorly with the
cervical pleura at the level of the 1st rib
visceral pleura extends into the oblique and
horizontal fissures of the lungs; it does not
have pain fibers
pulmonary conus is the pulmonary part of
the conus cordis which divides during development to form the outflow portions of
the right and left ventricles
pulmonary ligament is where the visceral
pleura and the mediastinal parietal pleura
are continuous with each other
semilunar valve has a thin endothelial free
margin on each cusp called a lunula; a
dense nodule is located at the midpoint of
the free margin of each valve cusp; the
pulmonary semilunar valve has anterior, left
and right cusps; the aortic semilunar valve
has right, left and posterior cusps
septomarginal trabecula contains part of the
right branch of the atrioventricular bundle;
also known as: moderator band
sinuatrial node is located within the crista
terminalis near the superior vena cava; it is
the "pacemaker" of the heart
the sinuatrial node is located at the superior
end of the crista terminalis
the word trabecula is derived from the Latin
word trabs, which means a beam
trachea extends from vertebral level C6 to
the level of the T4/5 intervertebral disc;
superiorly it is connected to the cricoid cartilage via the cricotracheal ligament; it bifurcates into two primary bronchi
tricuspid valve possesses anterior, posterior
and septal cusps; also known as: right atrioventricular valve
right ventricle has a septomarginal trabecula
and 3 papillary mm.; it pumps blood into
the pulmonary trunk
left ventricle has 2 papillary mm.; it pumps
blood into the ascending aorta
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
UNIT 9. UROGENITAL AND ENDOCRINE SYSTEM
Practice class 14. Written tests and examination of practice skills on respiratory system. Examination of self-taught tasks. Review of urinary system.
Practice class 15. Structure, function and relations of kidneys.
The aim: to learn the external and internal structure of kidneys, their relations and ligaments; to understand
peculiarities of kidney fixation apparatus.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, nephrologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Kidneys (Renes) are situated in the posterior part of the abdomen, one on either side of the vertebral column, behind
the peritoneum, and surrounded by a mass of fat and loose areolar tissue. Their upper extremities are on a level with the
upper border of the twelfth thoracic vertebra, their lower extremities on a level with the third lumbar. The right kidney is
usually slightly lower than the left, probably on account of the vicinity of the liver. The long axis of each kidney is directed
downward and lateralward; the transverse axis backward and lateralward.
Each kidney is about 11.25 cm. in length, 5 to 7.5 cm. in breadth, and rather more than 2.5 cm. in thickness. The left is
somewhat longer, and narrower, than the right. The weight of the kidney in the adult male varies from 125 to 170 gm., in
the adult female from 115 to 155 gm. The combined weight of the two kidneys in proportion to that of the body is about 1
to 240.
The kidney has a characteristic form, and presents for examination two surfaces, two borders, and an upper and lower extremity.
Relations. - The anterior surface (facies anterior) of each kidney is convex, and looks forward and lateralward. Its relations
to adjacent viscera differ so completely on the two sides that separate descriptions are necessary.
Anterior Surface of Right Kidney. - A narrow portion at the upper extremity is in relation with the right suprarenal gland. A
large area just below this and involving about three-fourths of the surface, lies in the renal impression on the inferior surface of the liver, and a narrow but somewhat variable area near the medial border is in contact with the descending part of
the duodenum. The lower part of the anterior surface is in contact laterally with the right colic flexure, and medially, as a
rule, with the small intestine. The areas in relation with the liver and small intestine are covered by peritoneum; the suprarenal, duodenal, and colic areas are devoid of peritoneum.
Anterior Surface of Left Kidney. - A small area along the upper part of the medial border is in relation with the left suprarenal gland, and close to the lateral border is a long strip in contact with the renal impression on the spleen. A somewhat
quadrilateral field, about the middle of the anterior surface, marks the site of contact with the body of the pancreas, on the
deep surface of which are the lienal vessels. Above this is a small triangular portion, between the suprarenal and splenic
areas, in contact with the postero-inferior surface of the stomach. Below the pancreatic area the lateral part is in relation
with the left colic flexure, the medial with the small intestine. The areas in contact with the stomach and spleen are covered
by the peritoneum of the omental bursa, while that in relation to the small intestine is covered by the peritoneum of the
general cavity; behind the latter are some branches of the left colic vessels. The suprarenal, pancreatic, and colic areas are
devoid of peritoneum.
The Posterior Surface (facies posterior) of each kidney is directed backward and medialward. It is imbedded in areolar
and fatty tissue and entirely devoid of peritoneal covering. It lies upon the diaphragm, the medial and lateral lumbocostal
arches, the Psoas major, the Quadratus lumborum, and the tendon of the Transversus abdominis, the subcostal, and one or
two of the upper lumbar arteries, and the last thoracic, iliohypogastric, and ilioinguinal nerves. The right kidney rests upon
the twelfth rib, the left usually on the eleventh and twelfth. The diaphragm separates the kidney from the pleura, which dips
down to form the phrenicocostal sinus, but frequently the muscular fibers of the diaphragm are defective or absent over a
triangular area immediately above the lateral lumbocostal arch, and when this is the case the perinephric areolar tissue is in
contact with the diaphragmatic pleura.
Borders. - The lateral border (margo lateralis; external border) is convex, and is directed toward the postero-lateral wall of
the abdomen. On the left side it is in contact at its upper part, with the spleen.
The medial border (margo medialis; internal border) is concave in the center and convex toward either extremity; it is
directed forward and a little downward. Its central part presents a deep longitudinal fissure, bounded by prominent overhanging anterior and posterior lips. This fissure is named the hilum, and transmits the vessels, nerves, and ureter. Above the
hilum the medial border is in relation with the suprarenal gland; below the hilum, with the ureter.
Extremities. - The superior extremity (extremitas superior) is thick and rounded, and is nearer the median line than the
lower; it is surmounted by the suprarenal gland, which covers also a small portion of the anterior surface.
The inferior extremity (extremitas inferior) is smaller and thinner than the superior and farther from the median line. It
extends to within 5 cm. of the iliac crest.
The relative position of the main structures in the hilum is as follows: the vein is in front, the artery in the middle, and the
ureter behind and directed downward. Frequently, however, branches of both artery and vein are placed behind the ureter.
Fixation of the Kidney - The kidney and its vessels are imbedded in a mass of fatty tissue, termed the adipose capsule,
which is thickest at the margins of the kidney and is prolonged through the hilum into the renal sinus. The kidney and the
adipose capsule are enclosed in a sheath of fibrous tissue continuous with the subperitoneal fascia, and named the renal
fascia. At the lateral border of the kidney the renal fascia splits into an anterior and a posterior layer. The anterior layer is
carried medialward in front of the kidney and its vessels, and is continuous over the aorta with the corresponding layer of
the opposite side. The posterior layer extends medialward behind the kidney and blends with the fascia on the Quadratus
lumborum and Psoas major, and through this fascia is attached to the vertebral column. Above the suprarenal gland the two
layers of the renal fascia fuse, and unite with the fascia of the diaphragm; below they remain separate, and are gradually
lost in the subperitoneal fascia of the iliac fossa. The renal fascia is connected to the fibrous tunic of the kidney by numerous trabeculae, which traverse the adipose capsule, and are strongest near the lower end of the organ. Behind the fascia
renalis is a considerable quantity of fat, which constitutes the paranephric body. The kidney is held in position partly
through the attachment of the renal fascia and partly by the apposition of the neighboring viscera.
General Structure of the Kidney. - The kidney is invested by a fibrous tunic, which forms a firm, smooth covering to the
organ. The tunic can be easily stripped off, but in doing so numerous fine processes of connective tissue and small
bloodvessels are torn through. Beneath this coat a thin, wide-meshed net-work of unstriped muscular fiber forms an incomplete covering to the organ. When the capsule is stripped off, the surface of the kidney is found to be smooth and even and
of a deep red color. In infants fissures extending for some depth may be seen on the surface of the organ, a remnant of the
lobular construction of the gland. The kidney is dense in texture, but is easily lacerable by mechanical force. If a vertical
section of the kidney be made from its convex to its concave border, it will be seen that the hilum expands into a central
cavity, the renal sinus, this contains the upper part of the renal pelvis and the calyces, surrounded by some fat in which are
imbedded the branches of the renal vessels and nerves. The renal sinus is lined by a prolongation of the fibrous tunic, which
is continued around the lips of the hilum. The renal calyces, from seven to thirteen in number, are cup-shaped tubes, each
of which embraces one or more of the renal papillae; they unite to form two or three short tubes, and these in turn join to
form a funnel-shaped sac, the renal pelvis. The renal pelvis, wide above and narrow below where it joins the ureter, is partly outside the renal sinus. The renal calyces and pelvis form the upper expanded end of the excretory duct of the kidney.
The kidney is composed of an internal medullary and an external cortical substance.
The medullary substance (substantia medullaris) consists of a series of red-colored striated conical masses, termed the
renal pyramids, the bases of which are directed toward the circumference of the kidney, while their apices converge toward
the renal sinus, where they form prominent papillae projecting into the interior of the calyces.
The cortical substance (substantia corticalis) is reddish brown in color and soft and granular in consistence. It lies immediately beneath the fibrous tunic, arches over the bases of the pyramids, and dips in between adjacent pyramids toward the
renal sinus. The parts dipping in between the pyramids are named the renal columns (Bertini), while the portions which
connect the renal columns to each other and intervene between the bases of the pyramids and the fibrous tunic are called
the cortical arches. If the cortex be examined with a lens, it will be seen to consist of a series of lighter-colored, conical
areas, termed the radiate part, and a darker-colored intervening substance, which from the complexity of its structure is
named the convoluted part. The rays gradually taper toward the circumference of the kidney, and consist of a series of outward prolongations from the base of each renal pyramid.
Minute Anatomy. - The renal tubules, of which the kidney is for the most part made up, commence in the cortical substance, and after pursuing a very circuitous course through the cortical and medullary substances, finally end at the apices
of the renal pyramids by open mouths, so that the fluid which they contain is emptied, through the calyces, into the pelvis
of the kidney. If the surface of one of the papillae be examined with a lens, it will be seen to be studded over with minute
openings, the orifices of the renal tubules, from sixteen to twenty in number, and if pressure be made on a fresh kidney,
urine will be seen to exude from these orifices. The tubules commence in the convoluted part and renal columns as the renal corpuscles, which are small rounded masses of a deep red color, varying in size, but of an average of about 0.2 mm. in
diameter. Each of these little bodies is composed of two parts: a central glomerulus of vessels, and a membranous envelope,
the glomerular capsule (capsule of Bowman), which is the small pouch-like commencement of a renal tubule.
The glomerulus is a lobulated net-work of convoluted capillary bloodvessels, held together by scanty connective tissue.
This capillary net-work is derived from a small arterial twig, the afferent vessel, which enters the capsule, generally at a
point opposite to that at which the latter is connected with the tubule; and the resulting vein, the efferent vessel, emerges
from the capsule at the same point. The afferent vessel is usually the larger of the two. The glomerular or Bowman’s capsule, which surrounds the glomerulus, consists of a basement membrane, lined on its inner surface by a layer of flattened
epithelial cells, which are reflected from the lining membrane on to the glomerulus, at the point of entrance or exit of the
afferent and efferent vessels. The whole surface of the glomerulus is covered with a continuous layer of the same cells, on a
delicate supporting membrane. Thus between the glomerulus and the capsule a space is left, forming a cavity lined by a
continuous layer of squamous cells; this cavity varies in size according to the state of secretion and the amount of fluid present in it. In the fetus and young subject the lining epithelial cells are polyhedral or even columnar.
The renal tubules, commencing in the renal corpuscles, present, during their course, many changes in shape and direction,
and are contained partly in the medullary and partly in the cortical substance. At their junction with the glomerular capsule
they exhibit a somewhat constricted portion, which is termed the neck. Beyond this the tubule becomes convoluted, and
pursues a considerable course in the cortical substance constituting the proximal convoluted tube. After a time the convolutions disappear, and the tube approaches the medullary substance in a more or less spiral manner; this section of the tubule
has been called the spiral tube. Throughout this portion of their course the renal tubules are contained entirely in the cortical substance, and present a fairly uniform caliber. They now enter the medullary substance, suddenly become much smaller, quite straight in direction, and dip down for a variable depth into the pyramids, constituting the descending limb of Henle’s loop. Bending on themselves, they form what is termed the loop of Henle, and reascending, they become suddenly enlarged, forming the ascending limb of Henle’s loop, and reënter the cortical substance. This portion of the tubule ascends
for a short distance, when it again becomes dilated, irregular, and angular. This section is termed the zigzag tubule; it ends
in a convoluted tube, which resembles the proximal convoluted tubule, and is called the distal convoluted tubule. This
again terminates in a narrow junctional tube, which enters the straight or collecting tube.
The straight or collecting tubes commence in the radiate part of the cortex, where they receive the curved ends of the distal convoluted tubules. They unite at short intervals with one another, the resulting tubes presenting a considerable increase
in caliber, so that a series of comparatively large tubes passes from the bases of the rays into the renal pyramids. In the medulla the tubes of each pyramid converge to join a central tube (duct of Bellini) which finally opens on the summit of one
of the papillae; the contents of the tube are therefore discharged into one of the calyces.
The Renal Bloodvessels. - The kidney is plentifully supplied with blood by the renal artery, a large branch of the abdominal aorta. Before it enters the kidney, each artery divides into four or five branches which at the hilum lie mainly between the renal vein and ureter, the vein being in front, the ureter behind; one branch usually lies behind the ureter. Each
vessel gives off some small branches to the suprarenal glands, to the ureter, land to the surrounding cellular tissue and muscles. Frequently a second renal artery, termed the inferior renal, is given off from the abdominal aorta at a lower level, and
supplies the lower portion of the kidney, while occasionally an additional artery enters the upper part of the kidney. The
branches of the renal artery, while in the sinus, give off a few twigs for the nutrition of the surrounding tissues, and end in
the arteriae propriae renales, which enter the kidney proper in the renal columns. Two of these pass to each renal pyramid,
and run along its sides for its entire length, giving off in their course the afferent vessels of the renal corpuscles in the renal
columns. Having arrived at the bases of the pyramids, they form arterial arches or arcades which lie in the boundary zone
between the bases of the pyramids and the cortical arches, and break up into two distinct sets of branches devoted to the
supply of the remaining portions of the kidney.
The first set, the interlobular arteries, are given off at right angles from the side of the arterial arcade looking toward the
cortical substance, and pass directly outward between the medullary rays to reach the fibrous tunic, where they end in the
capillary net-work of this part. These vessels do not anastomose with each other, but form what are called end-arteries. In
their outward course they give off lateral branches; these are the afferent vessels for the renal corpuscles; they enter the
capsule, and end in the glomerulus. From each tuft the corresponding efferent vessel arises, and, having made its egress
from the capsule near to the point where the afferent vessel enters, breaks up into a number of branches, which form a
dense plexus around the adjacent urinary tubes.
The second set of branches from the arterial arcades supply the renal pyramids, which they enter at their bases; and, passing straight through their substance to their apices, terminate in the venous plexuses found in that situation. They are called
the arteriae rectae. The efferent vessels from the glomeruli nearest the medulla break up into leashes of straight vessels
(false arteriae rectae) which pass down into the medulla and join the plexus of vessels there
The renal veins arise from three sources, viz., the veins beneath the fibrous tunic, the plexuses around the convoluted tubules in the cortex, and the plexuses situated at the apices of the renal pyramids. The veins beneath the fibrous tunic (venae
stellatae) are stellate in arrangement, and are derived from the capillary net-work, into which the terminal branches of the
interlobular arteries break up. These join to form the interlobular veins, which pass inward between the rays, receive
branches from the plexuses around the convoluted tubules, and, having arrived at the bases of the renal pyramids, join with
the venae rectae, next to be described.
The venae rectae are branches from the plexuses at the apices of the medullary pyramids, formed by the terminations of
the arteriae rectae. They run outward in a straight course between the tubes of the medullary substance, and joining, as
above stated, the interlobular veins, form venous arcades; these in turn unite and form veins which pass along the sides of
the pyramids.
These vessels, venae propriae renales, accompany the arteries of the same name, running along the entire length of the
sides of the pyramids, and quit the kidney substance to enter the sinus. In this cavity they join the corresponding veins from
the other pyramids to form the renal vein, which emerges from the kidney at the hilum and opens into the inferior vena
cava; the left vein is longer than the right, and crosses in front of the abdominal aorta.
Variations. - Malformations of the kidney are not uncommon. There may be an entire absence of one kidney, but, according
to Morris, the number of these cases is “excessively small”: or there may be congenital atrophy of one kidney, when the
kidney is very small, but usually healthy in structure. These cases are of great importance, and must be duly taken into account when nephrectomy is contemplated. A more common malformation is where the two kidneys are fused together.
They may be joined together only at their lower ends by means of a thick mass of renal tissue, so as to form a horseshoeshaped body, or they may be completely united, forming a disk-like kidney, from which two ureters descend into the bladder. These fused kidneys are generally situated in the middle line of the abdomen, but may be misplaced as well. In some
mammals, e. g., ox and bear, the kidney consists of a number of distinct lobules; this lobulated condition is characteristic of
the kidney of the human fetus, and traces of it may persist in the adult. Sometimes the pelvis is duplicated, while a double
ureter is not very uncommon. In some rare instances a third kidney may be present.
One or both kidneys may be misplaced as a congenital condition, and remain fixed in this abnormal position. They are
then very often misshapen. They may be situated higher, though this is very uncommon, or lower than normal or removed
farther from the vertebral column than usual; or they may be displaced into the iliac fossa, over the sacroiliac joint, on to
the promontory of the sacrum, or into the pelvis between the rectum and bladder or by the side of the uterus. In these latter
cases they may give rise to very serious trouble. The kidney may also be misplaced as a congenital condition, but may not
be fixed; it is then known as a floating kidney. It is believed to be due to the fact that the kidney is completely enveloped by
peritoneum which then passes backward to the vertebral column as a double layer, forming a mesonephron which permits
movement. The kidney may also be misplaced as an acquired condition; in these cases the kidney is mobile in the tissues by
which it is surrounded, moving with the capsule in the perinephric tissues. This condition is known as movable kidney, and
is more common in the female than in the male. It occurs in badly nourished people, or in those who have become emaciated from any cause. It must not be confounded with the floating kidney, which is a congenital condition due to the development of a mesonephron. The two conditions cannot, however, be distinguished until the abdomen is opened or the kidney
explored from the loin.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 16. Structure, function and relations ureters, urinary bladder, urethra.
The aim: to learn the anatomy and relations of ureters, urinary bladder and urethra.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, nephrologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The Ureters
The ureters are the two tubes which convey the urine from the kidneys to the urinary bladder. Each commences within the
sinus of the corresponding kidney as a number of short cup-shaped tubes, termed calyces, which encircle the renal papillae.
Since a single calyx may enclose more than one papilla the calyces are generally fewer in number than the pyramids - the
former varying from seven to thirteen, the latter from eight to eighteen. The calyces join to form two or three short tubes,
and these unite to form a funnel-shaped dilatation, wide above and narrow below, named the renal pelvis, which is situated
partly inside and partly outside the renal sinus. It is usually placed on a level with the spinous process of the first lumbar
vertebra. 1
The Ureter Proper measures from 25 to 30 cm. in length, and is a thick-walled narrow cylindrical tube which is directly
continuous near the lower end of the kidney with the tapering extremity of the renal pelvis. It runs downward and medialward in front of the Psoas major and, entering the pelvic cavity, finally opens into the fundus of the bladder.
The abdominal part (pars abdominalis) lies behind the peritoneum on the medial part of the Psoas major, and is crossed
obliquely by the internal spermatic vessels. It enters the pelvic cavity by crossing either the termination of the common, or
the commencement of the external, iliac vessels.
At its origin the right ureter is usually covered by the descending part of the duodenum, and in its course downward lies to
the right of the inferior vena cava, and is crossed by the right colic and ileocolic vessels, while near the superior aperture of
the pelvis it passes behind the lower part of the mesentery and the terminal part of the ileum. The left ureter is crossed by
the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its mesentery.
The pelvic part (pars pelvina) runs at first downward on the lateral wall of the pelvic cavity, along the anterior border of
the greater sciatic notch and under cover of the peritoneum. It lies in front of the hypogastric artery medial to the obturator
nerve and the umbilical, obturator, inferior vesical, and middle hemorrhoidal arteries. Opposite the lower part of the greater
sciatic foramen it inclines medialward, and reaches the lateral angle of the bladder, where it is situated in front of the upper
end of the seminal vesicle and at a distance of about 5 cm. from the opposite ureter; here the ductus deferens crosses to its
medial side, and the vesical veins surround it. Finally, the ureters run obliquely for about 2 cm. through the wall of the
bladder and open by slit-like apertures into the cavity of the viscus at the lateral angles of the trigone. When the bladder is
distended the openings of the ureters are about 5 cm. apart, but when it is empty and contracted the distance between them
is diminished by one-half. Owing to their oblique course through the coats of the bladder, the upper and lower walls of the
terminal portions of the ureters become closely applied to each other when the viscus is distended, and, acting as valves,
prevent regurgitation of urine from the bladder.
In the female, the ureter forms, as it lies in relation to the wall of the pelvis, the posterior boundary of a shallow depression named the ovarian fossa, in which the ovary is situated. It then runs medialward and forward on the lateral aspect of
the cervix uteri and upper part of the vagina to reach the fundus of the bladder. In this part of its course it is accompanied
for about 2.5 cm. by the uterine artery, which then crosses in front of the ureter and ascends between the two layers of the
broad ligament. The ureter is distant about 2 cm. from the side of the cervix of the uterus. The ureter is sometimes duplicated on one or both sides, and the two tubes may remain distinct as far as the fundus of the bladder. On rare occasions they
open separately into the bladder cavity.
The fibrous coat (tunica adventitia) is continuous at one end with the fibrous tunic of the kidney on the floor of the sinus;
while at the other it is lost in the fibrous structure of the bladder.
In the renal pelvis the muscular coat (tunica muscularis) consists of two layers, longitudinal and circular: the longitudinal
fibers become lost upon the sides of the papillae at the extremities of the calyces; the circular fibers may be traced surrounding the medullary substance in the same situation. In the ureter proper the muscular fibers are very distinct, and are
arranged in three layers: an external longitudinal, a middle circular, and an internal, less distinct than the other two, but
having a general longitudinal direction. According to Kölliker this internal layer is found only in the neighborhood of the
bladder.
The mucous coat (tunica mucosa) is smooth, and presents a few longitudinal folds which become effaced by distension. It
is continuous with the mucous membrane of the bladder below, while it is prolonged over the papillae of the kidney above.
Its epithelium is of a transitional character, and resembles that found in the bladder. It consists of several layers of cells, of
which the innermost - that is to say, the cells in contact with the urine - are somewhat flattened, with concavities on their
deep surfaces into which the rounded ends of the cells of the second layer fit. These, the intermediate cells, more or less
resemble columnar epithelium, and are pear-shaped, with rounded internal extremities which fit into the concavities of the
cells of the first layer, and narrow external extremities which are wedged in between the cells of the third layer. The external or third layer consists of conical or oval cells varying in number in different parts, and presenting processes which extend down into the basement membrane. Beneath the epithelium, and separating it from the muscular coats, is a dense layer
of fibrous tissue containing many elastic fibers.
Variations. - The upper portion of the ureter is sometimes double; more rarely it is double the greater part of its extent, or
even completely so. In such cases there are two openings into the bladder. Asymmetry in these variations is common.
The urinary bladder is a musculomembranous sac which acts as a reservoir for the urine; and as its size, position, and relations vary according to the amount of fluid it contains, it is necessary to study it as it appears (a) when empty, and (b) when
distended.) In both conditions the position of the bladder varies with the condition of the rectum, being pushed upward and
forward when the rectum is distended.
The Empty Bladder. - When hardened in situ, the empty bladder has the form of a flattened tetrahedron, with its vertex tilted forward. It presents a fundus, a vertex, a superior and an inferior surface. The fundus is triangular in shape, and is directed downward and backward toward the rectum, from which it is separated by the rectovesical fascia, the vesiculae seminales, and the terminal portions of the ductus deferentes. The vertex is directed forward toward the upper part of the symphysis pubis, and from it the middle umbilical ligament is continued upward on the back of the anterior abdominal wall to
the umbilicus. The peritoneum is carried by it from the vertex of the bladder on to the abdominal wall to form the middle
umbilical fold. The superior surface is triangular, bounded on either side by a lateral border which separates it from the
inferior surface, and behind by a posterior border, represented by a line joining the two ureters, which intervenes between it
and the fundus. The lateral borders extend from the ureters to the vertex, and from them the peritoneum is carried to the
walls of the pelvis. On either side of the bladder the peritoneum shows a depression, named the paravesical fossa. The superior surface is directed upward, is covered by peritoneum, and is in relation with the sigmoid colon and some of the coils
of the small intestine. When the bladder is empty and firmly contracted, this surface is convex and the lateral and posterior
borders are rounded; whereas if the bladder be relaxed it is concave, and the interior of the viscus, as seen in a median sagittal section, presents the appearance of a V-shaped slit with a shorter posterior and a longer anterior limb - the apex of the
V corresponding with the internal orifice of the urethra. The inferior surface is directed downward and is uncovered by peritoneum. It may be divided into a posterior or prostatic area and two infero-lateral surfaces. The prostatic area is somewhat
triangular: it rests upon and is in direct continuity with the base of the prostate; and from it the urethra emerges. The inferolateral portions of the inferior surface are directed downward and lateralward: in front, they are separated from the symphysis pubis by a mass of fatty tissue which is named the retropubic pad; behind, they are in contact with the fascia which covers the Levatores ani and Obturatores interni.
When the bladder is empty it is placed entirely within the pelvis, below the level of the obliterated hypogastric arteries,
and below the level of those portions of the ductus deferentes which are in contact with the lateral wall of the pelvis; after
they cross the ureters the ductus deferentes come into contact with the fundus of the bladder. As the viscus fills, its fundus,
being more or less fixed, is only slightly depressed; while its superior surface gradually rises into the abdominal cavity,
carrying with it its peritoneal covering, and at the same time rounding off the posterior and lateral borders.
The Distended Bladder. - When the bladder is moderately full it contains about 0.5 liter and assumes an oval form; the long
diameter of the oval measures about 12 cm. and is directed upward and forward. In this condition it presents a posterosuperior, an antero-inferior, and two lateral surfaces, a fundus and a summit. The postero-superior surface is directed upward and backward, and is covered by peritoneum: behind, it is separated from the rectum by the rectovesical excavation,
while its anterior part is in contact with the coils of the small intestine. The antero-inferior surface is devoid of peritoneum,
and rests, below, against the pubic bones, above which it is in contact with the back of the anterior abdominal wall. The
lower parts of the lateral surfaces are destitute of peritoneum, and are in contact with the lateral walls of the pelvis. The line
of peritoneal reflection from the lateral surface is raised to the level of the obliterated hypogastric artery. The fundus undergoes little alteration in position, being only slightly lowered. It exhibits, however, a narrow triangular area, which is separated from the rectum merely by the rectovesical fascia. This area is bounded below by the prostate, above by the rectovesi-
cal fold of peritoneum, and laterally by the ductus deferentes. The ductus deferentes frequently come in contact with each
other above the prostate, and under such circumstances the lower part of the triangular area is obliterated. The line of reflection of the peritoneum from the rectum to the bladder appears to undergo little or no change when the latter is distended; it is situated about 10 cm. from the anus. The summit is directed upward and forward above the point of attachment of
the middle umbilical ligament, and hence the peritoneum which follows the ligament, forms a pouch of varying depth between the summit of the bladder, and the anterior abdominal wall.
The Bladder in the Child - In the newborn child the internal urethral orifice is at the level of the upper border of the symphysis pubis; the bladder therefore lies relatively at a much higher level in the infant than in the adult. Its anterior surface
“is in contact with about the lower two-thirds of that part of the abdominal wall which lies between the symphysis pubis
and the umbilicus”. Its fundus is clothed with peritoneum as far as the level of the internal orifice of the urethra. Although
the bladder of the infant is usually described as an abdominal organ, Symington has pointed out that only about one-half of
it lies above the plane of the superior aperture of the pelvis. Disse maintains that the internal urethral orifice sinks rapidly
during the first years, and then more slowly until the ninth year, after which it remains sta when it again slowly descends
and reaches its adult position.
The Female Bladder. - In the female, the bladder is in relation behind with the uterus and the upper part of the vagina. It is
separated from the anterior surface of the body of the uterus by the vesicouterine excavation, but below the level of this
excavation it is connected to the front of the cervix uteri and the upper part of the anterior wall of the vagina by areolar tissue. When the bladder is empty the uterus rests upon its superior surface. The female bladder is said by some to be more
capacious than that of the male, but probably the opposite is the case.
Ligaments. - The bladder is connected to the pelvic wall by the fascia endopelvina. In front this fascial attachment is
strengthened by a few muscular fibers, the Pubovesicales, which extend from the back of the pubic bones to the front of the
bladder; behind, other muscular fibers run from the fundus of the bladder to the sides of the rectum, in the sacrogenital
folds, and constitute the Rectovesicales.
The vertex of the bladder is joined to the umbilicus by the remains of the urachus which forms the middle umbilical ligament, a fibromuscular cord, broad at its attachment to the bladder but narrowing as it ascends.
From the superior surface of the bladder the peritoneum is carried off in a series of folds which are sometimes termed the
false ligaments of the bladder. Anteriorly there are three folds: the middle umbilical fold on the middle umbilical ligament,
and two lateral umbilical folds on the obliterated hypogastric arteries. The reflections of the peritoneum on to the side walls
of the pelvis form the lateral false ligaments, while the sacrogenital folds constitute posterior false ligaments.
Interior of the Bladder - The mucous membrane lining the bladder is, over the greater part of the viscus, loosely attached to
the muscular coat, and appears wrinkled or folded when the bladder is contracted: in the distended condition of the bladder
the folds are effaced. Over a small triangular area, termed the trigonum vesicae, immediately above and behind the internal
orifice of the urethra, the mucous membrane is firmly bound to the muscular coat, and is always smooth. The anterior angle
of the trigonum vesicae is formed by the internal orifice of the urethra: its postero-lateral angles by the orifices of the ureters. Stretching behind the latter openings is a slightly curved ridge, the torus uretericus, forming the base of the trigone and
produced by an underlying bundle of non-striped muscular fibers. The lateral parts of this ridge extend beyond the openings
of the ureters, and are named the plicae uretericae; they are produced by the terminal portions of the ureters as they traverse
obliquely the bladder wall. When the bladder is illuminated the torus uretericus appears as a pale band and forms an important guide during the operation of introducing a catheter into the ureter.
The orifices of the ureters are placed at the postero-lateral angles of the trigonum vesicae, and are usually slit-like in form.
In the contracted bladder they are about 2.5 cm. apart and about the same distance from the internal urethral orifice; in the
distended viscus these measurements may be increased to about 5 cm.
The internal urethral orifice is placed at the apex of the trigonum vesicae, in the most dependent part of the bladder, and is
usually somewhat crescentic in form; the mucous membrane immediately behind it presents a slight elevation, the uvula
vesicae, caused by the middle lobe of the prostate.
The serous coat (tunica serosa) is a partial one, and is derived from the peritoneum. It invests the superior surface and the
upper parts of the lateral surfaces, and is reflected from these on to the abdominal and pelvic walls.
The muscular coat (tunica muscularis) consists of three layers of unstriped muscular fibers: an external layer, composed of
fibers having for the most part a longitudinal arrangement; a middle layer, in which the fibers are arranged, more or less, in
a circular manner; and an internal layer, in which the fibers have a general longitudinal arrangement.
The fibers of the external layer arise from the posterior surface of the body of the pubis in both sexes (musculi pubovesicales), and in the male from the adjacent part of the prostate and its capsule. They pass, in a more or less longitudinal manner, up the inferior surface of the bladder, over its vertex, and then descend along its fundus to become attached to the prostate in the male, and to the front of the vagina in the female. At the sides of the bladder the fibers are arranged obliquely
and intersect one another. This layer has been named the Detrusor urinae muscle.
The fibers of the middle circular layer are very thinly and irregularly scattered on the body of the organ, and, although to
some extent placed transversely to the long axis of the bladder, are for the most part arranged obliquely. Toward the lower
part of the bladder, around the internal urethral orifice, they are disposed in a thick circular layer, forming the Sphincter
vesicae, which is continuous with the muscular fibers of the prostate.
The internal longitudinal layer is thin, and its fasciculi have a reticular arrangement, but with a tendency to assume for the
most part a longitudinal direction. Two bands of oblique fibers, originating behind the orifices of the ureters, converge to
the back part of the prostate, and are inserted by means of a fibrous process, into the middle lobe of that organ. They are the
muscles of the ureters, described by Sir C. Bell, who supposed that during the contraction of the bladder they serve to retain
the oblique direction of the ureters, and so prevent the reflux of the urine into them.
The submucous coat (tela submucosa) consists of a layer of areolar tissue, connecting together the muscular and mucous
coats, and intimately united to the latter.
The mucous coat (tunica mucosa) is thin, smooth, and of a pale rose color. It is continuous above through the ureters with
the lining membrane of the renal tubules, and below with that of the urethra. The loose texture of the submucous layer allows the mucous coat to be thrown into folds or rugae when the bladder is empty. Over the trigonum vesicae the mucous
membrane is closely attached to the muscular coat, and is not thrown into folds, but is smooth and flat. The epithelium covering it is of the transitional variety, consisting of a superficial layer of polyhedral flattened cells, each with one, two, or
three nuclei; beneath these is a stratum of large club-shaped cells, with their narrow extremities directed downward and
wedged in between smaller spindle-shaped cells, containing oval nuclei. The epithelium varies according as the bladder is
distended or contracted. In the former condition the superficial cells are flattened and those of the other layers are shortened; in the latter they present the appearance described above. There are no true glands in the mucous membrane of the
bladder, though certain mucous follicles which exist, especially near the neck of the bladder, have been regarded as such.
Abnormalities. - A defect of development, in which the bladder is implicated, is known under the name of extroversion of
the bladder. In this condition the lower part of the abdominal wall and the anterior wall of the bladder are wanting, so that
the fundus of the bladder presents on the abdominal surface, and is pushed forward by the pressure of the viscera within the
abdomen, forming a red vascular tumor on which the openings of the ureters are visible. The penis, except the glans, is rudimentary and is cleft on its dorsal surface, exposing the floor of the urethra, a condition known as epispadias. The pelvic
bones are also arrested in development.
The female urethra is a narrow membranous canal, about 4 cm. long, extending from the internal to the external urethral
orifice. It is placed behind the symphysis pubis, imbedded in the anterior wall of the vagina, and its direction is obliquely
downward and forward; it is slightly curved with the concavity directed forward. Its diameter when undilated is about 6
mm. It perforates the fasciae of the urogenital diaphragm, and its external orifice is situated directly in front of the vaginal
opening and about 2.5 cm. behind the glans clitoridis. The lining membrane is thrown into longitudinal folds, one of which,
placed along the floor of the canal, is termed the urethral crest. Many small urethral glands open into the urethra.
Structure. - The urethra consists of three coats: muscular, erectile, and mucous.
The muscular coat is continuous with that of the bladder; it extends the whole length of the tube, and consists of circular
fibers. In addition to this, between the superior and inferior fasciae of the urogenital diaphragm, the female urethra is surrounded by the Sphincter urethrae membranaceae, as in the male.
A thin layer of spongy erectile tissue, containing a plexus of large veins, intermixed with bundles of unstriped muscular
fibers, lies immediately beneath the mucous coat.
The mucous coat is pale; it is continuous externally with that of the vulva, and internally with that of the bladder. It is
lined by stratified squamous epithelium, which becomes transitional near the bladder. Its external orifice is surrounded by a
few mucous follicles.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 17. Structure, function and relations of male internal genital organs.
The aim: to learn the anatomy and relations of male internal genital organs.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, urologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The male genitals include the testes, the ductus deferentes, the vesiculae seminales, the ejaculatory ducts, and the penis,
together with the following accessory structures, viz., the prostate and the bulbourethral glands.
The Testes and their Coverings - The testes are two glandular organs, which secrete the semen; they are suspended in the
scrotum by the spermatic cords. At an early period of fetal life the testes are contained in the abdominal cavity, behind the
peritoneum. Before birth they descend to the inguinal canal, along which they pass with the spermatic cord, and, emerging
at the subcutaneous inguinal ring, they descend into the scrotum, becoming invested in their course by coverings derived
from the serous, muscular, and fibrous layers of the abdominal parietes, as well as by the scrotum.
The coverings of the testes are, the: Skin. Scrotum. Cremaster. Dartos tunic. Infundibuliform fascia. Intercrural fascia.
Tunica vaginalis.
The Scrotum is a cutaneous pouch which contains the testes and parts of the spermatic cords. It is divided on its surface
into two lateral portions by a ridge or raphé, which is continued forward to the under surface of the penis, and backward,
along the middle line of the perineum to the anus. Of these two lateral portions the left hangs lower than the right, to correspond with the greater length of the left spermatic cord. Its external aspect varies under different circumstances: thus, under
the influence of warmth, and in old and debilitated persons, it becomes elongated and flaccid; but, under the influence of
cold, and in the young and robust, it is short, corrugated, and closely applied to the testes.
The scrotum consists of two layers, the integument and the dartos tunic.
The Integument is very thin, of a brownish color, and generally thrown into folds or rugae. It is provided with sebaceous
follicles, the secretion of which has a peculiar odor, and is beset with thinly scattered, crisp hairs, the roots of which are
seen through the skin.
The Dartos Tunic (tunica dartos) is a thin layer of non-striped muscular fibers, continuous, around the base of the scrotum,
with the two layers of the superficial fascia of the groin and the perineum; it sends inward a septum, which divides the scrotal pouch into two cavities for the testes, and extends between the raphé and the under surface of the penis, as far as its root.
The dartos tunic is closely united to the skin externally, but connected with the subjacent parts by delicate areolar tissue,
upon which it glides with the greatest facility.
The Intercrural Fascia (intercolumnar or external spermatic fascia) is a thin membrane, prolonged downward around the
surface of the cord and testis. It is separated from the dartos tunic by loose areolar tissue.
The Cremaster consists of scattered bundles of muscular fibers connected together into a continuous covering by intermediate areolar tissue.
The Infundibuliform Fascia (tunica vaginalis communis [testis et funiculi spermatici]) is a thin layer, which loosely invests the cord; it is a continuation downward of the transversalis fascia.
The Tunica Vaginalis is described with the testes.
The Spermatic Cord (funiculus spermaticus) extends from the abdominal inguinal ring, where the structures of which it is
composed converge, to the back part of the testis. In the abdominal wall the cord passes obliquely along the inguinal canal,
lying at first beneath the Obliquus internus, and upon the fascia transversalis; but nearer the pubis, it rests upon the inguinal
and lacunar ligaments, having the aponeurosis of the Obliquus externus in front of it, and the inguinal falx behind it. It then
escapes at the subcutaneous ring, and descends nearly vertically into the scrotum. The left cord is rather longer than the
right, consequently the left testis hangs somewhat lower than its fellow.
Structure of the Spermatic Cord. - The spermatic cord is composed of arteries, veins, lymphatics, nerves, and the excretory
duct of the testis. These structures are connected together by areolar tissue, and invested by the layers brought down by the
testis in its descent.
The arteries of the cord are: the internal and external spermatics; and the artery to the ductus deferens.
The scrotum forms an admirable covering for the protection of the testes. These bodies, lying suspended and loose in the
cavity of the scrotum and surrounded by serous membrane, are capable of great mobility, and can therefore easily slip
about within the scrotum and thus avoid injuries from blows or squeezes. The skin of the scrotum is very elastic and capable of great distension, and on account of the looseness and amount of subcutaneous tissue, the scrotum becomes greatly
enlarged in cases of edema, to which this part is especially liable as a result of its dependent position.
The Testes are suspended in the scrotum by the spermatic cords, the left testis hanging somewhat lower than its fellow.
The average dimensions of the testis are from 4 to 5 cm. in length, 2.5 cm. in breadth, and 3 cm. in the antero-posterior diameter; its weight varies from 10.5 to 14 gm. Each testis is of an oval form, compressed laterally, and having an oblique
position in the scrotum; the upper extremity is directed forward and a little lateralward; the lower, backward and a little
medialward; the anterior convex border looks forward and downward, the posterior or straight border, to which the cord is
attached, backward and upward.
The anterior border and lateral surfaces, as well as both extremities of the organ, are convex, free, smooth, and invested by
the visceral layer of the tunica vaginalis. The posterior border, to which the cord is attached, receives only a partial investment from that membrane. Lying upon the lateral edge of this posterior border is a long, narrow, fiattened body, named the
epididymis.
The epididymis consists of a central portion or body; an upper enlarged extremity, the head (globus major); and a lower
pointed extremity, the tail (globus minor), which is continuous with the ductus deferens, the duct of the testis. The head is
intimately connected with the upper end of the testis by means of the efferent ductules of the gland; the tail is connected
with the lower end by cellular tissue, and a reflection of the tunica vaginalis. The lateral surface, head and tail of the epididymis are free and covered by the serous membrane; the body is also completely invested by it, excepting along its posterior border; while between the body and the testis is a pouch, named the sinus of the epididymis (digital fossa). The epididymis is connected to the back of the testis by a fold of the serous membrane.
Appendages of the Testis and Epididymis. - On the upper extremity of the testis, just beneath the head of the epididymis, is
a minute oval, sessile body, the appendix of the testis (hydatid of Morgagni); it is the remnant of the upper end of the Müllerian duct. On the head of the epididymis is a second small stalked appendage (sometimes duplicated); it is named the appendix of the epididymis (pedunculated hydatid), and is usually regarded as a detached efferent duct.
The testis is invested by three tunics: the tunica vaginalis, tunica albuginea, and tunica vasculosa.
The Tunica Vaginalis (tunica vaginalis propria testis) is the serous covering of the testis. It is a pouch of serous membrane, derived from the saccus vaginalis of the peritoneum, which in the fetus preceded the descent of the testis from the
abdomen into the scrotum. After its descent, that portion of the pouch which extends from the abdominal inguinal ring to
near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of
the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and
a parietal lamina.
The visceral lamina (lamina visceralis) covers the greater part of the testis and epididymis, connecting the latter to the
testis by means of a distinct fold. From the posterior border of the gland it is reflected on to the internal surface of the scrotum.
The parietal lamina (lamina parietalis) is far more extensive than the visceral, extending upward for some distance in front
and on the medial side of the cord, and reaching below the testis. The inner surface of the tunica vaginalis is smooth, and
covered by a layer of endothelial cells. The interval between the visceral and parietal laminae constitutes the cavity of the
tunica vaginalis.
The obliterated portion of the saccus vaginalis may generally be seen as a fibrocellular thread lying in the loose areolar
tissue around the spermatic cord; sometimes this may be traced as a distinct band from the upper end of the inguinal canal,
where it is connected with the peritoneum, down to the tunica vaginalis; sometimes it gradually becomes lost on the spermatic cord. Occasionally no trace of it can be detected. In some cases it happens that the pouch of peritoneum does not become obliterated, but the sac of the peritoneum communicates with the tunica vaginalis. This may give rise to one of the
varieties of oblique inguinal hernia. In other cases the pouch may contract, but not become entirely obliterated; it then
forms a minute canal leading from the peritoneum to the tunica vaginalis.
The Tunica Albuginea is the fibrous covering of the testis. It is a dense membrane, of a bluish-white color, composed of
bundles of white fibrous tissue which interlace in every direction. It is covered by the tunica vaginalis, except at the points
of attachment of the epididymis to the testis, and along its posterior border, where the spermatic vessels enter the gland. It
is applied to the tunica vasculosa over the glandular substance of the testis, and, at its posterior border, is reflected into the
interior of the gland, forming an incomplete vertical septum, called the mediastinum testis (corpus Highmori).
The mediastinum testis extends from the upper to near the lower extremity of the gland, and is wider above than below.
From its front and sides numerous imperfect septa (trabeculae) are given off, which radiate toward the surface of the organ,
and are attached to the tunica albuginea. They divide the interior of the organ into a number of incomplete spaces which are
somewhat cone-shaped, being broad at their bases at the surface of the gland, and becoming narrower as they converge to
the mediastinum. The mediastinum supports the vessels and duct of the testis in their passage to and from the substance of
the gland.
The Tunica Vasculosa is the vascular layer of the testis, consisting of a plexus of bloodvessels, held together by delicate
areolar tissue. It clothes the inner surface of the tunica albuginea and the different septa in the interior of the gland, and
therefore forms an internal investment to all the spaces of which the gland is composed.
Peculiarities. - The testis, developed in the lumbar region, may be arrested or delayed in its transit to the scrotum (cryptorchism). It may be retained in the abdomen; or it may be arrested at the abdominal inguinal ring, or in the inguinal canal; or
it may just pass out of the subcutaneous inguinal ring without finding its way to the bottom of the scrotum. When retained
in the abdomen it gives rise to no symptoms, other than the absence of the testis from the scrotum; but when it is retained in
the inguinal canal it is subjected to pressure and may become inflamed and painful. The retained testis is probably functionally useless; so that a man in whom both testes are retained (anorchism) is sterile, though he may not be impotent. The
absence of one testis is termed monorchism. When a testis is retained in the inguinal canal it is often complicated with a
congenital hernia, the funicular process of the peritoneum not being obliterated. In addition to the cases above described,
where there is some arrest in the descent of the testis, this organ may descend through the inguinal canal, but may miss the
scrotum and assume some abnormal position. The most common form is where the testis, emerging at the subcutaneous
inguinal ring, slips down between the scrotum and thigh and comes to rest in the perineum. This is known as perineal ectopia testis. With each variety of abnormality in the position of the testis, it is very common to find concurrently a congenital
hernia, or, if a hernia be not actually present, the funicular process is usually patent, and almost invariably so if the testis is
in the inguinal canal.
The testis, finally reaching the scrotum, may occupy an abnormal position in it. It may be inverted, so that its posterior or
attached border is directed forward and the tunica vaginalis is situated behind.
Fluid collections of a serous character are very frequently found in the scrotum. To these the term hydrocele is applied.
The most common form is the ordinary vaginal hydrocele, in which the fluid is contained in the sac of the tunica vaginalis,
which is separated, in its normal condition, from the peritoneal cavity by the whole extent of the inguinal canal. In another
form, the congenital hydrocele, the fluid is in the sac of the tunica vaginalis, but this cavity communicates with the general
peritoneal cavity, its tubular process remaining pervious. A third variety known as an infantile hydrocele, occurs in those
cases where the tubular process becomes obliterated only at its upper part, at or near the abdominal inguinal ring. It resembles the vaginal hydrocele, except as regards its shape, the collection of fluid extending up the cord into the inguinal canal.
Fourthly, the funicular process may become obliterated both at the abdominal inguinal ring and above the epididymis, leaving a central unobliterated portion, which may become distended with fluid, giving rise to a condition known as the encysted hydrocele of the cord.
The ductus deferens, the excretory duct of the testis, is the continuation of the canal of the epididymis. Commencing at the
lower part of the tail of the epididymis it is at first very tortuous, but gradually becoming less twisted it ascends along the
posterior border of the testis and medial side of the epididymis, and, as a constituent of the spermatic cord, traverses the
inguinal canal to the abdominal inguinal ring. Here it separates from the other structures of the cord. curves around the lateral side of the inferior epigastric artery, and ascends for about 2.5 cm. in front of the external iliac artery. It is next directed
backward and slightly downward, and, crossing the external iliac vessels obliquely, enters the pelvic cavity, where it lies
between the peritoneal membrane and the lateral wall of the pelvis, and descends on the medial side of the obliterated um-
bilical artery and the obturator nerve and vessels. It then crosses in front of the ureter, and, reaching the medial side of this
tube, bends to form an acute angle, and runs medialward and slightly forward between the fundus of the bladder and the
upper end of the seminal vesicle. Reaching the medial side of the seminal vesicle, it is directed downward and medialward
in contact with it, gradually approaching the opposite ductus. Here it lies between the fundus of the bladder and the rectum,
where it is enclosed, together with the seminal vesicle, in a sheath derived from the rectovesical portion of the fascia endopelvina. Lastly, it is directed downward to the base of the prostate, where it becomes greatly narrowed, and is joined at
an acute angle by the duct of the seminal vesicle to form the ejaculatory duct, which traverses the prostate behind its middle
lobe and opens into the prostatic portion of the urethra, close to the orifice of the prostatic utricle. The ductus deferens presents a hard and cord-like sensation to the fingers, and is of cylindrical form; its walls are dense, and its canal is extremely
small. At the fundus of the bladder it becomes enlarged and tortuous, and this portion is termed the ampulla. A small triangular area of the fundus of the bladder, between the ductus deferentes laterally and the bottom of the rectovesical excavation of peritoneum above, is in contact with the rectum.
Ductuli Aberrantes. - A long narrow tube, the ductulus aberrans inferior (vas aberrans of Haller), is occasionally found
connected with the lower part of the canal of the epididymis, or with the commencement of the ductus deferens. Its length
varies from 3.5 to 35 cm., and it may become dilated toward its extremity; more commonly it retains the same diameter
throughout. Its structure is similar to that of the ductus deferens. Occasionally it is found unconnected with the epididymis.
A second tube, the ductulus aberrans superior, occurs in the head of the epididymis; it is connected with the rete testis.
Paradidymis (organ of Giraldés). - This term is applied to a small collection of convoluted tubules, situated in front of the
lower part of the cord above the head of the epididymis. These tubes are lined with columnar ciliated epithelium, and probably represent the remains of a part of the Wolffian body.
Structure. - The ductus deferens consists of three coats: (1) an external or areolar coat; (2) a muscular coat which in the
greater part of the tube consists of two layers of unstriped muscular fiber: an outer, longitudinal in direction, and an inner,
circular; but in addition to these, at the commencement of the ductus, there is a third layer, consisting of longitudinal fibers,
placed internal to the circular stratum, between it and the mucous membrane; (3) an internal or mucous coat, which is pale,
and arranged in longitudinal folds. The mucous coat is lined by columnar epithelium which is non-ciliated throughout the
greater part of the tube; a variable portion of the testicular end of the tube is lined by two strata of columnar cells and the
cells of the superficial layer are ciliated
The vesiculae seminales are two lobulated membranous pouches, placed between the fundus of the bladder and the rectum, serving as reservoirs for the semen, and secreting a fluid to be added to the secretion of the testes. Each sac is somewhat pyramidal in form, the broad end being directed backward, upward and lateralward. It is usually about 7.5 cm. long,
but varies in size, not only in different individuals, but also in the same individual on the two sides. The anterior surface is
in contact with the fundus of the bladder, extending from near the termination of the ureter to the base of the prostate. The
posterior surface rests upon the rectum, from which it is separated by the rectovesical fascia. The upper extremities of the
two vesicles diverge from each other, and are in relation with the ductus deferentes and the terminations of the ureters, and
are partly covered by peritoneum. The lower extremities are pointed, and converge toward the base of the prostate, where
each joins with the corresponding ductus deferens to form the ejaculatory duct. Along the medial margin of each vesicle
runs the ampulla of the ductus deferens.
Each vesicle consists of a single tube, coiled upon itself, and giving off several irregular cecal diverticula; the separate
coils, as well as the diverticula, are connected together by fibrous tissue. When uncoiled, the tube is about the diameter of a
quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac; its anterior extremity becomes constricted
into a narrow straight duct, which joins with the corresponding ductus deferens to form the ejaculatory duct.
Structure. - The vesiculae seminales are composed of three coats: an external or areolar coat; a middle or muscular coat
thinner than in the ductus deferens and arranged in two layers, an outer longitudinal and inner circular; an internal or mucous coat, which is pale, of a whitish brown color, and presents a delicate reticular structure. The epithelium is columnar,
and in the diverticula goblet cells are present, the secretion of which increases the bulk of the seminal fluid.
The ejaculatory ducts are two in number, one on either side of the middle line. Each is formed by the union of the duct
from the vesicula seminalis with the ductus deferens, and is about 2 cm. long. They commence at the base of the prostate,
and run forward and downward between its middle and lateral lobes, and along the sides of the prostatic utricle, to end by
separate slit-like orifices close to or just within the margins of the utricle. The ducts diminish in size, and also converge,
toward their terminations.
Structure. - The coats of the ejaculatory ducts are extremely thin. They are: an outer fibrous layer, which is almost entirely
lost after the entrance of the ducts into the prostate; a layer of muscular fibers consisting of a thin outer circular, and an
inner longitudinal, layer; and mucous membrane.
The prostate is a firm, partly glandular and partly muscular body, which is placed immediately below the internal urethral
orifice and around the commencement of the urethra. It is situated in the pelvic cavity, below the lower part of the symphysis pubis, above the superior fascia of the urogenital diaphragm, and in front of the rectum, through which it may be distinctly felt, especially when enlarged. It is about the size of a chestnut and somewhat conical in shape, and presents for examination a base, an apex, an anterior, a posterior and two lateral surfaces.
The base (basis prostatae) is directed upward, and is applied to the inferior surface of the bladder, The greater part of this
surface is directly continuous with the bladder wall; the urethra penetrates it nearer its anterior than its posterior border.
The apex (apex prostatae) is directed downward, and is in contact with the superior fascia of the urogenital diaphragm.
Surfaces. - The posterior surface (facies posterior) is flattened from side to side and slightly convex from above downward;
it is separated from the rectum by its sheath and some loose connective tissue, and is distant about 4 cm. from the anus.
Near its upper border there is a depression through which the two ejaculatory ducts enter the prostate. This depression
serves to divide the posterior surface into a lower larger and an upper smaller part. The upper smaller part constitutes the
middle lobe of the prostate and intervenes between the ejaculatory ducts and the urethra; it varies greatly in size, and in
some cases is destitute of glandular tissue. The lower larger portion sometimes presents a shallow median furrow, which
imperfectly separates it into a right and a left lateral lobe: these form the main mass of the gland and are directly continuous
with each other behind the urethra. In front of the urethra they are connected by a band which is named the isthmus: this
consists of the same tissues as the capsule and is devoid of glandular substance.
The anterior surface (facies anterior) measures about 2.5 cm. from above downward but is narrow and convex from side to
side. It is placed about 2 cm. behind the pubic symphysis, from which it is separated by a plexus of veins and a quantity of
loose fat. It is connected to the pubic bone on either side by the puboprostatic ligaments. The urethra emerges from this
surface a little above and in front of the apex of the gland.
The lateral surfaces are prominent, and are covered by the anterior portions of the Levatores ani, which are, however, separated from the gland by a plexus of veins.
The prostate measures about 4 cm. transversely at the base, 2 cm. in its antero-posterior diameter, and 3 cm. in its vertical
diameter. Its weight is about 8 gm. It is held in its position by the puboprostatic ligaments; by the superior fascia of the
urogenital diaphragm, which invests the prostate and the commencement of the membranous portion of the urethra; and by
the anterior portions of the Levatores ani, which pass backward from the pubis and embrace the sides of the prostate. These
portions of the Levatores ani, from the support they afford to the prostate, are named the Levatores prostatae.
The prostate is perforated by the urethra and the ejaculatory ducts. The urethra usually lies along the junction of its anterior with its middle third. The ejaculatory ducts pass obliquely downward and forward through the posterior part of the prostate, and open into the prostatic portion of the urethra.
Structure. - The prostate is immediately enveloped by a thin but firm fibrous capsule, distinct from that derived from the
fascia endopelvina, and separated from it by a plexus of veins. This capsule is firmly adherent to the prostate and is structurally continuous with the stroma of the gland, being composed of the same tissues, viz.: non-striped muscle and fibrous
tissue. The substance of the prostate is of a pale reddish-gray color, of great density, and not easily torn. It consists of glandular substance and muscular tissue.
The bulbourethral glands are two small, rounded, and somewhat lobulated bodies, of a yellow color, about the size of
peas, placed behind and lateral to the membranous portion of the urethra, between the two layers of the fascia of the urogenital diaphragm. They lie close above the bulb, and are enclosed by the transverse fibers of the Sphincter urethrae membranaceae. Their existence is said to be constant: they gradually diminish in size as age advances.
The excretory duct of each gland, nearly 2.5 cm. long, passes obliquely forward beneath the mucous membrane, and
opens by a minute orifice on the floor of the cavernous portion of the urethra about 2.5 cm. in front of the urogenital diaphragm.
Structure. - Each gland is made up of several lobules, held together by a fibrous investment. Each lobule consists of a number of acini, lined by columnar epithelial cells, opening into one duct, which joins with the ducts of other lobules outside
the gland to form the single excretory duct.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 18. Structure, function and relations of male external genital organs.
The aim: to learn the anatomy and relations of male external genital organs.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, urologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The penis is a pendulous organ suspended from the front and sides of the pubic arch and containing the greater part of the
urethra. In the flaccid condition it is cylindrical in shape, but when erect assumes the form of a triangular prism with rounded angles, one side of the prism forming the dorsum. It is composed of three cylindrical masses of cavernous tissue bound
together by fibrous tissue and covered with skin. Two of the masses are lateral, and are known as the corpora cavernosa
penis; the third is median, and is termed the corpus cavernosum urethrae
The Corpora Cavernosa Penis form the greater part of the substance of the penis. For their anterior three-fourths they lie in
intimate apposition with one another, but behind they diverge in the form of two tapering processes, known as the crura,
which are firmly connected to the rami of the pubic arch. Traced from behind forward, each crus begins by a blunt-pointed
process in front of the tuberosity of the ischium. Just before it meets its fellow it presents a slight enlargement, named by
Kobelt the bulb of the corpus cavernosum penis. Beyond this point the crus undergoes a constriction and merges into the
corpus cavernosum proper, which retains a uniform diameter to its anterior end. Each corpus cavernosum penis ends abruptly in a rounded extremity some distance from the point of the penis.
The corpora cavernosa penis are surrounded by a strong fibrous envelope consisting of superficial and deep fibers. The
superficial fibers are longitudinal in direction, and form a single tube which encloses both corpora; the deep fibers are arranged circularly around each corpus, and form by their junction in the median plane the septum of the penis. This is thick
and complete behind, but is imperfect in front, where it consists of a series of vertical bands arranged like the teeth of a
comb; it is therefore named the septum pectiniforme.
The Corpus Cavernosum Urethrae (corpus spongiosum) contains the urethra. Behind, it is expanded to form the urethral
bulb, and lies in apposition with the inferior fascia of the urogenital diaphragm, from which it receives a fibrous investment. The urethra enters the bulb nearer to the upper than to the lower surface. On the latter there is a median sulcus, from
which a thin fibrous septum projects into the substance of the bulb and divides it imperfectly into two lateral lobes or hemispheres.
The portion of the corpus cavernosum urethrae in front of the bulb lies in a groove on the under surface of the conjoined
corpora cavernosa penis. It is cylindrical in form and tapers slightly from behind forward. Its anterior end is expanded in
the form of an obtuse cone, flattened from above downward. This expansion, termed the glans penis, is moulded on the
rounded ends of the corpora cavernosa penis, extending farther on their upper than on their lower surfaces. At the summit
of the glans is the slit-like vertical external urethral orifice. The circumference of the base of the glans forms a rounded
projecting border, the corona glandis, overhanging a deep retroglandular sulcus, behind which is the neck of the penis.
For descriptive purposes it is convenient to divide the penis into three regions: the root, the body, and the extremity.
The root (radix penis) of the penis is triradiate in form, consisting of the diverging crura, one on either side, and the median urethral bulb. Each crus is covered by the Ischiocavernosus, while the bulb is surrounded by the Bulbocavernosus. The
root of the penis lies in the perineum between the inferior fascia of the urogenital diaphragm and the fascia of Colles. In
addition to being attached to the fasciae and the pubic rami, it is bound to the front of the symphysis pubis by the fundiform
and suspensory ligaments. The fundiform ligament springs from the front of the sheath of the Rectus abdominis and the
linea alba; it splits into two fasciculi which encircle the root of the penis. The upper fibers of the suspensory ligament pass
downward from the lower end of the linea alba, and the lower fibers from the symphysis pubis; together they form a strong
fibrous band, which extends to the upper surface of the root, where it blends with the fascial sheath of the organ.
The body (corpus penis) extends from the root to the ends of the corpora cavernosa penis, and in it these corpora cavernosa are intimately bound to one another. A shallow groove which marks their junction on the upper surface lodges the deep
dorsal vein of the penis, while a deeper and wider groove between them on the under surface contains the corpus cavernosum urethrae. The body is ensheathed by fascia, which is continuous above with the fascia of Scarpa, and below with the
dartos tunic of the scrotum and the fascia of Colles.
The extremity is formed by the glans penis, the expanded anterior end of the corpus cavernosum urethrae. It is separated
from the body by the constricted neck, which is overhung by the corona glandis.
The integument covering the penis is remarkable for its thinness, its dark color, its looseness of connection with the deeper parts of the organ, and its absence of adipose tissue. At the root of the penis it is continuous with that over the pubes,
scrotum, and perineum. At the neck it leaves the surface and becomes folded upon itself to form the prepuce or foreskin.
The internal layer of the prepuce is directly continuous, along the line of the neck, with the integument over the glans. Immediately behind the external urethral orifice it forms a small secondary reduplication, attached along the bottom of a depressed median raphé, which extends from the meatus to the neck; this fold is termed the frenulum of the prepuce. The integument covering the glans is continuous with the urethral mucous membrane at the orifice; it is devoid of haris, but projecting from its free surface are a number of small, highly sensitive papillae. Scattered glands on the corona, neck, glans
and inner layer of the prepuce, the preputial glands, have been described. They secrete a sebaceous material of very peculiar odor, which probably contains casein, and readily undergoes decomposition; when mixed with discarded epithelial cells
it is called smegma.
The prepuce covers a variable amount of the glans, and is separated from it by a potential sac - the preputial sac - which
presents two shallow fossae, one on either side of the frenulum.
Structure of the Penis. - From the internal surface of the fibrous envelope of the corpora cavernosa penis, as well as from
the sides of the septum, numerous bands or cords are given off, which cross the interior of these corpora cavernosa in all
directions, subdividing them into a number of separate compartments, and giving the entire structure a spongy appearance.
These bands and cords are called trabeculae, and consist of white fibrous tissue, elastic fibers, and plain muscular fibers. In
them are contained numerous arteries and nerves. The component fibers which form the trabeculae are larger and stronger
around the circumference than at the centers of the corpora cavernosa; they are also thicker behind than in front. The interspaces (cavernous spaces), on the contrary, are larger at the center than at the circumference, their long diameters being
directed transversely. They are filled with blood, and are lined by a layer of flattened cells similar to the endothelial lining
of veins.
The fibrous envelope of the corpus cavernosum urethrae is thinner, whiter in color, and more elastic than that of the corpora cavernosa penis. The trabeculae are more delicate, nearly uniform in size, and the meshes between them smaller than
in the corpora cavernosa penis: their long diameters, for the most part, corresponding with that of the penis. The external
envelope or outer coat of the corpus cavernosum urethrae is formed partly of unstriped muscular fibers, and a layer of the
same tissue immediately surrounds the canal of the urethra.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 19. Structure, function and relations of female internal genital organs.
The aim: to learn the anatomy and relations of ureters, urinary bladder and urethra.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, nephrologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The female genital organs consist of an internal and an external group. The internal organs are situated within the pelvis,
and consist of the ovaries, the uterine tubes, the uterus, and the vagina. The external organs are placed below the urogenital
diaphragm and below and in front of the pubic arch. They comprise the mons pubis, the labia majora et minora pudendi, the
clitoris, the bulbus vestibuli, and the greater vestibular glands.
The ovaries are homologous with the testes in the male. They are two nodular bodies, situated one on either side of the
uterus in relation to the lateral wall of the pelvis, and attached to the back of the broad ligament of the uterus, behind and
below the uterine tubes. The ovaries are of a grayish-pink color, and present either a smooth or a puckered uneven surface.
They are each about 4 cm. in length, 2 cm. in width, and about 8 mm. in thickness, and weigh from 2 to 3.5 gm. Each ovary
presents a lateral and a medial surface, an upper or tubal and a lower or uterine extremity, and an anterior or mesovarion
and a posterior free border. It lies in a shallow depression, named the ovarian fossa, on the lateral wall of the pelvis; this
fossa is bounded above by the external iliac vessels, in front by the obliterated umbilical artery, and behind by the ureter.
The exact position of the ovary has been the subject of considerable difference of opinion, and the description here given
applies to the ovary of the nulliparous woman. The ovary becomes displaced during the first pregnancy, and probably never
again returns to its original position. In the erect posture the long axis of the ovary is vertical. The tubal extremity is near
the external iliac vein; to it are attached the ovarian fimbria of the uterine tube and a fold of peritoneum, the suspensory
ligament of the ovary, which is directed upward over the iliac vessels and contains the ovarian vessels. The uterine end is
directed downward toward the pelvic floor, it is usually narrower than the tubal, and is attached to the lateral angle of the
uterus, immediately behind the uterine tube, by a rounded cord termed the ligament of the ovary, which lies within the
broad ligament and contains some non-striped, muscular fibers. The lateral surface is in contact with the parietal peritoneum, which lines the ovarian fossa; the medial surface is to a large extent covered by the fimbriated extremity of the uterine
tube. The mesovarian border is straight and is directed toward the obliterated umbilical artery, and is attached to the back of
the broad ligament by a short fold named the mesovarium. Between the two layers of this fold the bloodvessels and nerves
pass to reach the hilum of the ovary. The free border is convex, and is directed toward the ureter. The uterine tube arches
over the ovary, running upward in relation to its mesovarian border, then curving over its tubal pole, and finally passing
downward on its free border and medial surface.
Epoöphoron (parovarium; organ of Rosenmüller) - The epoöphoron lies in the mesosalpinx between the ovary and the uterine tube, and consists of a few short tubules (ductuli transversi) which converge toward the ovary while their opposite ends
open into a rudimentary duct, the ductus longitudinalis epoöphori (duct of Gärtner).
Paroöphoron. - The paroöphoron consists of a few scattered rudimentary tubules, best seen in the child, situated in the
broad ligament between the epoöphoron and the uterus.
The ductuli transversi of the epoophoron and the tubules of the paroophoron are remnants of the tubules of the Wolffian
body or mesonephros; the ductus longitudinalis epoöphori is a persistent portion of the Wolffian duct.
In the fetus the ovaries are situated, like the testes, in the lumbar region, near the kidneys, but they gradually descend into
the pelvis
Structure - The surface of the ovary is covered by a layer of columnar cells which constitutes the germinal epithelium of
Waldeyer. This epithelium gives to the ovary a dull gray color as compared with the shining smoothness of the peritoneum;
and the transition between the squamous epithelium of the peritoneum and the columnar cells which cover the ovary is usually marked by a line around the anterior border of the ovary. The ovary consists of a number of vesicular ovarian follicles
imbedded in the meshes of a stroma or frame-work.
The stroma is a peculiar soft tissue, abundantly supplied with bloodvessels, consisting for the most part of spindle-shaped
cells with a small amount of ordinary connective tissue. These cells have been regarded by some anatomists as unstriped
muscle cells, which, indeed, they most resemble; by others as connective-tissue cells. On the surface of the organ this tissue
is much condensed, and forms a layer (tunica albuginea) composed of short connective-tissue fibers, with fusiform cells
between them. The stroma of the ovary may contain interstitial cells resembling those of the testis.
The development and maturation of the follicles and ova continue uninterruptedly from puberty to the end of the fruitful
period of woman’s life, while their formation commences before birth. Before puberty the ovaries are small and the follicles contained in them are disposed in a comparatively thick layer in the cortical substance; here they present the appear-
ance of a large number of minute closed vesicles, constituting the early condition of the follicles; many, however, never
attain full development, but shrink and disappear. At puberty the ovaries enlarge and become more vascular, the follicles
are developed in greater abundance, and their ova are capable of fecundation.
Discharge of the Ovum. - The follicles, after attaining a certain stage of development, gradually approach the surface of the
ovary and burst; the ovum and fluid contents of the follicle are liberated on the exterior of the ovary, and carried into the
uterine tube by currents set up by the movements of the cilia covering the mucous membrane of the fimbriae.
Corpus Luteum. - After the discharge of the ovum the lining of the follicle is thrown into folds, and vascular processes
grow inward from the surrounding tissue. In this way the space is filled up and the corpus luteum formed. It consists at first
of a radial arrangement of yellow cells with bloodvessels and lymphatic spaces, and later it merges with the surrounding
stroma.
The uterine tubes convey the ova from the ovaries to the cavity of the uterus. They are two in number, one on either side,
situated in the upper margin of the broad ligament, and extending from the superior angle of the uterus to the side of the
pelvis. Each tube is about 10 cm. long, and is described as consisting of three portions: (1) the isthmus, or medial constricted third; (2) the ampulla, or intermediate dilated portion, which curves over the ovary; and (3) the infundibulum with its
abdominal ostium, surrounded by fimbriae, one of which, the ovarian fimbria is attached to the ovary. The uterine tube is
directed lateralward as far as the uterine pole of the ovary, and then ascends along the mesovarian border of the ovary to the
tubal pole, over which it arches; finally it turns downward and ends in relation to the free border and medial surface of the
ovary. The uterine opening is minute, and will only admit a fine bristle; the abdominal opening is somewhat larger. In connection with the fimbriae of the uterine tube, or with the broad ligament close to them, there are frequently one or more
small pedunculated vesicles. These are termed the appendices vesiculosae (hydatids of Morgagni).
The uterine tube consists of three coats: serous, muscular, and mucous. The external or serous coat is peritoneal. The middle or muscular coat consists of an external longitudinal and an internal circular layer of non-striped muscular fibers continuous with those of the uterus. The internal or mucous coat is continuous with the mucous lining of the uterus, and, at the
abdominal ostium of the tube, with the peritoneum. It is thrown into longitudinal folds, which in the ampulla are much
more extensive than in the isthmus. The lining epithelium is columnar and ciliated. This form of epithelium is also found on
the inner surface of the fimbriae. while on the outer or serous surfaces of these processes the epithelium gradually merges
into the endothelium of the peritoneum.
Fertilization of the ovum is believed to occur in the tube, and the fertilized ovum is then normally passed on into the uterus; the ovum, however, may adhere to and undergo development in the uterine tube, giving rise to the commonest variety
of ectopic gestation. In such cases the amnion and chorion are formed, but a true decidua is never present; and the gestation
usually ends by extrusion of the ovum through the abdominal ostium, although it is not uncommon for the tube to rupture
into the peritoneal cavity, this being accompanied by severe hemorrhage, and needing surgical interference.
The uterus is a hollow, thick-walled, muscular organ situated deeply in the pelvic cavity between the bladder and rectum.
Into its upper part the uterine tubes open, one on either side, while below, its cavity communicates with that of the vagina.
When the ova are discharged from the ovaries they are carried to the uterine cavity through the uterine tubes. If an ovum be
fertilized it imbeds itself in the uterine wall and is normally retained in the uterus until prenatal development is completed,
the uterus undergoing changes in size and structure to accommodate itself to the needs of the growing embryo. After parturition the uterus returns almost to its former condition, but certain traces of its enlargement remains. It is necessary, therefore, to describe as the type-form the adult virgin uterus, and then to consider the modifications which are effected as a result of pregnancy.
In the virgin state the uterus is flattened antero-posteriorly and is pyriform in shape, with the apex directed downward and
backward. It lies between the bladder in front and the pelvic or sigmoid colon and rectum behind, and is completely within
the pelvis, so that its base is below the level of the superior pelvic aperture. Its upper part is suspended by the broad and the
round ligaments, while its lower portion is imbedded in the fibrous tissue of the pelvis.
The long axis of the uterus usually lies approximately in the axis of the superior pelvic aperture, but as the organ is freely
movable its position varies with the state of distension of the bladder and rectum. Except when much displaced by a fully
distended bladder, it forms a forward angle with the vagina, since the axis of the vagina corresponds to the axes of the cavity and inferior aperture of the pelvis.
The uterus measures about 7.5 cm. in length, 5 cm. in breadth, at its upper part, and nearly 2.5 cm. in thickness; it weighs
from 30 to 40 gm. It is divisible into two portions. On the surface, about midway between the apex and base, is a slight
constriction, known as the isthmus, and corresponding to this in the interior is a narrowing of the uterine cavity, the internal
orifice of the uterus. The portion above the isthmus is termed the body, and that below, the cervix. The part of the body
which lies above a plane passing through the points of entrance of the uterine tubes is known as the fundus.
Body (corpus uteri). - The body gradually narrows from the fundus to the isthmus.
The vesical or anterior surface (facies vesicalis) is flattened and covered by peritoneum, which is reflected on to the bladder to form the vesicouterine excavation. The surface lies in apposition with the bladder.
The intestinal or posterior surface (facies intestinalis) is convex transversely and is covered by peritoneum, which is continued down on to the cervix and vagina. It is in relation with the sigmoid colon, from which it is usually separated by some
coils of small intestine.
The fundus (fundus uteri) is convex in all directions, and covered by peritoneum continuous with that on the vesical and
intestinal surfaces. On it rest some coils of small intestine, and occasionally the distended sigmoid colon.
The lateral margins (margo lateralis) are slightly convex. At the upper end of each the uterine tube pierces the uterine
wall. Below and in front of this point the round ligament of the uterus is fixed, while behind it is the attachment of the lig-
ament of the ovary. These three structures lie within a fold of peritoneum which is reflected from the margin of the uterus
to the wall of the pelvis, and is named the broad ligament.
Cervix (cervix uteri; neck). - The cervix is the lower constricted segment of the uterus. It is somewhat conical in shape,
with its truncated apex directed downward and backward, but is slightly wider in the middle than either above or below.
Owing to its relationships, it is less freely movable than the body, so that the latter may bend on it. The long axis of the
cervix is therefore seldom in the same straight line as the long axis of the body. The long axis of the uterus as a whole presents the form of a curved line with its concavity forward, or in extreme cases may present an angular bend at the region of
the isthmus.
The cervix projects through the anterior wall of the vagina, which divides it into an upper, supravaginal portion, and a
lower, vaginal portion.
The supravaginal portion (portio supravaginalis [cervicis]) is separated in front from the bladder by fibrous tissue (parametrium), which extends also on to its sides and lateralward between the layers of the broad ligaments. The uterine arteries
reach the margins of the cervix in this fibrous tissue, while on either side the ureter runs downward and forward in it at a
distance of about 2 cm. from the cervix. Posteriorly, the supravaginal cervix is covered by peritoneum, which is prolonged
below on to the posterior vaginal wall, when it is reflected on to the rectum, forming the rectouterine excavation. It is in
relation with the rectum, from which it may be separated by coils of small intestine.
The vaginal portion (portio vaginalis [cervicis]) of the cervix projects free into the anterior wall of the vagina between the
anterior and posterior fornices. On its rounded extremity is a small, depressed, somewhat circular aperture, the external
orifice of the uterus, through which the cavity of the cervix communicates with that of the vagina. The external orifice is
bounded by two lips, an anterior and a posterior, of which the anterior is the shorter and thicker, although, on account of the
slope of the cervix, it projects lower than the posterior. Normally, both lips are in contact with the posterior vaginal wall.
Interior of the Uterus - The cavity of the uterus is small in comparison with the size of the organ.
The Cavity of the Body (cavum uteri) is a mere slit, flattened antero-posteriorly. It is triangular in shape, the base being
formed by the internal surface of the fundus between the orifices of the uterine tubes, the apex by the internal orifice of the
uterus through which the cavity of the body communicates with the canal of the cervix.
The Canal of the Cervix (canalis cervicis uteri) is somewhat fusiform, flattened from before backward, and broader at the
middle than at either extremity. It communicates above through the internal orifice with the cavity of the body, and below
through the external orifice with the vaginal cavity. The wall of the canal presents an anterior and a posterior longitudinal
ridge, from each of which proceed a number of small oblique columns, the palmate folds, giving the appearance of branches from the stem of a tree; to this arrangement the name arbor vitae uterina is applied. The folds on the two walls are not
exactly opposed, but fit between one another so as to close the cervical canal.
The total length of the uterine cavity from the external orifice to the fundus is about 6.25 cm.
Ligaments. - The ligaments of the uterus are eight in number: one anterior; one posterior; two lateral or broad; two uterosacral; and two round ligaments.
The anterior ligament consists of the vesicouterine fold of peritoneum, which is reflected on to the bladder from the front
of the uterus, at the junction of the cervix and body.
The posterior ligament consists of the rectovaginal fold of peritoneum, which is reflected from the back of the posterior
fornix of the vagina on to the front of the rectum. It forms the bottom of a deep pouch called the rectouterine excavation,
which is bounded in front by the posterior wall of the uterus, the supravaginal cervix, and the posterior fornix of the vagina;
behind, by the rectum; and laterally by two crescentic folds of peritoneum which pass backward from the cervix uteri on
either side of the rectum to the posterior wall of the pelvis. These folds are named the sacrogenital or rectouterine folds.
They contain a considerable amount of fibrous tissue and non-striped muscular fibers which are attached to the front of the
sacrum and constitute the uterosacral ligaments.
The two lateral or broad ligaments (ligamentum latum uteri) pass from the sides of the uterus to the lateral walls of the
pelvis. Together with the uterus they form a septum across the female pelvis, dividing that cavity into two portions. In the
anterior part is contained the bladder; in the posterior part the rectum, and in certain conditions some coils of the small intestine and a part of the sigmoid colon. Between the two layers of each broad ligament are contained: (1) the uterine tube
superiorly; (2) the round ligament of the uterus; (3) the ovary and its ligament; (4) the epoöphoron and paroöphoron; (5)
connective tissue; (6) unstriped muscular fibers; and (7) bloodvessels and nerves. The portion of the broad ligament which
stretches from the uterine tube to the level of the ovary is known by the name of the mesosalpinx. Between the fimbriated
extremity of the tube and the lower attachment of the broad ligament is a concave rounded margin, called the infundibulopelvic ligament.
The round ligaments (ligamentum teres uteri) are two flattened bands between 10 and 12 cm. in length, situated between
the layers of the broad ligament in front of and below the uterine tubes. Commencing on either side at the lateral angle of
the uterus, this ligament is directed forward, upward, and lateralward over the external iliac vessels. It then passes through
the abdominal inguinal ring and along the inguinal canal to the labium majus, in which it becomes lost. The round ligaments consists principally of muscular tissue, prolonged from the uterus; also of some fibrous and areolar tissue, besides
bloodvessels, lymphatics; and nerves, enclosed in a duplicature of peritoneum, which, in the fetus, is prolonged in the form
of a tubular process for a short distance into the inguinal canal. This process is called the canal of Nuck. It is generally
obliterated in the adult, but sometimes remains pervious even in advanced life. It is analogous to the saccus vaginalis,
which precedes the descent of the testis.
In addition to the ligaments just described, there is a band named the ligamentum transversalis colli (Mackenrodt) on either side of the cervix uteri. It is attached to the side of the cervix uteri and to the vault and lateral fornix of the vagina, and
is continuous externally with the fibrous tissue which surrounds the pelvic bloodvessels.
The form, size, and situation of the uterus vary at different periods of life and under different circumstances.
In the fetus the uterus is contained in the abdominal cavity, projecting beyond the superior aperture of the pelvis. The cervix is considerably larger than the body.
At puberty the uterus is pyriform in shape, and weighs from 14 to 17 gm. It has descended into the pelvis, the fundus being just below the level of the superior aperture of this cavity. The palmate folds are distinct, and extend to the upper part of
the cavity of the organ.
The position of the uterus in the adult is liable to considerable variation, depending chiefly on the condition of the bladder
and rectum. When the bladder is empty the entire uterus is directed forward, and is at the same time bent on itself at the
junction of the body and cervix, so that the body lies upon the bladder. As the latter fills, the uterus gradually becomes
more and more erect, until with a fully distended bladder the fundus may be directed backward toward the sacrum.
During menstruation the organ is enlarged, more vascular, and its surfaces rounder; the external orifice is rounded, its labia swollen, and the lining membrane of the body thickened, softer, and of a darker color.
During pregnancy the uterus becomes enormously enlarged, and in the eighth month reaches the epigastric region. The
increase in size is partly due to growth of preëxisting muscle, and partly to development of new fibers.
After parturition the uterus nearly regains its usual size, weighing about 42 gm.; but its cavity is larger than in the virgin
state, its vessels are tortuous, and its muscular layers are more defined; the external orifice is more marked, and its edges
present one or more fissures.
In old age the uterus becomes atrophied, and paler and denser in texture; a more distinct constriction separates the body
and cervix. The internal orifice is frequently, and the external orifice occasionally, obliterated, while the lips almost entirely
disappear.
The uterus is composed of three coats: an external or serous, a middle or muscular, and an internal or mucous.
The serous coat (tunica serosa) is derived from the peritoneum; it invests the fundus and the whole of the intestinal surface
of the uterus; but covers the vesical surface only as far as the junction of the body and cervix. In the lower fourth of the
intestinal surface the peritoneum, though covering the uterus, is not closely connected with it, being separated from it by a
layer of loose cellular tissue and some large veins.
The muscular coat (tunica muscularis) forms the chief bulk of the substance of the uterus. In the virgin it is dense, firm, of
a grayish color, and cuts almost like cartilage. It is thick opposite the middle of the body and fundus, and thin at the orifices
of the uterine tubes. It consists of bundles of unstriped muscular fibers, disposed in layers, intermixed with areolar tissue,
bloodvessels, lymphatic vessels, and nerves. The layers are three in number: external, middle, and internal. The external
and middle layers constitute the muscular coat proper, while the inner layer is a greatly hypertrophied muscularis mucosae.
During pregnancy the muscular tissue becomes more prominently developed, the fibers being greatly enlarged.
The external layer, placed beneath the peritoneum, is disposed as a thin plane on the vesical and intestinal surfaces. It consists of fibers which pass transversely across the fundus, and, converging at each lateral angle of the uterus, are continued
on to the uterine tube, the round ligament, and the ligament of the ovary: some passing at each side into the broad ligament,
and others running backward from the cervix into the sacrouterine ligaments. The middle layer of fibers presents no regularity in its arrangement, being disposed longitudinally, obliquely, and transversely. It contains more bloodvessels than either of the other two layers. The internal or deep layer consists of circular fibers arranged in the form of two hollow cones,
the apices of which surround the orifices of the uterine tubes, their bases intermingling with one another on the middle of
the body of the uterus. At the internal orifice these circular fibers form a distinct sphincter.
The mucous membrane (tunica mucosa) is smooth, and closely adherent to the subjacent tissue. It is continuous through
the fimbriated extremity of the uterine tubes, with the peritoneum; and, through the external uterine orifice, with the lining
of the vagina.
In the body of the uterus the mucous membrane is smooth, soft, of a pale red color, lined by columnar ciliated epithelium,
and presents, when viewed with a lens, the orifices of numerous tubular follicles, arranged perpendicularly to the surface.
The structure of the corium differs from that of ordinary mucous membranes, and consists of an embryonic nucleated and
highly cellular form of connective tissue in which run numerous large lymphatics. In it are the tube-like uterine glands,
lined by ciliated columnar epithelium. They are of small size in the unimpregnated uterus, but shortly after impregnation
become enlarged and elongated, presenting a contorted or waved appearance.
In the cervix the mucous membrane is sharply differentiated from that of the uterine cavity. It is thrown into numerous
oblique ridges, which diverge from an anterior and posterior longitudinal raphé. In the upper two-thirds of the canal, the
mucous membrane is provided with numerous deep glandular follicles, which secrete a clear viscid alkaline mucus; and, in
addition, extending through the whole length of the canal is a variable number of little cysts, presumably follicles which
have become occluded and distended with retained secretion. They are called the ovula Nabothi. The mucous membrane
covering the lower half of the cervical canal presents numerous papillae. The epithelium of the upper two-thirds is cylindrical and ciliated, but below this it loses its cilia, and gradually changes to stratified squamous epithelium close to the external orifice. On the vaginal surface of the cervix the epithelium is similar to that lining the vagina, viz., stratified squamous.
The vagina extends from the vestibule to the uterus, and is situated behind the bladder and in front of the rectum; it is directed upward and backward, its axis forming with that of the uterus an angle of over 90°, opening forward. Its walls are
ordinarily in contact, and the usual shape of its lower part on transverse section is that of an H, the transverse limb being
slightly curved forward or backward, while the lateral limbs are somewhat convex toward the median line; its middle part
has the appearance of a transverse slit. Its length is 6 to 7.5 cm. along its anterior wall, and 9 cm. along its posterior wall. It
is constricted at its commencement, dilated in the middle, and narrowed near its uterine extremity; it surrounds the vaginal
portion of the cervix uteri, a short distance from the external orifice of the uterus, its attachment extending higher up on the
posterior than on the anterior wall of the uterus. To the recess behind the cervix the term posterior fornix is applied, while
the smaller recesses in front and at the sides are called the anterior and lateral fornices.
Relations. - The anterior surface of the vagina is in relation with the fundus of the bladder, and with the urethra. Its posterior surface is separated from the rectum by the rectouterine excavation in its upper fourth, and by the rectovesical fascia in
its middle two-fourths; the lower fourth is separated from the anal canal by the perineal body. Its sides are enclosed between the Levatores ani muscles. As the terminal portions of the ureters pass forward and medialward to reach the fundus
of the bladder, they run close to the lateral fornices of the vagina, and as they enter the bladder are slightly in front of the
anterior fornix.
Structure. - The vagina consists of an internal mucous lining and a muscular coat separated by a layer of erectile tissue.
The mucous membrane (tunica mucosa) is continuous above with that lining the uterus. Its inner surface presents two longitudinal ridges, one on its anterior and one on its posterior wall. These ridges are called the columns of the vagina and
from them numerous transverse ridges or rugae extend outward on either side. These rugae are divided by furrows of variable depth, giving to the mucous membrane the appearance of being studded over with conical projections or papillae; they
are most numerous near the orifice of the vagina, especially before parturition. The epithelium covering the mucous membrane is of the stratified squamous variety. The submucous tissue is very loose, and contains numerous large veins which
by their anastomoses form a plexus, together with smooth muscular fibers derived from the muscular coat; it is regarded by
Gussenbauer as an erectile tissue. It contains a number of mucous crypts, but no true glands.
The muscular coat (tunica muscularis) consists of two layers: an external longitudinal, which is by far the stronger, and an
internal circular layer. The longitudinal fibers are continuous with the superficial muscular fibers of the uterus. The strongest fasciculi are those attached to the rectovesical fascia on either side. The two layers are not distinctly separable from
each other, but are connected by oblique decussating fasciculi, which pass from the one layer to the other. In addition to
this, the vagina at its lower end is surrounded by a band of striped muscular fibers, the Bulbocavernosus
External to the muscular coat is a layer of connective tissue, containing a large plexus of bloodvessels.
The erectile tissue consists of a layer of loose connective tissue, situated between the mucous membrane and the muscular
coat; imbedded in it is a plexus of large veins, and numerous bundles of unstriped muscular fibers, derived from the circular
muscular layer. The arrangement of the veins is similar to that found in other erectile tissues.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 20. Perineum: anatomy and relations.
The aim: to learn the anatomy and relations of perineum and its structures.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, proctologists, obstetritians etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 21. Endocrine glands: development, classifіcation, anatomy, functions.
The aim: to learn the anatomy and relations of endocrine glands.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, endocrinologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
There are certain organs which are very similar to secreting glands, but differ from them in one essential particular, viz.,
they do not possess any ducts by which their secretion is discharged. These organs are known as ductless glands. They are
capable of internal secretion - that is to say, of forming, from materials brought to them in the blood, substances which have
a certain influence upon the nutritive and other changes going on in the body. This secretion is carried into the blood
stream, either directly by the veins or indirectly through the medium of the lymphatics.
These glands include the thyroid, the parathyroids and the thymus; the pituitary body and the pineal body; the chromaphil
and cortical systems to which belong the suprarenals, the paraganglia and aortic glands, the glomus caroticum and perhaps
the glomus coccygeum. The spleen is usually included in this list and sometimes the lymph and hemolymph nodes described with the lymphatic system. Other glands as the liver, pancreas and sexual glands give off internal secretions, as do
the gastric and intestinal mucous membranes.
The Thyroid Gland (Glandula Thyreiodea; Thyroid Body) - The thyroid gland is a highly vascular organ, situated at the
front and sides of the neck; it consists of right and left lobes connected across the middle line by a narrow portion, the isthmus. Its weight is somewhat variable, but is usually about 30 grams. It is slightly heavier in the female, in whom it becomes
enlarged during menstruation and pregnancy.
The lobes (lobuli gl. thyreoideae) are conical in shape, the apex of each being directed upward and lateralward as far as
the junction of the middle with the lower third of the thyroid cartilage; the base looks downward, and is on a level with the
fifth or sixth tracheal ring. Each lobe is about 5 cm. long; its greatest width is about 3 cm., and its thickness about 2 cm.
The lateral or superficial surface is convex, and covered by the skin, the superficial and deep fasciae, the Sternocleidomastoideus, the superior belly of the Omohyoideus, the Sternohyoideus and Sternothyreoideus, and beneath the last muscle by
the pretracheal layer of the deep fascia, which forms a capsule for the gland. The deep or medial surface is moulded over
the underlying structures, viz., the thyroid and cricoid cartilages, the trachea, the Constrictor pharyngis inferior and posterior part of the Cricothyreoideus, the esophagus (particularly on the left side of the neck), the superior and inferior thyroid
arteries, and the recurrent nerves. The anterior border is thin, and inclines obliquely from above downward toward the middle line of the neck, while the posterior border is thick and overlaps the common carotid artery, and, as a rule, the parathyroids.
The isthmus (isthmus gl. thyreoidea) connects together the lower thirds of the lobes; it measures about 1.25 cm. in
breadth, and the same in depth, and usually covers the second and third rings of the trachea. Its situation and size present,
however, many variations. In the middle line of the neck it is covered by the skin and fascia, and close to the middle line,
on either side, by the Sternothyreoideus. Across its upper border runs an anastomotic branch uniting the two superior thyroid arteries; at its lower border are the inferior thyroid veins. Sometimes the isthmus is altogether wanting.
A third lobe, of conical shape, called the pyramidal lobe, frequently arises from the upper part of the isthmus, or from the
adjacent portion of either lobe, but most commonly the left, and ascends as far as the hyoid bone. It is occasionally quite
detached, or may be divided into two or more parts.
A fibrous or muscular band is sometimes found attached, above, to the body of the hyoid bone, and below to the isthmus
of the gland, or its pyramidal lobe. When muscular, it is termed the Levator glandulae thyreoideae.
Small detached portions of thyroid tissue are sometimes found in the vicinity of the lateral lobes or above the isthmus;
they are called accessory thyroid glands (glandulae thyreoideae accessoriae).
Development. - The thyroid gland is developed from a median diverticulum, which appears about the fourth week on the
summit of the tuberculum impar, but later is found in the furrow immediately behind the tuberculum. It grows downward
and backward as a tubular duct, which bifurcates and subsequently subdivides into a series of cellular cords, from which
the isthmus and lateral lobes of the thyroid gland are developed. The ultimo-branchial bodies from the fifth pharyngeal
pouches are enveloped by the lateral lobes of the thyroid gland; they undergo atrophy and do not form true thyroid tissue.
The connection of the diverticulum with the pharynx is termed the thyroglossal duct; its continuity is subsequently interrupted, and it undergoes degeneration, its upper end being represented by the foramen cecum of the tongue, and its lower
by the pyramidal lobe of the thyroid gland.
Structure. - The thyroid gland is invested by a thin capsule of connective tissue, which projects into its substance and imperfectly divides it into masses of irregular form and size. When the organ is cut into, it is of a brownish-red color, and is
seen to be made up of a number of closed vesicles, containing a yellow glairy fluid, and separated from each other by intermediate connective tissue.
This internal secretion of the thyroid is supposed to contain a specific hormone which acts as a chemical stimulus to other
tissues, increasing their metabolism.
The parathyroid glands are small brownish-red bodies, situated as a rule between the posterior borders of the lateral lobes
of the thyroid gland and its capsule. They differ from it in structure, being composed of masses of cells arranged in a more
or less columnar fashion with numerous intervening capillaries. They measure on an average about 6 mm. in length, and
from 3 to 4 mm. in breadth, and usually present the appearance of flattened oval disks. They are divided, according to their
situation, into superior and inferior. The superior, usually two in number, are the more constant in position, and are situated, one on either side, at the level of the lower border of the cricoid cartilage, behind the junction of the pharynx and
esophagus. The inferior, also usually two in number, may be applied to the lower edge of the lateral lobes, or placed at
some little distance below the thyroid gland, or found in relation to one of the inferior thyroid veins.
In man, they number four as a rule; fewer than four were found in less than 1 per cent. of over a thousand persons, but
more than four in over 33 per cent. of 122 bodies examined by Civalleri. In addition, numerous minute islands of parathyroid tissue may be found scattered in the connective tissue and fat of the neck around the parathyroid glands proper, and
quite distinct from them.
Development. - The parathyroid bodies are developed as outgrowths from the third and fourth branchial pouches. A pair of
diverticula arise from the fifth branchial pouch and form what are termed the ultimo-branchial bodies: these fuse with the
thyroid gland, but probably contribute no true thyroid tissue.
No doubt the parathyroid glands produce an internal secretion essential to the well-being of the human economy; but it is
still a matter of dispute what symptoms of disease are produced by their removal and suppression of their secretion. Pepere
believes that they show signs of exceptional activity during pregnancy, and that parathyroid insufficiency is a main factor
in the production of tetany in infants and adults, of eclampsia, and of certain sorts of fits. It is probable that the tetany following parathyroidectomy is due to the accumulation of ammonium carbonate and Kendall has suggested that the function
of the parathyroid is to convert ammonium carbonate into urea.
The thymus is a temporary organ, attaining its largest size at the time of puberty, when it ceases to grow, gradually dwindles, and almost disappears. If examined when its growth is most active, it will be found to consist of two lateral lobes
placed in close contact along the middle line, situated partly in the thorax, partly in the neck, and extending from the fourth
costal cartilage upward, as high as the lower border of the thyroid gland. It is covered by the sternum, and by the origins of
the Sternohyoidei and Sternothyreoidei. Below, it rests upon the pericardium, being separated from the aortic arch and great
vessels by a layer of fascia. In the neck it lies on the front and sides of the trachea, behind the Sternohyoidei and Sternothyreoidei. The two lobes generally differ in size; they are occasionally united, so as to form a single mass; and sometimes
separated by an intermediate lobe. The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces. It is about 5
cm. in length, 4 cm. in breadth below, and about 6 mm. in thickness. At birth it weighs about 15 grams, at puberty it weighs
about 35 grams; after this it gradually decreases to 25 grams at twentyfive years, less than 15 grams at sixty, and about 6
grams at seventy years.
Development. - The thymus appears in the form of two flask-shaped entodermal diverticula, which arise, one on either side,
from the third branchial pouch, and extend lateralward and backward into the surrounding mesoderm in front of the ventral
aortae. Here they meet and become joined to one another by connective tissue, but there is never any fusion of the thymus
tissue proper. The pharyngeal opening of each diverticulum is soon obliterated, but the neck of the flask persists for some
time as a cellular cord. By further proliferation of the cells lining the flask, buds of cells are formed, which become surrounded and isolated by the invading mesoderm. In the latter, numerous lymphoid cells make their appearance, and are
agregated to form lymphoid follicles. These lymphoid cells are probably derivatives of the entodermal cells which lined the
original diverticula and their subdivisions. Additional portions of thymus tissue are sometimes developed from the fourth
branchial pouches. Thymus continues to grow until the time of puberty and then begins to atrophy.
Each lateral lobe is composed of numerous lobules held together by delicate areolar tissue; the entire gland being enclosed
in an investing capsule of a similar but denser structure. The primary lobules vary in size from that of a pin’s head to that of
a small pea, and are made up of a number of small nodules or follicles, which are irregular in shape and are more or less
fused together, especially toward the interior of the gland. Each follicle is from 1 to 2 mm. in diameter and consists of a
medullary and a cortical portion, and these differ in many essential particulars from each other. The cortical portion is
mainly composed of lymphoid cells, supported by a network of finely branched cells, which is continuous with a similar
network in the medullary portion. This network forms an adventitia to the bloodvessels. In the medullary portion the reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number, and there are found peculiar nest-like
bodies, the concentric corpuscles of Hassall. These concentric corpuscles are composed of a central mass, consisting of one
or more granular cells, and of a capsule which is formed of epithelioid cells. They are the remains of the epithelial tubes
which grow out from the third branchial pouches of the embryo to form the thymus.
Each follicle is surrounded by a vascular plexus, from which vessels pass into the interior, and radiate from the periphery
toward the center, forming a second zone just within the margin of the medullary portion. In the center of the medullary
portion there are very few vessels, and they are of minute size.
The function of the thymus is obscure. It seems to furnish during the period of growth an internal secretion concerned with
some phases of body metabolism, especially that of the sexual glands.
The hypophysis consists of an anterior and a posterior lobe, which differ from one another in their mode of development
and in their structure. The anterior lobe is the larger and is somewhat kidney-shaped, the concavity being directed backward
and embracing the posterior lobe. It consists of a pars anterior and a pars intermedia, separated from each other by a narrow
cleft, the remnant of the pouch or diverticulum. The pars anterior is extremely vascular and consists of epithelial cells of
varying size and shape, arranged in cord-like trabeculae or alveoli and separated by large, thin-walled bloodvessels. The
pars intermedia is a thin lamina closely applied to the body and neck of the posterior lobe and extending onto the neighboring parts of the brain; it contains few bloodvessels and consists of finely granular cells between which are small masses of
colloid material. The pars intermedia in spite of the fact that it arises in common with the pars anterior from the ectoderm
of the primitive buccal cavity is often considered as a part of the posterior lobe which arises from the floor of the third ventricle of the brain. Although of nervous origin the posterior lobe contains no nerve cells or fibers. It consists of neuroglia
cells and fibers and is invaded by columns which grow into it from the pars intermedia; imbedded in it are large quantities
of a colloid substance histologically similar to that found in the thyroid gland. In certain of the lower vertebrates, e.g., fishes, nervous structures are present, and the lobe is of large size.
From the pars intermedia a substance, no doubt an internal secretion, causes constriction of the bloodvessels with rise of
arterial blood-pressure. This substance seems to have a stimulating effect on most of the smooth muscles, acting directly
upon the muscle causing contraction. It also increases the secretion of the urine; of the mammary glands when in functional
activity; and of the cerebrospinal fluid. Extracts of this lobe also influence the general metabolism of the carbohydrates by
accelerating the process of glycogenolysis in the liver.
The pars anterior exercises a stimulating effect on the growth of the skeleton and probably on connective tissues in general.
Enlargement of the hypophysis and of the cavity of the sella turcica are found in the rare disease acromegaly, which is
characterized by gradual enlargement of the face, hands, and feet, with headache and often a peculiar type of blindness.
This blindness is due to the pressure of the enlarging hypophysis on the optic chiasma.
Development of the Hypophysis Cerebri. - This in the adult consists of a large anterior, consisting of the pars anterior and
the pars intermedia, and a small posterior lobe: the former is derived from the ectoderm of the stomodeum, the latter from
the floor of the fore-brain. About the fourth week there appears a pouchlike diverticulum of the ectodermal lining of the
roof of the stomodeum. This diverticulum, pouch of Rathke, is the rudiment of the anterior lobe of the hypophysis; it extends upward in front of the cephalic end of the notochord and the remnant of the buccopharyngeal membrane, and comes
into contact with the under surface of the fore-brain. It is then constricted off to form a closed vesicle, but remains for a
time connected to the ectoderm of the stomodeum by a solid cord of cells. Masses of epithelial cells form on either side and
in the front wall of the vesicle, and by the growth between these of a stroma from the mesoderm the development of the
anterior lobe is completed. The upwardly directed hypophyseal involution becomes applied to the antero-lateral aspect of a
downwardly directed diverticulum from the base of the fore-brain. This diverticulum constitutes the future infundibulum in
the floor of the third ventricle while its inferior extremity becomes modified to form the posterior lobe of the hypophysis.
In some of the lower animals the posterior lobe contains nerve cells and nerve fibers, but in man and the higher vertebrates
these are replaced by connective tissue. A canal, craniopharyngeal canal, is sometimes found extending from the anterior
part of the fossa hypophyseos of the sphenoid bone to the under surface of the skull, and marks the original position of
Rathke’s pouch; while at the junction of the septum of the nose with the palate traces of the stomodeal end are occasionally
present.
The pineal body (epiphysis) is a small reddish-gray body, about 8 mm. in length which lies in the depression between the
superior colliculi. It is attached to the roof of the third ventricle near its junction with the mid-brain. It develops as an outgrowth from the third ventricle of the brain.
In early life it has a glandular structure which reaches its greatest development at about the seventh year. Later, especially
after puberty, the glandular tissue gradually disappears and is replaced by connective tissue.
Structure. - The pineal body is destitute of nervous substance, and consists of follicles lined by epithelium and enveloped
by connective tissue. These follicles contain a variable quantity of gritty material, composed of phosphate and carbonate of
calcium, phosphate of magnesium and ammonia, and a little animal matter.
It contains a substance which if injected intravenously causes fall of blood-pressure. It seems probable that the gland furnishes an internal secretion in children that inhibits the development of the reproductive glands since the invasion of the
gland in children, by pathological growths which practically destroy the glandular tissue, results in accelerated development of the sexual organs, increased growth of the skeleton and precocious mentality.
Chromaphil or chromaffin cells, so-called because they stain yellow or brownish with chromium salts, are associated with
the ganglia of the sympathetic nervous system.
Development. - They arise in common with the sympathetic cells from the neural crest, and are therefore ectodermal in
origin. The chromaphil and sympathetic cells are indistinguishable from one another at the time of their migration from the
spinal ganglia to the regions occupied in the adult. Differentiation of chromaphil cells begins in embryos about 18 mm. in
length but is not complete until about birth. The chromaphiloblasts increase in size more than the sympathoblasts and stain
less intensely with ordinary dyes. Later the chrome reaction develops. The aortic bodies differentiate first and are prominent in 20 mm. embryos. The paraganglia of the sympathetic plexuses differentiate next and last of all the paraganglia of
the sympathetic trunk. The carotid body is completely differentiated in 30 mm. embryos. After birth the chromaphil organs
degenerate but the paraganglia can be recognized with the microscope in sites originally occupied by them.
The paraganglia are small groups of chromaphil cells connected with the ganglia of the sympathetic trunk and the ganglia
of the celiac, renal, suprarenal, aortic and hypogastric plexuses. They are sometimes found in connection with the ganglia
of other sympathetic plexuses. None have been found with the sympathetic ganglia associated with the branches of the trigeminal nerve.
The aortic glands or bodies are the largest of these groups of chromaphil cells and measure in the newborn about 1 cm. in
length. They lie one on either side of the aorta in the region of the inferior mesenteric artery. They decrease in size with age
and after puberty are only visible with the microscope. About forty they disappear entirely. Other groups of chromaphil
cells have been found associated with the sympathetic plexuses of the abdomen independently of the ganglia.
The medullary portions of the suprarenal glands and the glomus caroticum belong to the chromaphil system.
The Suprarenal Glands (Glandulae Suprarenalis; Adrenal Capsule) - The suprarenal glands are two small flattened bodies
of a yellowish color, situated at the back part of the abdomen, behind the peritoneum, and immediately above and in front
of the upper end of each kidney; hence their name. The right one is somewhat triangular in shape, bearing a resemblance to
a cocked hat; the left is more semilunar, usually larger, and placed at a higher level than the right. They vary in size in different individuals, being sometimes so small as to be scarcely detected: their usual size is from 3 to 5 cm. in length, rather
less in width, and from 4 to 6 mm. in thickness. Their average weight is from 1.5 to 2.5 gm. each.
Development. - Each suprarenal gland consists of a cortical portion derived from the celomic epithelium and a medullary
portion originally composed of sympatho-chromaffin tissue. The cortical portion is first recognizable about the beginning
of the fourth week as a series of buds from the celomic cells at the root of the mesentery. Later it becomes completely separated from the celomic epithelium and forms a suprarenal ridge projecting into the celom between the mesonephros and the
root of the mesentery. Into this cortical portion cells from the neighboring masses of sympatho-chromaffin tissue migrate
along the line of its central vein to reach and form the medullary portion of the gland.
Relations. - The relations of the suprarenal glands differ on the two sides of the body.
The right suprarenal is situated behind the inferior vena cava and right lobe of the liver, and in front of the diaphragm and
upper end of the right kidney. It is roughly triangular in shape; its base, directed downward, is in contact with the medial
and anterior aspects of the upper end of the right kidney. It presents two surfaces for examination, an anterior and a posterior. The anterior surface looks forward and lateralward, and has two areas: a medial, narrow, and non-peritoneal, which lies
behind the inferior vena cava; and a lateral, somewhat triangular, in contact with the liver. The upper part of the latter surface is devoid of peritoneum, and is in relation with the bare area of the liver near its lower and medial angle, while its inferior portion is covered by peritoneum, reflected onto it from the inferior layer of the coronary ligament; occasionally the
duodenum overlaps the inferior portion. A little below the apex, and near the anterior border of the gland, is a short furrow
termed the hilum, from which the suprarenal vein emerges to join the inferior vena cava. The posterior surface is divided
into upper and lower parts by a curved ridge: the upper, slightly convex, rests upon the diaphragm; the lower, concave, is in
contact with the upper end and the adjacent part of the anterior surface of the kidney.
The left suprarenal, slightly larger than the right, is crescentic in shape, its concavity being adapted to the medial border of
the upper part of the left kidney. It presents a medial border, which is convex, and a lateral, which is concave; its upper end
is narrow, and its lower rounded. Its anterior surface has two areas: an upper one, covered by the peritoneum of the omental
bursa, which separates it from the cardiac end of the stomach, and sometimes from the superior extremity of the spleen; and
a lower one, which is in contact with the pancreas and lienal artery, and is therefore not covered by the peritoneum. On the
anterior surface, near its lower end, is a furrow or hilum, directed downward and forward, from which the suprarenal vein
emerges. Its posterior surface presents a vertical ridge, which divides it into two areas; the lateral area rests on the kidney,
the medial and smaller on the left crus of the diaphragm.
The surface of the suprarenal gland is surrounded by areolar tissue containing much fat, and closely invested by a thin
fibrous capsule, which is difficult to remove on account of the numerous fibrous processes and vessels entering the organ
through the furrows on its anterior surface and base.
Small accessory suprarenals (glandulae suprarenales accessoriae) are often to be found in the connective tissue around the
suprarenals. The smaller of these, on section, show a uniform surface, but in some of the larger a distinct medulla can be
made out.
On section, the suprarenal gland is seen to consist of two portions: an external or cortical and an internal or medullary. The
former constitutes the chief part of the organ, and is of a deep yellow color; the medullary substance is soft, pulpy, and of a
dark red or brown color.
Glomus Caroticum (Carotid Glands; Carotid Bodies) - The carotid bodies, two in number, are situated one on either side of
the neck, behind the common carotid artery at its point of bifurcation into the external and internal carotid trunks. They are
reddish brown in color and oval in shape, the long diameter measuring about 5 mm.
Each is invested by a fibrous capsule and consists largely of spherical or irregular masses of cells, the masses being more
or less isolated from one another by septa which extend inward from the deep surface of the capsule. The cells are polyhedral in shape, and each contains a large nucleus imbedded in finely granular protoplasm, which is stained yellow by chromic salts. Numerous nerve fibers, derived from the sympathetic plexus on the carotid artery, are distributed throughout the
organ, and a net-work of large sinusoidal capillaries ramifies among the cells.
Glomus Coccygeum (Coccygeal Gland or Body; Luschka’s Gland) - The glomus coccygeum is placed in front of, or immediately below, the tip of the coccyx. It is about 2.5 mm. in diameter and is irregularly oval in shape; several smaller nodules are found around or near the main mass.
It consists of irregular masses of round or polyhedral cells, the cells of each mass being grouped around a dilated sinusoidal capillary vessel. Each cell contains a large round or oval nucleus, the protoplasm surrounding which is clear, and is not
stained by chromic salts.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 6. Review of urinary system. Development of urinary system.
The aim: to learn the general structure and relations of urinary system, development of its components.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, nephrologists, obstetritians etc.
The development of the urinary system is closely related to that of the genital system which will be described, though, in a
separate module. The urinary organs consist of the kidneys (which produce urine, among other things), the ureter (transport
of the urine from the kidneys to the bladder), the bladder (temporary storage for the urine) and the urethra (transport of the
urine from the bladder to the external world).
In all vertebrates the kidneys and ureters develop out of the intermediate mesoderm, whereas bladder and urethra derive
from the urogenital sinus. Due to the lateral folding, the intermediate mesoderm is shifted ventrally and loses its connection with the somites and the lateral mesoderm.
The nephrogenic cord develops out of the intermediate mesoderm 9 and extends from the cervical to the caudal region. It
becomes segmented like the paraxial mesoderm (somites). This segmentation is easily seen in the cranial region, and is
rudimentary in the middle region. In the caudal region it is no longer present, as we will describe in detail below. Due to the
growth of the inner structures of the embryo, the tissue lying most laterally is displaced ventrally. This leads not only to a
separation of the nephrogenic cord from the paraxial and lateral mesoderm, but also to a coalescence of certain median
structures such as the two dorsal aortas 12which fuse to form the definitive (median) aorta.
The kidneys develop along a cranio-caudal gradient. Typically, the development passes through three stages:
Pronephros
Mesonephros
Metanephros
In principle, for all three developmental stages with similar designations, the same embryonic anlage - the intermediate
mesoderm - is involved.
The term "holonephros" can thus be employed to designate all the parts of the urinary system that arise from it. The first
two developmental stages have a transitory character and the definitive kidneys actually develop from the metanephros
stage.
The pronephros develops during the 4th week, beginning in the cranial part of the nephrogenic cord and it atrophies during
the 5th week. Three characteristic pronephros structures can be distinguished: The pronephros duct in the neck region. The
pronephros tubules. The external or coelom glomeruli that have been shown to exist in humans.
Beginning with the 4th week, conforming to the cranio-caudal gradient, the pronephros in the neck region divides into independent masses of cells, the nephrotomes 11.
Each nephrotome develops into an epithelialized pronephros glomerulus. Laterally, they form the pronephros tubules that
can partly bind with the coelom. Via the fusion of these tubules between two nephrotomes the hollow pronephros duct arises that is the anlage of the pronephric collecting duct. In humans, this pronephros system corresponds more to a primitive
and transient structure that is functionally of no importance. According to the classical view, the pronephros duct stops in
the caudal region at the level of the 13th -14th somite and then goes over into the mesonephric duct (Wolffian duct).
The mesonephros differentiates itself during the 4th week and after the 8th week it degenerates. It replaces the pronephros
and develops from three structures: Nephrogenic cord in the dorso-lumbal region. Mesonephric duct. Glomerular capillary
network.
The mesonephric duct forms on the dorsal side of the nephrogenic cord at the level of the 9th somite. Initially it consists of
a solid mesenchymal cord of cells 11. It releases itself from the nephrogenic cord and is finally localized under the ectoderm, which probably plays an inductive role in its formation.
Released from the nephrogenic cord, it develops in the caudal direction and canalizes itself at the same time 12, in order to
finally end in the cloaca. As soon as it is canalized one calls it the mesonephric duct (Wolffian duct). At the site where the
mesonephric duct (Wolffian duct) discharges into the cloaca, the rear wall of the bladder forms.
Mesonephros: first excretory organ
Shortly after the differentiation of the mesonephric duct, through mesenchymal-epithelial transformation, the mesonephric
vesicles 11 arise out of the nephrogenic cord, which represents a mesoderm condensate. Via the mesonephric tubules they
connect up with the mesonephric duct 14. This differentiation takes place bilaterally in the area between the upper thoracic
region (Th1) and the lumbar region (L3). A cranio-caudal gradient is also visible here. To the extent in which new mesonephric vesicles and tubules develop caudally, the cranial elements begin to atrophy so that never more than 30 pairs exist
in the mesonephros. They form the excretory system that closely resembles the adult nephrons.
Medially, the mesonephric vesicle dead-ends in that it forms a funnel (Bowman's capsule). Each of these funnels surrounds
a tuft of capillaries (glomerulus), which have also arisen in the nephrogenic tissue and come from lateral (visceral) branches of the dorsal aorta. They drain into the inferior cardinal vein.
The capsule with glomerulus together form a renal corpuscle. A renal corpuscle and its associated tubule are called a nephron and the functional unit an excretory mesonephric unit.
The production of urine begins in the mesonephros during the 6th week 17. After the 10th week these nephrons become
inactive and atrophy. While in the female all mesonephric tubules atrophy completely, in the male a few that lie caudally
remain in order to develop into the testicular efferent ducts.
The metanephros develops from three intermediate mesoderm structures of the sacral region: Ureter anlage. Metanephric
vesicle. Glomerular capillary network
The ureter anlage is an epithelial diverticulum from the caudal part of the mesonephric duct (Wolffian duct) in the area of
the first sacral vertebra (S1).
The anlage intrudes into the metanephric vesicle and forms the extra- and intrarenal excretory passages.
The metanephric blastema corresponds to the sacral part of the nephrogenic cord below L3. It is mesenchymal tissue out of
which the metanephric vesicles arise. From these originate the nephrons (= functional units of the kidneys).
At present it is still not clear whether the glomerular capillary network develops through vasculogenesis (direct development of vessels from the metanephric vesicles) or through angiogenesis (development from existing vessels of the metanephros).
The interaction between the ureter anlage (epithelial tissue) and the metanephric blastema (mesenchyma) is of decisive importance for renal development. The development of the kidneys represents a classical model of a sequential and reciprocal
induction between epithelium and mesenchyma. For this reason it is frequently used for investigating the molecular cell
mechanisms that play a role in the entire organogenesis.
Renal development comprises a whole series of developmental processes such as forming an epithelial tree structure, interactive tissue induction, differentiation, polarization, migration, cell adhesion and finally the epithelio-mesenchymal transformation.
During the genesis of the metanephros the metanephric blastema first induces the branching of the ureter anlage, which, for
its part, then lets the metanephric vesicle form into a predetermined blastema. Through the transformation into epithelial
tissue, the renal tubules form and finally the nephrons emerge. The most recent molecular-biologic research, mainly on
transgenic mice, has shown that several factors are involved in this process. These various factors can be gone into only
briefly in this chapter; those wishing to dig deeper can have a look at the cited references.
The ureter anlage is an epithelial diverticulum which arises from the caudal portion of the mesonephric duct (Wolffian
duct) at the level of the first sacral vertebra. Its enlarged end grows in the dorso-cranial direction and projects into the metanephric blastema. It is the origin of the intra- and extrarenal excretory passages: Ureter. Renal pelvis. Major and minor
calices. Collecting ducts
The cranial end of the ureter anlage subdivides dichotomically many times due to the inductive effect of the metanephric
blastema.
The renal pelvis arises from the swollen end of the ureteric bud that subdivides 4 times over the course of the 4th to 6th
weeks. 16 branches arise from this that partially then coalesce again in order to finally form 2 to 4 major calices.
At around the 7th week the minor calices start to develop. They discharge into the major calices. Further dichotomic
branching follow - up to the 15th generation (roughly 32 weeks). Thereby the caliber of the tubules is reduced more and
more so that finally 1-3 millions collecting ducts are formed in the periphery of the metanephric blastema
The process of nephron formation is complicated and thus subdivided into various steps:
The metanephric blastema surrounds each newly formed collecting duct. It condenses in order to form peritubular cell aggregates.
Through induction signals, derived from the ureter anlage, the mesenchymal cells transform themselves and form vesicles.
These vesicles grow longer and form an "S"-shaped tubule with three sections.
The epithelial vesicle secretes angiogenic factors. Thereby, over the course of the further development, endothelial cells are
brought into the glomerular capsule. As soon as the afferent vessels come into close contact with the vesicular epithelium,
it flattens and forms a cup with a bilaminar structure, Bowman's.
At the same time as the formation of the renal corpuscle, the distal end of the epithelial vesicle fuses with the neighboring
collecting duct. The metanephros thus becomes able to function and can filter the plasma from the glomeruli. Through the
proximal tubule the glomerular filtrate (primary urine) gets into the intermediate tubule, the distal tubule, connecting tubules and collecting duct. In these tubules the secondary urine arises through resorption and secretion processes. It then
reaches the renal pelvis and, via the ureter, the bladder. During the pregnancy, the fetal urine is excreted into the amniotic
cavity.
At birth the kidneys have a multilobular appearance, due to the development of the ureter anlage in the metanephric blastema. Normally, towards the end of the fetal period, the lobes are considerably smoothed, but they still exist until after
birth.
Completion of the smoothing follows during childhood by the increase in volume of the connective tissue and the increase
in size of the nephrons without any change in their number. With only few exceptions, adult kidneys no longer exhibit any
lobulation.
Since the renal architecture is finalized between the 5th and 15th weeks of intrauterine development; organogenesis of the
kidneys lasts well beyond the embryonic phase until far into the fetal period.
The metanephros is formed in the sacral region at the level of the first sacral vertebra (S1) and the bifurcation of the aorta.
In the adult, the kidney lies at the upper lumbar level. The "migration" (ascent) of the kidney occurs between the 6th and
9th week and the kidneys finally come to lie at the level of the 12th thoracal vertebra (Th12) under the suprarenal glands.
The mechanism that leads to this ascent of the kidneys is not an active migration but rather much more the result of the
differing growths of the sacral and lumbar regions, which lead to an unfolding of the lower pole of the embryonic body.
During its ascent, the kidney is supplied by a number of transitory vessels that all originate from the aorta. The definitive
renal arteries stem from the lumbar region of the aorta, while the transitory vessels normally disappear.
It must also be mentioned here that during their development the kidneys turn 90° towards the vertebral cords, so that the
hili are medially oriented at the end, while they originally face ventrally.
We have seen that the upper urinary system - consisting of the collecting ducts, the calices, the renal pelvis, and the ureters
- arises from the ureter anlage.
The lower urinary system - composed of the bladder and the urethra - is formed from the endoderm of the posterior intestine.
Separating the cloaca
In stage 13 13 the cloaca is the common end of the rectal tube and the urogenital tract. Towards the outside it is closed by
the cloacal membrane.
Between the 4th and 6th weeks the urorectal septum separates the cloaca into a primary urogenital sinus (ventrally) and the
rectum (dorsally).
The bladder and the pelvic limb of the urethra arise from the primary urogenital sinus and the caudal portion of the urethra
comes from the definitive urogenital sinus.
The urorectal septum divides the cloacal membrane into two membranes: the urogenital membrane (ventrally) and the anal
membrane (dorsally).
These two membranes atrophy 19, like the bucco-pharyngeal membrane 11, in order to form the intestinal and urogenital
openings.
The bladder develops from the upper part of the urogenital sinus (UGS) and is connected with the allantois.
The allantois is obliterated during the development and forms a fibrous cord, the urachus, which following birth becomes
the median umbilical ligament.
While the cloaca is being divided, the caudal, originally common part of the mesonephric duct (Wolffian duct) and the ureter anlage is taken up into the upper, postero-lateral wall of the urogenital sinus (future bladder).
The rapid growth of the back wall of the urogenital sinus has the result that the common lowest part of the ureter and the
mesonephric duct (Wolffian duct) are both taken up into the bladder wall. Further complicated growth processes have the
result that the ureteral orifices and the orifice locations of the mesonephric duct (Wolffian duct) go through a cranio-caudal
position exchange during the course of the further development. The ureteral openings appear to migrate thereby in a cranio-lateral direction and the mesonephros orifices appear to be shifted caudo-medially. The triangular zone that is thus created is termed the vesical trigonum. In males, the wolffian duct forms the future deferent duct on both sides.
The trigonum thus originates from the mesoderm while the ventral bladder wall has an endodermal origin. Later, though,
the trigonum will be completely covered by endodermal epithelial cells. The smooth musculature of the bladder develops
during the 12th week from the splanchnopleural mesoderm, which coats the endoderm on the outside.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 7. Sex differences of pelvic organs.
The aim: to learn the anatomy and relations of pelvic organs in male and female.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, gynaecologists, urologists etc.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 8. Structure, function and relations of female external genital organs. Development of genital organs.
The aim: to learn the anatomy and relations of ureters, urinary bladder and urethra.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, gynaecologists, urologists etc.
The external genital organs of the female are: the mons pubis, the labia majora et minora pudendi, the clitoris, the vestibule
of the vagina, the bulb of the vestibule, and the greater vestibular glands. The term pudendum or vulva, as generally applied, includes all these parts.
The Mons Pubis (commissura labiorum anterior; mons Veneris), the rounded eminence in front of the pubic symphysis, is
formed by a collection of fatty tissue beneath the integument. It becomes covered with hair at the time of puberty.
The Labia Majora (labia majora pudendi) are two prominent longitudinal cutaneous folds which extend downward and
backward from the mons pubis and form the lateral boundaries of a fissure or cleft, the pudendal cleft or rima, into which
the vagina and urethra open. Each labium has two surfaces, an outer, pigmented and covered with strong, crisp hairs; and
an inner, smooth and beset with large sebaceous follicles. Between the two there is a considerable quantity of areolar tissue,
fat, and a tissue resembling the dartos tunic of the scrotum, besides vessels, nerves, and glands. The labia are thicker in
front, where they form by their meeting the anterior labial commissure. Posteriorly they are not really joined, but appear to
become lost in the neighboring integument, ending close to, and nearly parallel with, each other. Together with the connecting skin between them, they form the posterior labial commissure or posterior boundary of the pudendum. The interval
between the posterior commissure and the anus, from 2.5 to 3 cm. in length, constitutes the perineum. The labia majora
correspond to the scrotum in the male.
The Labia Minora (labia minora pudendi; nymphae) are two small cutaneous folds, situated between the labia majora, and
extending from the clitoris obliquely downward, lateralward, and backward for about 4 cm. on either side of the orifice of
the vagina, between which and the labia majora they end; in the virgin the posterior ends of the labia minora are usually
joined across the middle line by a fold of skin, named the frenulum of the labia or fourchette. Anteriorly, each labium mi-
nus divides into two portions: the upper division passes above the clitoris to meet its fellow of the opposite side, forming a
fold which overhangs the glans clitoridis, and is named the preputium clitoridis; the lower division passes beneath the clitoris and becomes united to its under surface, forming, with its fellow of the opposite side, the frenulum of the clitoris. On the
opposed surfaces of the labia minora are numerous sebaceous follicles.
The Clitoris is an erectile structure, homologous with the penis. It is situated beneath the anterior labial commissure, partially hidden between the anterior ends of the labia minora. It consists of two corpora cavernosa, composed of erectile tissue enclosed in a dense layer of fibrous membrane, united together along their medial surfaces by an incomplete fibrous
pectiniform septum; each corpus is connected to the rami of the pubis and ischium by a crus; the free extremity (glans clitoridis) is a small rounded tubercle, consisting of spongy erectile tissue, and highly sensitive. The clitoris is provided like
the penis, with a suspensory ligament, and with two small muscles, the Ischiocavernosi, which are inserted into the crura of
the clitoris.
The Vestibule (vestibulum vaginae). - The cleft between the labia minora and behind the glans clitoridis is named the vestibule of the vagina: in it are seen the urethral and vaginal orifices and the openings of the ducts of the greater vestibular
glands.
The external urethral orifice (orificium urethrae externum; urinary meatus) is placed about 2.5 cm. behind the glans clitoridis and immediately in front of that of the vagina; it usually assumes the form of a short, sagittal cleft with slightly raised
margins.
The vaginal orifice is a median slit below and behind the opening of the urethra; its size varies inversely with that of the
hymen.
The hymen is a thin fold of mucous membrane situated at the orifice of the vagina; the inner edges of the fold are normally in contact with each other, and the vaginal orifice appears as a cleft between them. The hymen varies much in shape.
When stretched, its commonest form is that of a ring, generally broadest posteriorly; sometimes it is represented by a semilunar fold, with its concave margin turned toward the pubes. Occasionally it is cribriform, or its free margin forms a membranous fringe. It may be entirely absent, or may form a complete septum across the lower end of the vagina; the latter condition is known as an imperforate hymen. It may persist after copulation, so that its presence cannot be considered a sign of
virginity. When the hymen has been ruptured, small rounded elevations known as the carunculae hymenales are found as its
remains. Between the hymen and the frenulum of the labia is a shallow depression, named the navicular fossa.
The Bulb of the Vestibule (bulbus vestibuli; vaginal bulb) is the homologue of the bulb and adjoining part of the corpus
cavernosum urethrae of the male, and consists of two elongated masses of erectile tissue, placed one on either side of the
vaginal orifice and united to each other in front by a narrow median band termed the pars intermedia. Each lateral mass
measures a little over 2.5 cm. in length. Their posterior ends are expanded and are in contact with the greater vestibular
glands; their anterior ends are tapered and joined to one another by the pars intermedia; their deep surfaces are in contact
with the inferior fascia of the urogenital diaphragm; superficially they are covered by the Bulbocavernosus.
The Greater Vestibular Glands (glandulae vestibularis major [Bartholini]; Bartholin’s glands) are the homologues of the
bulbo-urethral glands in the male. They consist of two small, roundish bodies of a reddish-yellow color, situated one on
either side of the vaginal orifice in contact with the posterior end of each lateral mass of the bulb of the vestibule. Each
gland opens by means of a duct, about 2 cm. long, immediately lateral to the hymen, in the groove between it and the labium minus.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 9. Development, anatomy, function and relations of gonads.
The aim: to learn the anatomy and relations of male and female genital glands.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, nephrologists etc.
The development of the genital apparatus accompanies that of the urinary system (formation of the urinary apparatus). It
also has its origin in the intermediate mesoderm and urogenital sinus. The primordial germ cells share in the formation of
the gonads, but have an ectodermal origin 3. In males, the development of the testes is closely tied with that of the mesonephros. In females, on the other hand, the mesonephros plays no role at all.
The intermediate mesoblast is the origin of an elongated structure, the urogenital ridge (crista urogenitalis), which lies on
both sides of the midline between the lateral mesoderm and the root of the dorsal mesenterium of the embryo. It consists of
two main components, the nephrogenic cord, out of which the urinary apparatus arises and the genital ridge as the origin of
the gonads. The genital ridge extends from the upper thorax region to the level of the cloaca. The true gonad anlage develops, though, out of only the middle area. The cranial and caudal parts of the urogenital ridge form the upper and lower gonadal bands, respectively, that as embryonic structures secure the gonads cranially and caudally.
The gonads arise from two very different kinds of cells that originate in the embryo:·
The primordial germ cells (PGC) will form the gametes (sperm cells and oocytes). These cells come from the ectoderm, but
they separate themselves from it at a very early stage in the development.
The somatic cells with nourishing functions surround the primordial germ cells and form the somatic gonadal blastema. In
the testes the supporting cells (Sertoli) and the interstitial cells (Leydig) are involved, in the ovary the follicle cells and the
theca cells.
Their origin is still a matter of discussion, however, whereby three possible sources come into question: mesonephros, local mesenchyma, as well as superficial epithelial cells (coelomic epithelium).
The primordial germ cells (PGC) already appear at the time of gastrulation in the epiblast and complete an emigration out
of the embryo into the wall of the yolk sac (umbilical vesicle). Thanks to the collaboration of three factors - the folding of
the embryo, chemotactic factors and ameboid movements - they get from here into the wall of the intestinal tract within the
embryo again and, via the dorsal mesentery, into the gonadal ridge. During their migration, which takes place between the
4th and 6th weeks 11-14, they multiply through mitosis.
Like the nephrogenic cord the gonadal ridge extends from the heart region to the location near the cloaca. In the time between the 4th and 6th week 11-14 the middle section of this gonadal ridge develops into a gonad anlage in that cells of the
coelomic epithelium proliferate there. The immigrated PGC penetrate into this thickened zone of the coelomic epithelium.
The indifferent gonads thus assemble themselves from cells of various origins, whereby, as a result, the primordial germ
cells and the local somatic blastema influence each other reciprocally.
The local coelomic mesenchyma underneath also multiplies. The coelomic epithelium, which now becomes multi-layered,
loses for now its basal membrane. Gonadal cords arise that surround the PGC and extend into the depths. One knows that in the male - mesonephric cells are also involved, but it is unknown whether in females the cells immigrate as far as the
gonadal ridge.
Up to the 6th week male and female gonads cannot be distinguished. The gonadal cords and the PGC can be found both in
the cortical as well as in the medullar zones of the future gonads.
The testes differentiate themselves earlier than the ovaries, namely in the course of the 7th week 18 (44 days).
Responsible for this is the SRY gene on the Y chromosome that induces the development of the testes through the activation of a series of further genes (sex-determining genetic factors and hormones).
Development of the testis parenchyma
The differentiation of Sertoli's supporting cells form the first step in the organogenesis of the testes. These cells come - in
any case in mice - from pluripotent coelomic epithelial cells of the gonadal ridge. In the gonadal anlage, through the influence of genetic products that are activated by the SRY, they form intercellular membrane connections and in this way surround more and more the primordial germ cells, while growing at the same time as gonadal cords into the medulla. In addition, in a male embryo, cells of mesonephric origin are involved as well in forming the gonadal cords, by accumulating on
the outside of the gonadal cords and forming the peritubular myoblasts. From the gonadal cords the testicular cords form
that then differentiate to become the convoluted seminiferous tubules (500 to 1000) and straight seminiferous tubules of the
mature testicles.
Until puberty the coiled testicular cords are filled. During puberty they form lumens and are from then on called convoluted
seminiferous tubules. The germ cells on the other hand divide mitotically, but their meiosis begins only with puberty. The
deep portions of the coiled testicular cords, which are delimited by septa, are stretched and are called straight seminiferous
tubules. These last go over into the rete testis, which is a labyrinth of small passages in the tunica albuginea. The thin wall
possesses a cubic epithelium. During the 9th week, from 5-12 mesonephric tubules the efferent ductules form that bind with
the rete testis in the 3rd month.
The deep medullary portion of the testicular cords are stretched and converge towards the rete testis, which on the other
side goes over into the efferent ductules (mesonephric tubules) that go out from the mesonephric duct (Wolff). From the 8th
week the latter form compact convolutions, the ductus epididymidis. Outside the epididymis this continues as the deferent
duct. The tunica albuginea is now a taut connective tissue layer that envelops the testicles. Connective tissue septa subdivide the testicles into lobules.
The efferent ductules form the connection between the rete testis and mesonephric duct. Towards the end of the 8th week,
under the influence of testosterone, the cranial part of the mesonephric duct gets to be tightly coiled and so forms the ductus
epididymidis which, outside the epididymis, continues as the deferent duct. (see: the inner sex passages)
After the 8th week certain mesenchymal cells between the testicular cords differentiate to become interstitial cells (Leydig),
which produce testosterone. The testes thus represent an endocrine gland that produces androgens. The origin of these cells
is still unclear – one suspects that a steroid-producing population of cells in the ventral part of the mesonephros differentiate and form both the origin of the adrenal cortex cells and also interstitial cells (Leydig).
Development of the stroma
The mesenchyma between the testicular cords congeals and forms connective tissue septa that subdivide the testicles into
lobules (ca. 250-370).
In stage 22 (ca. 53 days) this mesenchyma also forms a taut connective tissue layer between the testicular cords and the
coelomic epithelium as well as the future tunica albuginea. Finally, the coelomic epithelium transforms itself into a mesothelium, just like the coelomic epithelium around the other serous cavities (peritoneum, pleura, pericardium).
Summary:
In the testicular cords PGC (future spermatozoa) are to be found. The somatic cells differentiate themselves into Sertoli's
supporting cells, responsible for nourishing the spermatozoa and secreting the antimüllerian hormone (AMH), which promotes the atrophy of the paramesonephric duct (Müller).
The rete testis forms the continuation of the centrally-lying testicular cords or the straight seminiferous tubules.
The efferent tubules connect the rete testis with the mesonephric duct (Wolff), the future epididymis, which continues with
the deferent duct.
The interstitial mesenchymal cells of the testes develop into Leydig's interstitial cells. They are responsible for the production of testosterone that, among other things, assures that the mesonephric duct (Wolff) does not atrophy.
The stroma, made of connective tissue, subdivides the testes into lobules and forms the tunica albuginea.
The differentiation of the ovaries happens later than that of the testes, taking place during the 8th week 20-23. Since females lack the Y chromosome, they have no SRY gene, except when a translocation of the gene onto the X chromosome
occurs!
Histologically two regions can be distinguished in an ovary:
Cortex, containing all the elements of the parenchyma
Medulla, which shares the elements of the stroma with the cortex.
Development of the ovarium stroma
In an ovary the majority of the gonadal cords stay in contact with the surface coelomic epithelium. Those gonadal cords
that go into the depths out of the thickened coelomic epithelium and lose contact with it atrophy. One also suspects there
are signals from the ovary, though, which actively prevent the differentiation into male gonads. So, for example, WNT-4
functions partly as an anti-testis gene in that it suppresses certain developmental steps of differentiation in the direction of
the testes
Development of the ovarium parenchyma
Towards the end of the embryonic period one can distinguish the cortex with its gonadal cords and the medullar PGC in the
ovary. Although one often finds in the literature that cells with a mesonephric origin are also present in the ovarian stroma,
examinations made on mice ovaries have shown that no cells migrate out of the mesonephros into the ovary (in contrast
with myofibroblasts of the testis. Probably the cells of the mesonephros only reach the hilus area of the ovary and participate there in the weakly formed rete ovarii.
In the course of the 4th month the gonadal cords dissolve - also in the cortex - due to blood vessels that are sprouting from
the medulla and isolated cell accumulations surround the oogonia that increasingly divide synchronously (mitosis). Like the
spermatogonia the oogonia form similar cell clones. The individual cells are connected with each other via cellular bridges.
One can now distinguish various zones in the cortex: In the outermost zone proliferating oogonia are found; somewhat further inward one recognizes oocytes that have spontaneously entered into the prophase of the first meiosis (meiosis 1).
From the 5th month a third zone becomes visible towards the medulla in which the oocytes have already completed the
prophase of the first meiosis and are surrounded by a monolayer of cells that have differentiated out of the gonadal cord
cells and now are now called follicle or granulosa cells. The primary oocytes that are enveloped by follicle cells are now
designated primordial follicles and then remain in this stage of the first meiosis (dictyotene stage).
The gonadal cords in the center of the ovary degenerate and only those that are near the surface epithelium remain.
Through blood vessels that grow into it and connective tissue stroma from the medulla the gonadal cords in the cortex
break up into small cell accumulations. These increasingly surround the PGC and the primary oocytes that also further develop in the cortex.
After approximately the middle of the pregnancy (20th week) the entire cortex is filled uniformly with primordial follicles.
The rete ovarii receives no connection to the mesonephric tubules or the mesonephric duct.
During the early fetal period millions of primordial follicles arise through intensive mitotic divisions of the oogonia (the
follicle stages from primordial follicle to tertiary follicle).
The number of the primordial follicles at birth amount to between 300,000 and 2 million, but they decrease massively from
then till puberty. At the beginning of puberty only ca. 40,000 still remain. Of these only ca. 300 primary oocytes develop
further between puberty and menopause into fertilizable oocytes.
It is to be noted that follicles only form in the presence of the PGC. Without them, sterile gonadal cords are formed that
then further degenerate and as a consequence the ovary then consists only of stroma.
Summary
The development of the ovary is characterized by the following:
Gonadal cords remain in existence only near the cortex; in the medulla they atrophy. The rete ovarii is only rudimentarily
developed. Its cells probably come from the mesonephros, but a connection between the rete testis and the mesonephros
never comes into existence.
Cortical gonadal cords separate themselves from the others in order to make isolated cell accumulations around the oocytes
and thus to form the primordial follicles.
Coelomic epithelium, out of which a simple cubic ovarian mesothelium arises.
Between the 3rd month of pregnancy and its end the testes become transferred from the lumbar area (ventro-medial to the
mesonephros) into the future scrotum. This transfer is due to a combination of growth processes and hormonal influences.
The gubernaculum testis also plays a decisive role in this phenomenon.
The gubernaculum testis arises in the course of the 7th week from the lower gubernaculum, after the mesonephros has atrophied. Cranially it has its origin at the testis and inserts in the region of the genital swelling (future scrotum).
At the same time, at the inguinal canal along the lower gubernaculum, an evagination of the peritoneum arises, the vaginal
process, on which the testes will slide through the inguinal canal.
Between the 3rd and 7th month of pregnancy the testes remain near the inguinal canal in order to pass through it. The vaginal process lengthens while the gubernaculum shortens, thereby drawing the testis, the deferent duct and its vessels on both
sides downwards.
In the 9th month of pregnancy (but also sometimes only after birth) the testes reach the scrotum. The vaginal process forms
now a serous bilaminar structure on the front side of the testis.
In that the vaginal process lengthens downwardly, it takes the muscle fibers of the oblique internal muscle and the transverse muscle with it.
The muscle fascia of the transverse muscle is the innermost layer and in the scrotal region, it forms the internal spermatic
fascia of the spermatic cord and the scrotum.
The muscle layer of the musculus cremaster is formed from fibers of the oblique internal and transverse muscles.
Externally, the external spermatic fascia is formed from the superficial aponeurosis of the oblique external abdominal
muscle.
The region, where the testes pass through the abdominal wall, is called the inguinal canal.
Between the 7th and the 12th week the gubernaculum shortens and pulls the testes, the deferent duct and its vessels downwards.
Between the 3rd and 7th month the testes stay in the area of the inguinal canal so they can enter into it. They reach the
scrotum at roughly the time of birth under the influence of the androgen hormone.
Descent of the testes
While in the first year of life the upper part of the vaginal process becomes obliterated, there remains only the peritoneovaginal ligament. The lower portion persists as the tunica vaginalis testis, which consists of a parietal and a visceral layer.
The ovaries are also moved slightly - from the location where they are engendered in the middle of the abdomen to the pelvis. This migration results partially from the massive growth of the upper abdominal region in comparison with the pelvic
area.
The influence of the lower gubernaculum in this process is not entirely clear.
The mesonephros with the mesonephric duct and the mesonephric structures has atrophied at this time. The various mesos
remain in existence, however.
The mesonephros atrophies in the 7th week. Only the ovary with its mesovarium medially and the paramesonephric duct
(later fallopian tube) with the mesosalpinx lateral to the meso of the original urogenital tract remain. They are connected
with the dorsal abdominal wall of the embryo via the meso of the original urogenital tract.
Displacement of the ovaries
The ovary tips backwards. The fallopian tube, which forms from the cranial part of the paramesonephric duct (Müller), is
pulled medially by the joining of the distal parts of the paramesonephric duct on both sides and thus takes on a horizontal
position.
Through atrophy of the mesonephros the upper gubernaculum connects the ovary directly with the upper rear body wall and
becomes designated as the suspensory ligament of ovary.
The lower gubernaculum has its origin in the bottom side of the ovary and forms the ovarian ligament and, further down,
the round ligament of uterus that reaches the genital swelling (labia majora) through the inguinal canal.
The nephrogenic cord is originally vertical. The fallopian tube, which forms from the upper part of the paramesonephric
duct (Müller), finally takes on a horizontal position in that it is drawn medially by the joining of the lower part of the
paramesonephric duct (Müller) as the uterus is being formed.
The ovary, which initially lies medially to the fallopian tube (paramesonephric duct) in front of the atrophying mesonephros, slides backwards as a result.
Development of the ligaments
The peritoneal mesos passively follow these movements. Finally the broad ligament of uterus forms with three sections:
Upper section: mesosalpinx with the fallopian tube
Ventral section: mesometrium with the round ligament of uterus
Dorsal section: mesovarium with the ovarian ligament.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 10. Development, anatomy and abnormalities of male genital ducts.
The aim: to learn the anatomy and relations of male genital ducts.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, urologists, gynaecologists etc.
Up to the 7th week the internal genital organs in both sexes on both sides consist of two canal systems:
The mesonephric duct and the mesonephric tubules, which first form on the dorsal side of the nephrogenic cord at the level
of the 9th somite in the form of solid, cellular mesenchymal cords. They detach themselves from the nephrogenic cord and
are located below the coelomic epithelium that is thickened at this place. The detailed description of the development of the
mesonephric duct can be found in the urinary system module.
The paramesonephric duct (Müller) is formed from a finger-shaped invagination of the coelomic epithelium on the upper
pole of the mesonephros. It forms here a funnel that opens into the coelomic cavity (future ampulla of the fallopian tube).
The paramesonephric duct invades on both sides - laterally to the mesonephric duct - into the mesonephros and grows in
the caudal direction. At the lower end of the mesonephros the paramesonephric duct crosses over the mesonephric duct in
order to grow further medially. There, the paramesonephric ducts meet on both sides and fuse to form a canal ((the future
uterus).They then push on the urogenital sinus, forming a small protrusion, the paramesonephric tubercle. The differentiation of the male sex organ canals is influenced by the testosterone hormone that is produced from the 8th week in the fetal
testis by Leydig's interstitial cells.
The two ejaculatory ducts as well as the prostatic utricle (which will have a dead end due to the atrophy of the paramesonephric duct) empty into the seminal colliculus.
Two phenomena mark the differentiation of the canals of the internal male sex organs:
The atrophy of the paramesonephric duct (Müller)
The development and differentiation of the mesonephric duct (Wolff)
The mesonephric duct (Wolff) atrophies cranially and leaves behind only the epididymal appendage as an embryonic rudiment. On both sides the parts of the mesonephric duct, which lie across from the testes, form the epididymis. The testis and
the epididymis of both sides are partially enveloped by the tunica vaginalis testis (serous bilaminar membrane with a periorchium [ = outermost layer] and epiorchium [ = inner layer]). In the part of the epididymis are end the efferent ductules.
They originate from the mesonephric tubules, and so form the beginning of the epididym. Immediately afterwards it coils
tightly and finally goes into the lower part of the epididymis (its tail) and over into the deferent duct. This is a musculoepithelial tube that, during ejaculation, dispatches the sperm cells from the epididymis into the urethra.
In the male fetus - between the 8th and 11th week - the paramesonephric duct atrophies due to the effects of the antimüllerian hormone (AMH), which is formed by precursors of Sertol's supporting cells (cells that surround the primordial germ
cells and come from the primitive gonadal cords). Despite the effects of this hormone, embryonic remnants of the
paramesonephric duct remain behind in males. These are the testicular appendage at the cranial pole of the testis and the
prostatic utricle at its caudal pole.
The accessory sexual glands originate from two epithelial tissues. They either come from the epithelial mesodermal origin
of the mesonephric duct (Wolff) or from the epithelial endodermal origin of the urogenital sinus.
The seminal vesicle differentiates itself during the 12th week from a protrusion on the deferent duct, near where it opens at
the back wall of the urogenital sinus (future prostatic part of the urethra). They thus have a mesodermal origin. These
paired glands produce a viscous, fructose-rich secretion that serves as a source of energy for the sperm cells. The portion of
the mesonephric duct that lies between the junction of the seminal vesicle and the prostatic part of the urethra is called the
ejaculatory duct. Between the two ejaculatory duct junctions the prostatic utricle (remainder of the paramesonephric duct)
has its opening. This location is called the seminal colliculus.
The prostate develops from a protrusion on the dorsal wall of the prostatic part of the urethra during the 12th week. The
prostate's glandular epithelium develops, therefore, from cells that have their origin in the endoderm, while the stroma and
smooth muscle develops from cells with a mesodermal origin - under the inducing influence of DHT (see: hormonal factors
in sex differentiation). The glands become active after the 15th week and surround the two ejaculatory ducts and the prostatic utricle as well as the prostatic part of the urethra.
Over the course of the 12th week and parallel to the development of the prostate, bulbourethral (Cowper's) and urethral
(Littre's) glands form, originating in pairs of endodermal protrusions of the spongy part of the urethra, which follow from
the prostatic membranous parts. Finally, the seminal fluid is augmented by secretions from the seminal vesicle, the prostate,
the bulbourethral and urethral glands.
In studies of the urinary system we have seen that the cloaca is subdivided by the uro-rectal septum into the rectum (dorsal)
and the primary urogenital sinus (ventral).
The primitive urogenital sinus is in contact with the allantois. The upper part forms the future urinary bladder, while the
middle and lower part forms the definitive urogenital sinus and, from it, the pelvic and phallic parts of the urethra (stage
17).
The uro-rectal septum has subdivided the cloaca into the primary urogenital sinus (ventrally) and the rectum (dorsally).
Out of the primary urogenital sinus arise the urinary bladder and the definitive urogenital sinus.
The pelvic part of the definitive urogenital sinus forms the prostatic and membranous parts of the urethra, the phallic part of
the definitive urogenital sinus, the spongy part of the urethra and the urethral vestibule.
Around the 4th month an epithelial cord grows on the glans penis - into the depths - and binds it with the spongy part of
the urethra.
The spongy part of the urethra comes to a dead end in the outer section of the penis. Only in the 4th month does an epithelial lamella form from the tip of the penis to the blind end of the urethra. From this arises the urethra within the glans.
Summary:
From the mesonephric duct (Wolff) arise:
Epididymis
Deferent duct
Seminal vesicle
Ejaculatory duct
From the endoderm of the urogenital sinus arise:
Urinary bladder
Out of the pelvic part of the definitive urogenital sinus: the prostatic and membranous parts of the urethra, the prostate and
the bulbourethral gland (Cowper's).
Out of the phallic part of the definitive urogenital sinus: the spongy part of the urethra and the urethral glands (Littre's)
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 11. Development, anatomy and abnormalities of female genital ducts.
The aim: to learn the anatomy and relations of female genital ducts.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, gynaeologists, obstetritians etc.
During the 7th week the canal system of the female sex organs differentiates. The mesonephric duct and its tubules atrophy
and out of the paramesonephric duct (Müller) arises the future fallopian tube, the uterus and the upper part of the vagina.
Sometimes, a few embryonic remnants of the mesonephric duct remain in the form of the epoöphoron, the paroöphoron at
the level of the mesovarium, and a row of small cysts of Gartner.
Out of the upper, non-fused portion of the paramesonephric duct (Müller) arises the fallopian tube and its ampulla. The
lower section fuses after it crosses medially on both sides of the inferior ovarian gubernaculum and forms the utero-vaginal
canal. The medial septum in between disappears at the end of the 3rd month.
To be observed is the development of the ligaments. The ovarian gubernaculum gets attached on the developing uterovaginal canal there where it goes over into the fallopian tube. Above it forms the ovarian ligament and below the round
ligament of uterus, which goes through the inguinal canal and inserts in the female genital swelling (labia majora).
If the separating wall beyond the fusion location of the two paramesonephric ducts is not resorbed, various utero-vaginal
abnormalities result.
Up to the 7th week two canal systems on each side exist in both sexes. In the 8th week the paramesonephric ducts (Müller)
fuse in the lower portion after they have crossed medially on both sides of the mesonephric duct (Wolff).
At the end of the 3rd month the separating wall dissolves in the uterus and the vagina. The uterus lengthens in that the solid
lower end of the paramesonephric duct stretches in a downward direction and is subsequently canalized. Out of the lower
section arises the upper part of the vagina. It joins with the vaginal lamina, which arises from the urogenital sinus and
forms the lower portion of the vagina.
The blind end of the utero-vaginal canal forms the sinu-vaginal eminence 22 and ends at the back wall of the urogenital
sinus (SUG).
The sinu-vaginal eminence becomes thicker due to epithelial proliferation and retracts, while the wall of the SUG also
thickens there. These epithelial layers, which form at the lower end of the utero-vaginal canal, are known as the vaginal
plate. At their cranial end they form a circular protrusion, the location of the future vaginal fornix.
This sinu-vaginal eminence becomes thicker due to epithelial proliferation. This also leads to a epithelial proliferation in
the SUG epithelium. Together they form the vaginal plate.
Through canalization of the vaginal plate the utero-vaginal canal opens itself towards the outside. The upper 3/4 of the
vagina comes from the mesoderm and the lower fourth from the endoderm.
The fibromuscular walling forms from the neighboring mesenchyma. The vagina is separated from the SUG by the hymen.
Its origin is not entirely clear. Discussed is a passive invagination of the back wall of the SUG.
The accessory glands arise from the endoderm of the SUG:
The greater vestibular glands (Bartholini) are paired glands that form in the course of the 12th week from the endoderm of
the SUG. The outflow canals empty sideways in the vaginal vestibule. They correspond to the bulbourethral gland (Cowper) in males.
The lesser vestibular glands (Skene) or paraurethral glands also form from epithelial buds (endoderm) of the SUG and grow
into the neighboring mesenchyma. They are distributed over the whole vaginal vestibule and - in males - correspond to the
prostate.
In females the cranial portion of the pelvic part of the definitive SUG remain narrow and forms the female urethra, which is
very short.
With the progressing development the caudal portion of the pelvic part shrinks and becomes included in the phallic part
(vaginal vestibule). Therein discharge the urethra and the vagina.
The phallic part of the definitive SUG enlarges to become the vaginal vestibule that is caudally closed off externally by the
urogenital membrane. It then tears in the course of the 7th week 19.
Summary:
From the paramesonephric duct (Müller) arises:
Uterus
Fallopian tube
Vagina (3/4)
From the SUG endoderm arises:
Vagina (1/4)
Urethra
Vaginal vestibule
Urethral glands, para-urethral and vestibular
Summary: Development of the internal genital organs
In males the internal sex organs come from the mesonephric duct (Wolff) that differentiates itself into the epididymis, deferent duct, seminal vesicle and the ejaculatory duct. The paramesonephric duct (Müller) atrophies. It leaves behind embryonic remnants such as the testicular appendage (hydatid) and parts of the prostatic utricule.
In females the paramesonephric duct (Müller) remains in existence and differentiates itself into the fallopian tube with its
ampullae and, following its fusion at the caudal end, into the uterus and the upper part of the vagina. The mesonephric duct
(Wolff) with its tubules atrophies and leaves embryonic remnants such as the ductus longitudinalis epoöphori (Gartner),
epoöphoron and paroöphoron.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 12. Classification, anatomy, function of endocrine system.
The aim: to learn the classification, anatomy, function of endocrine.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, endocrinologists etc.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 13. Classification, anatomy of immune system.
The aim: to learn the anatomy and relations of immune system.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, allergologists etc.
The thymus is a temporary organ, attaining its largest size at the time of puberty (Hammar), when it ceases to grow, gradually dwindles, and almost disappears. If examined when its growth is most active, it will be found to consist of two lateral
lobes placed in close contact along the middle line, situated partly in the thorax, partly in the neck, and extending from the
fourth costal cartilage upward, as high as the lower border of the thyroid gland. It is covered by the sternum, and by the
origins of the Sternohyoidei and Sternothyreoidei. Below, it rests upon the pericardium, being separated from the aortic
arch and great vessels by a layer of fascia. In the neck it lies on the front and sides of the trachea, behind the Sternohyoidei
and Sternothyreoidei. The two lobes generally differ in size; they are occasionally united, so as to form a single mass; and
sometimes separated by an intermediate lobe. The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces. It is
about 5 cm. in length, 4 cm. in breadth below, and about 6 mm. in thickness. At birth it weighs about 15 grams, at puberty
it weighs about 35 grams; after this it gradually decreases to 25 grams at twentyfive years, less than 15 grams at sixty, and
about 6 grams at seventy years.
Development. - The thymus appears in the form of two flask-shaped entodermal diverticula, which arise, one on either side,
from the third branchial pouch, and extend lateralward and backward into the surrounding mesoderm in front of the ventral
aortae. Here they meet and become joined to one another by connective tissue, but there is never any fusion of the thymus
tissue proper. The pharyngeal opening of each diverticulum is soon obliterated, but the neck of the flask persists for some
time as a cellular cord. By further proliferation of the cells lining the flask, buds of cells are formed, which become surrounded and isolated by the invading mesoderm. In the latter, numerous lymphoid cells make their appearance, and are
agregated to form lymphoid follicles. These lymphoid cells are probably derivatives of the entodermal cells which lined the
original diverticula and their subdivisions. Additional portions of thymus tissue are sometimes developed from the fourth
branchial pouches. Thymus continues to grow until the time of puberty and then begins to atrophy.
UNIT 10. NERVES AND VESSELS OF INTERNAL ORGANS
AND BODY CAVITIES.
Practice class 22. Written tests and examination of practice skills on urogenital and endocrine
system. Examination of self-taught tasks. Review of vegetative system.
Differences between vegetative and somatic nervous system
Distinguishing feature
Somatic nervous system
Innervation region
Skeletal (striated) muscles
Principles of centers distribution - segmental
and nerves exit
- uniform
The way of connection with the
innervated organ
Distribution of cellular component
in CNS
Size of neuron bodies
Fiber structure
Fiber diameter
Impulse conduction rate
Character of interneuronal relation
Axons emerge from the anterior spinal roots and reach the skeletal muscles without interruptions
Synapses and cellular bodies concentrate in CNS
Variety of neuron shapes and types,
100 to 200 µm
Myelinated
12-14 µm
0,3-10 m/sec
Complex relation, plexuses are infrequenr
Vegetative nervous system
Heart, smooth muscles, glands
-focal
а) mesencephalic portion
б) bulbar portion
в) thoracolumbar portion
г) sacral portion
The rule of obligatory monophase interruption (the rule of Lenglev), pre- and
postganglionic fibers
Distribution is more even
Less various, 30-60µm
Postganglionic fibers are non-myelinated
1-1,3 µm– non-myelinated fibers
1,5-4,5 µm – myelinated fibers
12-100 m/sec
More ordinary and monotonous relations,
strong tendency to plexus forming
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 23. General characteristic of vegetative nervous system. Parasympathetic nervous
system. Its central and peripheral parts. Vagal nerve.
The aim: to learn the anatomy and relations of parasympathetic part of vegetative nervous system.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The vagus nerve is composed of both motor and sensory fibers, and has a more extensive course and distribution than any
of the other cranial nerves, since it passes through the neck and thorax to the abdomen.
The vagus is attached by eight or ten filaments to the medulla oblongata in the groove between the olive and the inferior
peduncle, below the glossopharyngeal. The sensory fibers arise from the cells of the jugular ganglion and ganglion
nodosum of the nerve, and, when traced into the medulla oblongata mostly end by arborizing around the cells of the inferior
part of a nucleus which lies beneath the ala cinerea in the lower part of the rhomboid fossa. These are the sympathetic afferent fibers. Some of the sensory fibers of the glossopharyngeal nerve have been seen to end in the upper part of this nucleus. A few of the sensory fibers of the vagus, probably taste fibers, descend in the fasciculus solitarius and end around its
cells. The somatic sensory fibers, few in number, from the posterior part of the external auditory meatus and the back of the
ear, probably join the spinal tract of the trigeminal as it descends in the medulla. The somatic motor fibers arise from the
cells of the nucleus ambiguus, already referred to in connection with the motor root of the glossopharyngeal nerve.
The sympathetic efferent fibers, distributed probably as preganglionic fibers to the thoracic and abdominal viscera, i. e., as
motor fibers to the bronchial tree, inhibitory fibers to the heart, motor fibers to the esophagus, stomach, small intestine and
gall passages, and as secretory fibers to the stomach and pancreas, arise from the dorsal nucleus of the vagus.
The filaments of the nerve unite, and form a flat cord, which passes beneath the flocculus to the jugular foramen, through
which it leaves the cranium. In emerging through this opening, the vagus is accompanied by and contained in the same
sheath of dura mater with the accessory nerve, a septum separating them from the glossopharyngeal which lies in front. In
this situation the vagus presents a well-marked ganglionic enlargement, which is called the jugular ganglion (ganglion of
the root); to it the accessory nerve is connected by one or two filaments. After its exit from the jugular foramen the vagus is
joined by the cranial portion of the accessory nerve, and enlarges into a second gangliform swelling, called the ganglion
nodosum (ganglion of the trunk); through this the fibers of the cranial portion of the accessory pass without interruption,
being principally distributed to the pharyngeal and superior laryngeal branches of the vagus, but some of its fibers descend
in the trunk of the vagus, to be distributed with the recurrent nerve and probably also with the cardiac nerves.
The vagus nerve passes vertically down the neck within the carotid sheath, lying between the internal jugular vein and
internal carotid artery as far as the upper border of the thyroid cartilage, and then between the same vein and the common
carotid artery to the root of the neck. The further course of the nerve differs on the two sides of the body.
On the right side, the nerve passes across the subclavian artery between it and the right innominate vein, and descends by
the side of the trachea to the back of the root of the lung, where it spreads out in the posterior pulmonary plexus. From the
lower part of this plexus two cords descend on the esophagus, and divide to form, with branches from the opposite nerve,
the esophageal plexus. Below, these branches are collected into a single cord, which runs along the back of the esophagus
enters the abdomen, and is distributed to the postero-inferior surface of the stomach, joining the left side of the celiac plexus, and sending filaments to the lienal plexus.
On the left side, the vagus enters the thorax between the left carotid and subclavian arteries, behind the left innominate
vein. It crosses the left side of the arch of the aorta, and descends behind the root of the left lung, forming there the posterior pulmonary plexus. From this it runs along the anterior surface of the esophagus, where it unites with the nerve of the
right side in the esophageal plexus, and is continued to the stomach, distributing branches over its anterosuperior surface;
some of these extend over the fundus, and others along the lesser curvature. Filaments from these branches enter the lesser
omentum, and join the hepatic plexus.
The Jugular Ganglion (ganglion jugulare; ganglion of the root) is of a grayish color, spherical in form, about 4 mm. in
diameter.
Branches of Communication. - This ganglion is connected by several delicate filaments to the cranial portion of the accessory nerve; it also communicates by a twig with the petrous ganglion of the glossopharyngeal, with the facial nerve by
means of its auricular branch, and with the sympathetic by means of an ascending filament from the superior cervical ganglion.
The Ganglion Nodosum (ganglion of the trunk; inferior ganglion) is cylindrical in form, of a reddish color, and 2.5 cm. in
length. Passing through it is the cranial portion of the accessory nerve, which blends with the vagus below the ganglion.
Branches of Communication. - This ganglion is connected with the hypoglossal, the superior cervical ganglion of the sympathetic, and the loop between the first and second cervical nerves.
Branches of Distribution. - The branches of distribution of the vagus are:
In the Jugular Fossa…
Meningeal.
Auricular.
In the Neck…………
In the Thorax……….
In the Abdomen…….
Pharyngeal.
Superior laryngeal.
Recurrent.
Superior cardiac.
Inferior cardiac.
Anterior bronchial.
Posterior bronchial.
Esophageal.
Gastric.
Celiac.
Hepatic.
The Meningeal Branch (ramus meningeus; dural branch) is a recurrent filament given off from the jugular ganglion; it is
distributed to the dura mater in the posterior fossa of the base of the skull.
The Auricular Branch (ramus auricularis; nerve of Arnold) arises from the jugular ganglion, and is joined soon after its
origin by a filament from the petrous ganglion of the glossopharyngeal; it passes behind the internal jugular vein, and enters
the mastoid canaliculus on the lateral wall of the jugular fossa. Traversing the substance of the temporal bone, it crosses the
facial canal about 4 mm. above the stylomastoid foramen, and here it gives off an ascending branch which joins the facial
nerve. The nerve reaches the surface by passing through the tympanomastoid fissure between the mastoid process and the
tympanic part of the temporal bone, and divides into two branches: one joins the posterior auricular nerve, the other is distributed to the skin of the back of the auricula and to the posterior part of the external acoustic meatus.
The Pharyngeal Branch (ramus pharyngeus), the principal motor nerve of the pharynx, arises from the upper part of the
ganglion nodosum, and consists principally of filaments from the cranial portion of the accessory nerve. It passes across the
internal carotid artery to the upper border of the Constrictor pharyngis medius, where it divides into numerous filaments,
which join with branches from the glossopharyngeal, sympathetic, and external laryngeal to form the pharyngeal plexus.
From the plexus, branches are distributed to the muscles and mucous membrane of the pharynx and the muscles of the soft
palate, except the Tensor veli palatini. A minute filament descends and joins the hypoglossal nerve as it winds around the
occipital artery.
The Superior Laryngeal Nerve (n. laryngeus superior) larger than the preceding, arises from the middle of the ganglion
nodosum and in its course receives a branch from the superior cervical ganglion of the sympathetic. It descends, by the side
of the pharynx, behind the internal carotid artery, and divides into two branches, external and internal.
The external branch (ramus externus), the smaller, descends on the larynx, beneath the Sternothyreoideus, to supply the
Cricothyreoideus. It gives branches to the pharyngeal plexus and the Constrictor pharyngis inferior, and communicates with
the superior cardiac nerve, behind the common carotid artery.
The internal branch (ramus internus) descends to the hyothyroid membrane, pierces it in company with the superior laryngeal artery, and is distributed to the mucous membrane of the larynx. Of these branches some are distributed to the epiglottis, the base of the tongue, and the epiglottic glands; others pass backward, in the aryepiglottic fold, to supply the mucous
membrane surrounding the entrance of the larynx, and that lining the cavity of the larynx as low down as the vocal folds. A
filament descends beneath the mucous membrane on the inner surface of the thyroid cartilage and joins the recurrent nerve.
The Recurrent Nerve (n. recurrens; inferior or recurrent laryngeal nerve) arises, on the right side, in front of the subclavian
artery; winds from before backward around that vessel, and ascends obliquely to the side of the trachea behind the common
carotid artery, and either in front of or behind the inferior thyroid artery. On the left side, it arises on the left of the arch of
the aorta, and winds below the aorta at the point where the ligamentum arteriosum is attached, and then ascends to the side
of the trachea. The nerve on either side ascends in the groove between the trachea and esophagus, passes under the lower
border of the Constrictor pharyngis inferior, and enters the larynx behind the articulation of the inferior cornu of the thyroid
cartilage with the cricoid; it is distributed to all the muscles of the larynx, excepting the Cricothyreoideus. It communicates
with the internal branch of the superior laryngeal nerve, and gives off a few filaments to the mucous membrane of the lower
part of the larynx.
As the recurrent nerve hooks around the subclavian artery or aorta, it gives off several cardiac filaments to the deep part of
the cardiac plexus. As it ascends in the neck it gives off branches, more numerous on the left than on the right side, to the
mucous membrane and muscular coat of the esophagus; branches to the mucous membrane and muscular fibers of the trachea; and some pharyngeal filaments to the Constrictor pharyngis inferior.
The Superior Cardiac Branches (rami cardiaci superiores; cervical cardiac branches), two or three in number, arise from
the vagus, at the upper and lower parts of the neck.
The upper branches are small, and communicate with the cardiac branches of the sympathetic. They can be traced to the
deep part of the cardiac plexus.
The lower branch arises at the root of the neck, just above the first rib. That from the right vagus passes in front or by the
side of the innominate artery, and proceeds to the deep part of the cardiac plexus; that from the left runs down across the
left side of the arch of the aorta, and joins the superficial part of the cardiac plexus.
The Inferior Cardiac Branches (rami cardiaci inferiores; thoracic cardiac branches), on the right side, arise from the trunk
of the vagus as it lies by the side of the trachea, and from its recurrent nerve; on the left side from the recurrent nerve only;
passing inward, they end in the deep part of the cardiac plexus.
The Anterior Bronchial Branches (rami bronchiales anteriores; anterior or ventral pulmonary branches), two or three in
number, and of small size, are distributed on the anterior surface of the root of the lung. They join with filaments from the
sympathetic, and form the anterior pulmonary plexus.
The Posterior Bronchial Branches (rami bronchiales posteriores; posterior or dorsal pulmonary branches), more numerous
and larger than the anterior, are distributed on the posterior surface of the root of the lung; they are joined by filaments
from the third and fourth (sometimes also from the first and second) thoracic ganglia of the sympathetic trunk, and form the
posterior pulmonary plexus. Branches from this plexus accompany the ramifications of the bronchi through the substance
of the lung.
The Esophageal Branches (rami aesophagei) are given off both above and below the bronchial branches; the lower are
numerous and larger than the upper. They form, together with the branches from the opposite nerve, the esophageal plexus.
From this plexus filaments are distributed to the back of the pericardium.
The Gastric Branches (rami gastrici) are distributed to the stomach. The right vagus forms the posterior gastric plexus on
the postero-inferior surface of the stomach and the left the anterior gastric plexus on the antero-superior surface.
The Celiac Branches (rami caeliaci) are mainly derived from the right vagus: they join the celiac plexus and through it
supply branches to the pancreas, spleen, kidneys, suprarenal bodies, and intestine.
The Hepatic Branches (rami hepatici) arise from the left vagus: they join the hepatic plexus and through it are conveyed to
the liver.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 24. Sympathetic nervous system. Its central and peripheral parts. Sympathetic
trunk, branches of ganglions.
The aim: to learn the anatomy and relations of the sympathetic part of autonomous nervous system.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, neurologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The sympathetic nervous system innervates all the smooth muscles and the various glands of the body, and the striated
muscle of the heart. The efferent sympathetic fibers which leave the central nervous system in connection with certain of
the cranial and spinal nerves all end in sympathetic ganglia and are known as preganglionic fibers. From these ganglia
postganglionic fibers arise and conduct impulses to the different organs. In addition, afferent or sensory fibers connect
many of these structures with the central nervous system.
The peripheral portion of the sympathetic nervous system is characterized by the presence of numerous ganglia and complicated plexuses. These ganglia are connected with the central nervous system by three groups of sympathetic efferent or
preganglionic fibers, i. e., the cranial, the thoracolumbar, and the sacral. These outflows of sympathetic fibers are separated
by intervals where no connections exist. The cranial and sacral sympathetics are often grouped together owing to the resemblance between the reactions produced by stimulating them and by the effects of certain drugs. Acetyl-choline, for example, when injected intravenously in very small doses, produces the same effect as the stimulation of the cranial or sacral
sympathetics, while the introduction of adrenalin produces the same effect as the stimulation of the thoracolumbar sympathetics. Much of our present knowledge of the sympathetic nervous system has been acquired through the application of
various drugs, especially nicotine which paralyzes the connections or synapses between the preganglionic and postganglionic fibers of the sympathetic nerves. When it is injected into the general circulation all such synapses are paralyzed; when
it is applied locally on a ganglion only the synapses occurring in that particular ganglion are paralyzed.
The Cranial Sympathetics - The cranial sympathetics include sympathetic efferent fibers in the oculomotor, facial, glossopharyngeal and vagus nerves, as well as sympathetic afferent in the last three nerves.
The Sympathetic Efferent Fibers of the Oculomotor Nerve probably arise from cells in the anterior part of the oculomotor
nucleus which is located in the tegmentum of the mid-brain. These preganglionic fibers run with the third nerve into the
orbit and pass to the ciliary ganglion where they terminate by forming synapses with sympathetic motor neurons whose
axons, postganglionic fibers, proceed as the short ciliary nerves to the eyeball. Here they supply motor fibers to the Ciliaris
muscle and the Sphincter pupillae muscle. So far as known there are no sympathetic afferent fibers connected with the
nerve.
The Sympathetic Efferent Fibers of the Facial Nerve are supposed to arise from the small cells of the facial nucleus. According to some authors the fibers to the salivary glands arise from a special nucleus, the superior salivatory nucleus, consisting of cells scattered in the reticular formation, dorso-medial to the facial nucleus. These preganglionic fibers are distributed partly through the chorda tympani and lingual nerves to the submaxillary ganglion where they terminate about the
cell bodies of neurons whose axons as postganglionic fibers conduct secretory and vasodilotar impulses to the submaxillary
and sublingual glands. Other preganglionic fibers of the facial nerve pass via the great superficial petrosal nerve to the
sphenopalatine ganglion where they form synapses with neurons whose postganglionic fibers are distributed with the superior maxillary nerve as vasodilator and secretory fibers to the mucous membrane of the nose, soft palate, tonsils, uvula, roof
of the mouth, upper lips and gums, parotid and orbital glands.
There are supposed to be a few sympathetic afferent fibers connected with the facial nerve, whose cell bodies lie in the
geniculate ganglion, but very little is known about them.
The Sympathetic Afferent Fibers of the Glossopharyngeal Nerve are supposed to arise either in the dorsal nucleus (nucleus ala cinerea) or in a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. These preganglionic
fibers pass into the tympanic branch of the glossopharyngeal and then with the small superficial petrosal nerve to the otic
ganglion. Postganglionic fibers, vasodilator and secretory fibers, are distributed to the parotid gland, to the mucous membrane and its glands on the tongue, the floor of the mouth, and the lower gums.
Sympathetic Afferent Fibers, whose cells of origin lie in the superior or inferior ganglion of the trunk, are supposed to
terminate in the dorsal nucleus. Very little is known of the peripheral distribution of these fibers.
The Sympathetic Efferent Fibers of the Vagus Nerve are supposed to arise in the dorsal nucleus (nucleus ala cinerea).
These preganglionic fibers are all supposed to end in sympathetic ganglia situated in or near the organs supplied by the vagus sympathetics. The inhibitory fibers to the heart probably terminate in the small ganglia of the heart wall especially the
atrium, from which inhibitory postganglionic fibers are distributed to the musculature. The preganglionic motor fibers to
the esophagus, the stomach, the small intestine, and the greater part of the large intestine are supposed to terminate in the
plexuses of Auerbach, from which postganglionic fibers are distributed to the smooth muscles of these organs. Other fibers
pass to the smooth muscles of the bronchial tree and to the gall-bladder and its ducts. In addition the vagus is believed to
contain secretory fibers to the stomach and pancreas. It probably contains many other efferent fibers than those enumerated
above.
Sympathetic Afferent Fibers of the Vagus, whose cells of origin lie in the jugular ganglion or the ganglion nodosum,
probably terminate in the dorsal nucleus of the medulla oblongata or according to some authors in the nucleus of the tractus
solitarius. Peripherally the fibers are supposed to be distributed to the various organs supplied by the sympathetic efferent
fibers.
The Sacral Sympathetics - The Sacral Sympathetic Efferent Fibers leave the spinal cord with the anterior roots of the second, third and fourth sacral nerves. These small medullated preganglionic fibers are collected together in the pelvis into the
nervus erigentes or pelvic nerve which proceeds to the hypogastric or pelvic plexuses from which postganglionic fibers are
distributed to the pelvic viscera. Motor fibers pass to the smooth muscle of the descending colon, rectum, anus and bladder.
Vasodilators are distributed to these organs and to the external genitalia, while inhibitory fibers probably pass to the smooth
muscles of the external genitalia. Afferent sympathetic fibers conduct impulses from the pelvic viscera to the second, third
and fourth sacral nerves. Their cells of origin lie in the spinal ganglia.
The Thoracolumbar Sympathetics - The thoracolumbar sympathetic fibers arise from the dorso-lateral region of the anterior
column of the gray matter of the spinal cord and pass with the anterior roots of all the thoracic and the upper two or three
lumbar spinal nerves. These preganglionic fibers enter the white rami communicantes and proceed to the sympathetic trunk
where many of them end in its ganglia, others pass to the prevertebral plexuses and terminate in its collateral ganglia. The
postganglionic fibers have a wide distribution. The vasoconstrictor fibers to the bloodvessels of the skin of the trunk and
limbs, for example, leave the spinal cord as preganglionic fibers in all the thoracic and the upper two or three lumbar spinal
nerves and terminate in the ganglia of the sympathetic trunk, either in the ganglion directly connected with its ramus or in
neighboring ganglia. Postganglionic fibers arise in these ganglia, pass through gray rami communicantes to all the spinal
nerves, and are distributed with their cutaneous branches, ultimately leaving these branches to join the small arteries. The
postganglionic fibers do not necessarily return to the same spinal nerves which contain the corresponding preganglionic
fibers. The vasoconstrictor fibers to the head come from the upper thoracic nerves, the preganglionic fibers end in the superior cervical ganglion. The postganglionic fibers pass through the internal carotid nerve and branch from it to join the sensory branches of the various cranial nerves, especially the trigeminal nerve; other fibers to the deep structures and the salivary glands probably accompany the arteries.
The postganglionic vasoconstrictor fibers to the bloodvessels of the abdominal viscera arise in the prevertebral or collateral ganglia in which terminate many preganglionic fibers. Vasoconstrictor fibers to the pelvic viscera arise from the inferior mesenteric ganglia.
The pilomotor fibers to the hairs and the motor fibers to the sweat glands apparently have a distribution similar to that of
the vasoconstrictors of the skin.
A vasoconstrictor center has been located by the physiologists in the neighborhood of the facial nucleus. Axons from its
cells are supposed to descend in the spinal cord to terminate about cell bodies of the preganglionic fibers located in the
dorsolateral portion of the anterior column of the thoracic and upper lumbar region.
The motor supply to the dilator pupillae muscle of the eye comes from preganglionic sympathetic fibers which leave the
spinal cord with the anterior roots of the upper thoracic nerves. These fibers pass to the sympathetic trunk through the white
rami communicantes and terminate in the superior cervical ganglion. Postganglionic fibers from the superior cervical ganglion pass through the internal carotid nerve and the ophthalmic division of the trigeminal nerve to the orbit where the long
ciliary nerves conduct the impulses to the eyeball and the dilator pupillae muscle. The cell bodies of these preganglionic
fibers are connected with fibers which descend from the mid-brain.
Other postganglionic fibers from the superior cervical ganglion are distributed as secretory fibers to the salivary glands,
the lacrimal glands and to the small glands of the mucous membrane of the nose, mouth and pharynx.
The thoracic sympathetics supply accelerator nerves to the heart. They are supposed to emerge from the spinal cord in the
anterior roots of the upper four or five thoracic nerves and pass with the white rami to the first thoracic ganglion, here some
terminate, others pass in the ansa subclavia to the inferior cervical ganglion. The postganglionic fibers pass from these ganglia partly through the ansa subclavia to the heart, on their way they intermingle with sympathetic fibers from the vagus to
form the cardiac plexus.
Inhibitory fibers to the smooth musculature of the stomach, the small intestine and most of the large intestine are supposed
to emerge in the anterior roots of the lower thoracic and upper lumbar nerves. These fibers pass through the white rami and
sympathetic trunk and are conveyed by the splanchnic nerves to the prevertebral plexus where they terminate in the collateral ganglia. From the celiac and superior mesenteric ganglia postganglionic fibers (inhibitory) are distributed to the stomach, the small intestine and most of the large intestine. Inhibitory fibers to the descending colon, the rectum and Internal
sphincter ani are probably postganglionic fibers from the inferior mesenteric ganglion.
The thoracolumbar sympathetics are characterized by the presence of numerous ganglia which may be divided into two
groups, central and collateral.
The central ganglia are arranged in two vertical rows, one on either side of the middle line, situated partly in front and
partly at the sides of the vertebral column. Each ganglion is joined by intervening nervous cords to adjacent ganglia so that
two chains, the sympathetic trunks, are formed. The collateral ganglia are found in connection with three great prevertebral
plexuses, placed within the thorax, abdomen, and pelvis respectively.
The sympathetic trunks (truncus sympathicus; gangliated cord) extend from the base of the skull to the coccyx. The cephalic end of each is continued upward through the carotid canal into the skull, and forms a plexus on the internal carotid
artery; the caudal ends of the trunks converge and end in a single ganglion, the ganglion impar, placed in front of the coccyx. The ganglia of each trunk are distinguished as cervical, thoracic, lumbar, and sacral and, except in the neck, they
closely correspond in number to the vertebrae. They are arranged thus:
Cervical portion 3 ganglia
Thoracic portion 12 ganglia
Lumbar portion 4 ganglia
Sacral portion 4 or 5 ganglia
In the neck the ganglia lie in front of the transverse processes of the vertebrae; in the thoracic region in front of the heads
of the ribs; in the lumbar region on the sides of the vertebral bodies; and in the sacral region in front of the sacrum.
Connections with the Spinal Nerves. - Communications are established between the sympathetic and spinal nerves through
what are known as the gray and white rami communicantes; the gray rami convey sympathetic fibers into the spinal nerves
and the white rami transmit spinal fibers into the sympathetic. Each spinal nerve receives a gray ramus communicans from
the sympathetic trunk, but white rami are not supplied by all the spinal nerves. White rami are derived from the first thoracic to the first lumbar nerves inclusive, while the visceral branches which run from the second, third, and fourth sacral
nerves directly to the pelvic plexuses of the sympathetic belong to this category. The fibers which reach the sympathetic
through the white rami communicantes are medullated; those which spring from the cells of the sympathetic ganglia are
almost entirely non-medullated.
The three great gangliated plexuses (collateral ganglia) are situated in front of the vertebral column in the thoracic, abdominal, and pelvic regions, and are named, respectively, the cardiac, the solar or epigastric, and the hypogastric plexuses.
They consist of collections of nerves and ganglia; the nerves being derived from the sympathetic trunks and from the cerebrospinal nerves. They distribute branches to the viscera.
Development. - The ganglion cells of the sympathetic system are derived from the cells of the neural crests. As these crests
move forward along the sides of the neural tube and become segmented off to form the spinal ganglia, certain cells detach
themselves from the ventral margins of the crests and migrate toward the sides of the aorta, where some of them are
grouped to form the ganglia of the sympathetic trunks, while others undergo a further migration and form the ganglia of the
prevertebral and visceral plexuses. The ciliary, sphenopalatine, otic, and submaxillary ganglia which are found on the
branches of the trigeminal nerve are formed by groups of cells which have migrated from the part of the neural crest which
gives rise to the semilunar ganglion. Some of the cells of the ciliary ganglion are said to migrate from the neural tube along
the oculomotor nerve.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 25. Sympathetic trunk, vegetative plexuses.
The aim: to learn the anatomy and relations of the sympathetic trunk and vegetative neural plexuses.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, neurologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The great plexuses of the sympathetic are aggregations of nerves and ganglia, situated in the thoracic, abdominal, and pelvic cavities, and named the cardiac, celiac, and hypogastric plexuses. They consist not only of sympathetic fibers derived
from the ganglia, but of fibers from the medulla spinalis, which are conveyed through the white rami communicantes. From
the plexuses branches are given to the thoracic, abdominal, and pelvic viscera.
The Cardiac Plexus (Plexus Cardiacus) - The cardiac plexus is situated at the base of the heart, and is divided into a superficial part, which lies in the concavity of the aortic arch, and a deep part, between the aortic arch and the trachea. The two
parts are, however, closely connected.
The superficial part of the cardiac plexus lies beneath the arch of the aorta, in front of the right pulmonary artery. It is
formed by the superior cardiac branch of the left sympathetic and the lower superior cervical cardiac branch of the left vagus. A small ganglion, the cardiac ganglion of Wrisberg, is occasionally found connected with these nerves at their point of
junction. This ganglion, when present, is situated immediately beneath the arch of the aorta, on the right side of the ligamentum arteriosum. The superficial part of the cardiac plexus gives branches (a) to the deep part of the plexus; (b) to the
anterior coronary plexus; and (c) to the left anterior pulmonary plexus.
The deep part of the cardiac plexus is situated in front of the bifurcation of the trachea, above the point of division of the
pulmonary artery, and behind the aortic arch. It is formed by the cardiac nerves derived from the cervical ganglia of the
sympathetic, and the cardiac branches of the vagus and recurrent nerves. The only cardiac nerves which do not enter into
the formation of the deep part of the cardiac plexus are the superior cardiac nerve of the left sympathetic, and the lower of
the two superior cervical cardiac branches from the left vagus, which pass to the superficial part of the plexus.
The branches from the right half of the deep part of the cardiac plexus pass, some in front of, and others behind, the right
pulmonary artery; the former, the more numerous, transmit a few filaments to the anterior pulmonary plexus, and are then
continued onward to form part of the anterior coronary plexus; those behind the pulmonary artery distribute a few filaments
to the right atrium, and are then continued onward to form part of the posterior coronary plexus.
The left half of the deep part of the plexus is connected with the superficial part of the cardiac plexus, and gives filaments
to the left atrium, and to the anterior pulmonary plexus, and is then continued to form the greater part of the posterior coronary plexus.
The Posterior Coronary Plexus (plexus coronarius posterior; left coronary plexus) is larger than the anterior, and accompanies the left coronary artery; it is chiefly formed by filaments prolonged from the left half of the deep part of the cardiac
plexus, and by a few from the right half. It gives branches to the left atrium and ventricle.
The Anterior Coronary Plexus (plexus coronarius anterior; right coronary plexus) is formed partly from the superficial and
partly from the deep parts of the cardiac plexus. It accompanies the right coronary artery, and gives branches to the right
atrium and ventricle.
The Celiac Plexus (Plexus Cœliacus; Solar Plexus) - The celiac plexus, the largest of the three sympathetic plexuses, is
situated at the level of the upper part of the first lumbar vertebra and is composed of two large ganglia, the celiac ganglia,
and a dense net-work of nerve fibers uniting them together. It surrounds the celiac artery and the root of the superior mesenteric artery. It lies behind the stomach and the omental bursa, in front of the crura of the diaphragm and the commencement of the abdominal aorta, and between the suprarenal glands. The plexus and the ganglia receive the greater and lesser
splanchnic nerves of both sides and some filaments from the right vagus, and give off numerous secondary plexuses along
the neighboring arteries.
The Celiac Ganglia (ganglia caeliaca; semilunar ganglia) are two large irregularlyshaped masses having the appearance of
lymph glands and placed one on either side of the middle line in front of the crura of the diaphragm close to the suprarenal
glands, that on the right side being placed behind the inferior vena cava. The upper part of each ganglion is joined by the
greater splanchnic nerve, while the lower part, which is segmented off and named the aorticorenal ganglion, receives the
lesser splanchnic nerve and gives off the greater part of the renal plexus.
The secondary plexuses springing from or connected with the celiac plexus are the
Phrenic.
Renal. Hepatic.
Spermatic.
Lienal. Superior mesenteric.
Superior gastric.
Abdominal aortic.
Suprarenal.
Inferior mesenteric.
The phrenic plexus (plexus phrenicus) accompanies the inferior phrenic artery to the diaphragm, some filaments passing
to the suprarenal gland. It arises from the upper part of the celiac ganglion, and is larger on the right than on the left side. It
receives one or two branches from the phrenic nerve. At the point of junction of the right phrenic plexus with the phrenic
nerve is a small ganglion (ganglion phrenicum). This plexus distributes branches to the inferior vena cava, and to the suprarenal and hepatic plexuses.
The hepatic plexus (plexus hepaticus), the largest offset from the celiac plexus, receives filaments from the left vagus and
right phrenic nerves. It accompanies the hepatic artery, ramifying upon its branches, and upon those of the portal vein in the
substance of the liver. Branches from this plexus accompany all the divisions of the hepatic artery. A considerable plexus
accompanies the gastroduodenal artery and is continued as the inferior gastric plexus on the right gastroepiploic artery
along the greater curvature of the stomach, where it unites with offshoots from the lienal plexus.
The lienal plexus (plexus lienalis; splenic plexus) is formed by branches from the celiac plexus, the left celiac ganglion,
and from the right vagus nerve. It accompanies the lienal artery to the spleen, giving off, in its course, subsidiary plexuses
along the various branches of the artery.
The superior gastric plexus (plexus gastricus superior; gastric or coronary plexus) accompanies the left gastric artery along
the lesser curvature of the stomach, and joins with branches from the left vagus.
The suprarenal plexus (plexus suprarenalis) is formed by branches from the celiac plexus, from the celiac ganglion, and
from the phrenic and greater splanchnic nerves, a ganglion being formed at the point of junction with the latter nerve. The
plexus supplies the suprarenal gland, being distributed chiefly to its medullary portion; its branches are remarkable for their
large size in comparison with that of the organ they supply.
The renal plexus (plexus renalis) is formed by filaments from the celiac plexus, the aorticorenal ganglion, and the aortic
plexus. It is joined also by the smallest splanchnic nerve. The nerves from these sources, fifteen or twenty in number, have
a few ganglia developed upon them. They accompany the branches of the renal artery into the kidney; some filaments are
distributed to the spermatic plexus and, on the right side, to the inferior vena cava.
The spermatic plexus (plexus spermaticus) is derived from the renal plexus, receiving branches from the aortic plexus. It
accompanies the internal spermatic artery to the testis. In the female, the ovarian plexus (plexus arteriae ovaricae) arises
from the renal plexus, and is distributed to the ovary, and fundus of the uterus.
The superior mesenteric plexus (plexus mesentericus superior) is a continuation of the lower part of the celiac plexus, receiving a branch from the junction of the right vagus nerve with the plexus. It surrounds the superior mesenteric artery,
accompanies it into the mesentery, and divides into a number of secondary plexuses, which are distributed to all the parts
supplied by the artery, viz., pancreatic branches to the pancreas; intestinal branches to the small intestine; and ileocolic,
right colic, and middle colic branches, which supply the corresponding parts of the great intestine. The nerves composing
this plexus are white in color and firm in texture; in the upper part of the plexus close to the origin of the superior mesenteric artery is a ganglion (ganglion mesentericum superius).
The abdominal aortic plexus (plexus aorticus abdominalis; aortic plexus) is formed by branches derived, on either side,
from the celiac plexus and ganglia, and receives filaments from some of the lumbar ganglia. It is situated upon the sides
and front of the aorta, between the origins of the superior and inferior mesenteric arteries. From this plexus arise part of the
spermatic, the inferior mesenteric, and the hypogastric plexuses; it also distributes filaments to the inferior vena cava.
The inferior mesenteric plexus (plexus mesentericus inferior) is derived chiefly from the aortic plexus. It surrounds the
inferior mesenteric artery, and divides into a number of secondary plexuses, which are distributed to all the parts supplied
by the artery, viz., the left colic and sigmoid plexuses, which supply the descending and sigmoid parts of the colon; and the
superior hemorrhoidal plexus, which supplies the rectum and joins in the pelvis with branches from the pelvic plexuses.
The Hypogastric Plexus (Plexus Hypogastricus) - The hypogastric plexus is situated in front of the last lumbar vertebra and
the promontory of the sacrum, between the two common iliac arteries, and is formed by the union of numerous filaments,
which descend on either side from the aortic plexus, and from the lumbar ganglia; it divides, below, into two lateral portions which are named the pelvic plexuses.
The Pelvic Plexuses - The pelvic plexuses supply the viscera of the pelvic cavity, and are situated at the sides of the rectum
in the male, and at the sides of the rectum and vagina in the female. They are formed on either side by a continuation of the
hypogastric plexus, by the sacral sympathetic efferent fibers from the second, third, and fourth sacral nerves, and by a few
filaments from the first two sacral ganglia. At the points of junction of these nerves small ganglia are found. From these
plexuses numerous branches are distributed to the viscera of the pelvis. They accompany the branches of the hypogastric
artery.
The Middle Hemorrhoidal Plexus (plexus haemorrhoidalis medius) arises from the upper part of the pelvic plexus. It supplies the rectum, and joins with branches of the superior hemorrhoidal plexus.
The Vesical Plexus (plexus vesicalis) arises from the forepart of the pelvic plexus. The nerves composing it are numerous,
and contain a large proportion of spinal nerve fibers. They accompany the vesicle arteries, and are distributed to the sides
and fundus of the bladder. Numerous filaments also pass to the vesiculae seminales and ductus deferentes; those accompanying the ductus deferens join, on the spermatic cord, with branches from the spermatic plexus.
The Prostatic Plexus (plexus prostaticus) is continued from the lower part of the pelvic plexus. The nerves composing it
are of large size. They are distributed to the prostate vesiculae seminales and the corpora cavernosa of the penis and urethra. The nerves supplying the corpora cavernosa consist of two sets, the lesser and greater cavernous nerves, which arise
from the forepart of the prostatic plexus, and, after joining with branches from the pudendal nerve, pass forward beneath
the public arch.
The lesser cavernous nerves (nn. cavernosi penis minores; small cavernous nerves) perforate the fibrous covering of the
penis, near its root.
The greater cavernous nerve (n. cavernosus penis major; large cavernous plexus) passes forward along the dorsum of the
penis, joins with the dorsal nerve of the penis, and is distributed to the corpora cavernosa.
The Vaginal Plexus arises from the lower part of the pelvic plexus. It is distributed to the walls of the vagina, to the erectile tissue of the vestibule, and to the clitoris. The nerves composing this plexus contain, like the vesical, a large proportion
of spinal nerve fibers.
The Uterine Plexus accompanies the uterine artery to the side of the uterus, between the layers of the broad ligament; it
communicates with the ovarian plexus.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 26. Circles of blood circulation. Anatomy of heart: structure of chambers and
walls.
The aim: to learn the general anatomy of circulatory system, structure and relations of the heart.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The vascular system is divided for descriptive purposes into (a) the blood vascular system, which comprises the heart and
bloodvessels for the circulation of the blood; and (b) the lymph vascular system, consisting of lymph glands and lymphatic
vessels, through which a colorless fluid, the lymph, circulates. It must be noted, however, that the two systems communicate with each other and are intimately associated developmentally.
The heart is the central organ of the blood vascular system, and consists of a hollow muscle; by its contraction the blood is
pumped to all parts of the body through a complicated series of tubes, termed arteries. The arteries undergo enormous ramification in their course throughout the body, and end in minute vessels, called arterioles, which in their turn open into a
close-meshed network of microscopic vessels, termed capillaries. After the blood has passed through the capillaries it is
collected into a series of larger vessels, called veins, by which it is returned to the heart. The passage of the blood through
the heart and blood-vessels constitutes what is termed the circulation of the blood, of which the following is an outline.
The human heart is divided by septa into right and left halves, and each half is further divided into two cavities, an upper
termed the atrium and a lower the ventricle. The heart therefore consists of four chambers, two, the right atrium and right
ventricle, forming the right half, and two, the left atrium and left ventricle the left half. The right half of the heart contains
venous or impure blood; the left, arterial or pure blood. The atria are receiving chambers, and the ventricles distributing
ones. From the cavity of the left ventricle the pure blood is carried into a large artery, the aorta, through the numerous
branches of which it is distributed to all parts of the body, with the exception of the lungs. In its passage through the capillaries of the body the blood gives up to the tissues the materials necessary for their growth and nourishment, and at the
same time receives from the tissues the waste products resulting from their metabolism. In doing so it is changed from arterial into venous blood, which is collected by the veins and through them returned to the right atrium of the heart. From this
cavity the impure blood passes into the right ventricle, and is thence conveyed through the pulmonary arteries to the lungs.
In the capillaries of the lungs it again becomes arterialized, and is then carried to the left atrium by the pulmonary veins.
From the left atrium it passes into the left ventricle, from which the cycle once more begins.
The course of the blood from the left ventricle through the body generally to the right side of the heart constitutes the
greater or systemic circulation, while its passage from the right ventricle through the lungs to the left side of the heart is
termed the lesser or pulmonary circulation.
It is necessary, however, to state that the blood which circulates through the spleen, pancreas, stomach, small intestine,
and the greater part of the large intestine is not returned directly from these organs to the heart, but is conveyed by the portal vein to the liver. In the liver this vein divides, like an artery, and ultimately ends in capillary-like vessels (sinusoids),
from which the rootlets of a series of veins, called the hepatic veins, arise; these carry the blood into the inferior vena cava,
whence it is conveyed to the right atrium. From this it will be seen that the blood contained in the portal vein passes
through two sets of vessels: (1) the capillaries in the spleen, pancreas, stomach, etc., and (2) the sinusoids in the liver. The
blood in the portal vein carries certain of the products of digestion: the carbohydrates, which are mostly taken up by the
liver cells and stored as glycogen, and the protein products which remain in solution and are carried into the general circulation to the various tissues and organs of the body.
Speaking generally, the arteries may be said to contain pure and the veins impure blood. This is true of the systemic, but
not of the pulmonary vessels, since it has been seen that the impure blood is conveyed from the heart to the lungs by the
pulmonary arteries, and the pure blood returned from the lungs to the heart by the pulmonary veins. Arteries, therefore,
must be defined as vessels which convey blood from the heart, and veins as vessels which return blood to the heart.
The pericardium is a conical fibro-serous sac, in which the heart and the roots of the great vessels are contained. It is placed
behind the sternum and the cartilages of the third, fourth, fifth, sixth, and seventh ribs of the left side, in the mediastinal
cavity.
In front, it is separated from the anterior wall of the thorax, in the greater part of its extent, by the lungs and pleurae; but a
small area, somewhat variable in size, and usually corresponding with the left half of the lower portion of the body of the
sternum and the medial ends of the cartilages of the fourth and fifth ribs of the left side, comes into direct relationship with
the chest wall. The lower extremity of the thymus, in the child, is in contact with the front of the upper part of the pericardium. Behind, it rests upon the bronchi, the esophagus, the descending thoracic aorta, and the posterior part of the mediastinal surface of each lung. Laterally, it is covered by the pleurae, and is in relation with the mediastinal surfaces of the
lungs; the phrenic nerve, with its accompanying vessels, descends between the pericardium and pleura on either side.
The heart is a hollow muscular organ of a somewhat conical form; it lies between the lungs in the middle mediastinum and
is enclosed in the pericardium. It is placed obliquely in the chest behind the body of the sternum and adjoining parts of the
rib cartilages, and projects farther into the left than into the right half of the thoracic cavity, so that about one-third of it is
situated on the right and two-thirds on the left of the median plane.
Size. - The heart, in the adult, measures about 12 cm. in length, 8 to 9 cm. in breadth at the broadest part, and 6 cm. in
thickness. Its weight, in the male, varies from 280 to 340 grams; in the female, from 230 to 280 grams. The heart continues
to increase in weight and size up to an advanced period of life; this increase is more marked in men than in women.
Component Parts. - As has already been stated, the heart is subdivided by septa into right and left halves, and a constriction
subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The
heart therefore consists of four chambers, viz., right and left atria, and right and left ventricles.
The division of the heart into four cavities is indicated on its surface by grooves. The atria are separated from the ventricles by the coronary sulcus (auriculoventricular groove); this contains the trunks of the nutrient vessels of the heart, and is
deficient in front, where it is crossed by the root of the pulmonary artery. The interatrial groove, separating the two atria, is
scarcely marked on the posterior surface, while anteriorly it is hidden by the pulmonary artery and aorta. The ventricles are
separated by two grooves, one of which, the anterior longitudinal sulcus, is situated on the sternocostal surface of the heart,
close to its left margin, the other posterior longitudinal sulcus, on the diaphragmatic surface near the right margin; these
grooves extend from the base of the ventricular portion to a notch, the incisura apicis cordis, on the acute margin of the
heart just to the right of the apex.
The base (basis cordis), directed upward, backward, and to the right, is separated from the fifth, sixth, seventh, and eighth
thoracic vertebrae by the esophagus, aorta, and thoracic duct. It is formed mainly by the left atrium, and, to a small extent,
by the back part of the right atrium. Somewhat quadrilateral in form, it is in relation above with the bifurcation of the pulmonary artery, and is bounded below by the posterior part of the coronary sulcus, containing the coronary sinus. On the
right it is limited by the sulcus terminalis of the right atrium, and on the left by the ligament of the left vena cava and the
oblique vein of the left atrium. The four pulmonary veins, two on either side, open into the left atrium, while the superior
vena cava opens into the upper, and the anterior vena cava into the lower, part of the right atrium.
The Apex (apex cordis). - The apex is directed downward, forward, and to the left, and is overlapped by the left lung and
pleura: it lies behind the fifth left intercostal space, 8 to 9 cm. from the mid-sternal line, or about 4 cm. below and 2 mm. to
the medial side of the left mammary papilla.
The sternocostal surface is directed forward, upward, and to the left. Its lower part is convex, formed chiefly by the right
ventricle, and traversed near its left margin by the anterior longitudinal sulcus. Its upper part is separated from the lower by
the coronary sulcus, and is formed by the atria; it presents a deep concavity, occupied by the ascending aorta and the pulmonary artery.
The diaphragmatic surface, directed downward and slightly backward, is formed by the ventricles, and rests upon the central tendon and a small part of the left muscular portion of the diaphragm. It is separated from the base by the posterior part
of the coronary sulcus, and is traversed obliquely by the posterior longitudinal sulcus.
The right margin of the heart is long, and is formed by the right atrium above and the right ventricle below. The atrial portion is rounded and almost vertical; it is situated behind the third, fourth, and fifth right costal cartilages about 1.25 cm.
from the margin of the sternum. The ventricular portion, thin and sharp, is named the acute margin; it is nearly horizontal,
and extends from the sternal end of the sixth right costal cartilage to the apex of the heart.
The left or obtuse margin is shorter, full, and rounded: it is formed mainly by the left ventricle, but to a slight extent,
above, by the left atrium. It extends from a point in the second left intercostal space, about 2.5 mm. from the sternal margin,
obliquely downward, with a convexity to the left, to the apex of the heart.
Right Atrium (atrium dextrum; right auricle). - The right atrium is larger than the left, but its walls are somewhat thinner,
measuring about 2 mm.; its cavity is capable of containing about 57 c.c. It consists of two parts: a principal cavity, or sinus
venarum, situated posteriorly, and an anterior, smaller portion, the auricula.
Sinus Venarum (sinus venosus). - The sinus venarum is the large quadrangular cavity placed between the two venae cavae.
Its walls, which are extremely thin, are connected below with the right ventricle, and medially with the left atrium, but are
free in the rest of their extent.
Auricula (auricula dextra; right auricular appendix). - The auricula is a small conical muscular pouch, the margins of which
present a dentated edge. It projects from the upper and front part of the sinus forward and toward the left side, overlapping
the root of the aorta.
The separation of the auricula from the sinus venarum is indicated externally by a groove, the terminal sulcus, which extends from the front of the superior vena cava to the front of the inferior vena cava, and represents the line of union of the
sinus venosus of the embryo with the primitive atrium. On the inner wall of the atrium the separation is marked by a vertical, smooth, muscular ridge, the terminal crest. Behind the crest the internal surface of the atrium is smooth, while in front
of it the muscular fibers of the wall are raised into parallel ridges resembling the teeth of a comb, and hence named the
musculi pectinati.
Its interior presents the following parts for examination:
Superior vena cava
Valve of the inferior vena cava.
Inferior vena cava.
Openings » Coronary sinus
Valves »
Foramina venarum minimarum.
Valve of the coronary sinus.
Atrioventricular.
Fossa ovalis
Limbus fossae ovalis
Intervenous tubercle.
Musculi pectinati
Crista terminalis
The superior vena cava returns the blood from the upper half of the body, and opens into the upper and back part of the
atrium, the direction of its orifice being downward and forward. Its opening has no valve.
The inferior vena cava, larger than the superior, returns the blood from the lower half of the body, and opens into the lowest part of the atrium, near the atrial septum, its orifice being directed upward and backward, and guarded by a rudimentary
valve, the valve of the inferior vena cava (Eustachian valve). The blood entering the atrium through the superior vena cava
is directed downward and forward, i.e., toward the atrioventricular orifice, while that entering through the inferior vena
cava is directed upward and backward, toward the atrial septum. This is the normal direction of the two currents in fetal
life.
The coronary sinus opens into the atrium, between the orifice of the inferior vena cava and the atrioventricular opening. It
returns blood from the substance of the heart and is protected by a semicircular valve, the valve of the coronary sinus (valve
of Thebesius).
The foramina venarum minimarum (foramina Thebesii) are the orifices of minute veins (venœ cordis minimœ), which
return blood directly from the muscular substance of the heart.
The atrioventricular opening (tricuspid orifice) is the large oval aperture of communication between the atrium and the
ventricle; it will be described with the right ventricle.
The valve of the inferior vena cava (valvula venœ cavœ inferioris [Eustachii]; Eustachian valve) is situated in front of the
orifice of the inferior vena cava. It is semilunar in form, its convex margin being attached to the anterior margin of the orifice; its concave margin, which is free, ends in two cornua, of which the left is continuous with the anterior edge of the limbus fossae ovalis while the right is lost on the wall of the atrium. The valve is formed by a duplicature of the lining membrane of the atrium, containing a few muscular fibers. In the fetus this valve is of large size, and serves to direct the blood
from the inferior vena cava, through the foramen ovale, into the left atrium. In the adult it occasionally persists, and may
assist in preventing the reflux of blood into the inferior vena cava; more commonly it is small, and may present a cribriform
or filamentous appearance; sometimes it is altogether wanting.
The valve of the coronary sinus (valvula sinus coronarii [Thebesii]; Thebesian valve) is a semicircular fold of the lining
membrane of the atrium, at the orifice of the coronary sinus. It prevents the regurgitation of blood into the sinus during the
contraction of the atrium. This valve may be double or it may be cribriform.
The fossa ovalis is an oval depression on the septal wall of the atrium, and corresponds to the situation of the foramen
ovale in the fetus. It is situated at the lower part of the septum, above and to the left of the orifice of the inferior vena cava.
The limbus fossae ovalis (annulus ovalis) is the prominent oval margin of the fossa ovalis. It is most distinct above and at
the sides of the fossa; below, it is deficient. A small slit-like valvular opening is occasionally found, at the upper margin of
the fossa, leading upward beneath the limbus, into the left atrium; it is the remains of the fetal aperture between the two
atria.
The intervenous tubercle (tuberculum intervenosum; tubercle of Lower) is a small projection on the posterior wall of the
atrium, above the fossa ovalis. It is distinct in the hearts of quadrupeds, but in man is scarcely visible. It was supposed by
Lower to direct the blood from the superior vena cava toward the atrioventricular opening.
Right Ventricle (ventriculus dexter). - The right ventricle is triangular in form, and extends from the right atrium to near the
apex of the heart. Its anterosuperior surface is rounded and convex, and forms the larger part of the sternocostal surface of
the heart. Its under surface is flattened, rests upon the diaphragm, and forms a small part of the diaphragmatic surface of the
heart. Its posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. Its upper and left angle forms a conical pouch, the conus arteriosus, from
which the pulmonary artery arises. A tendinous band, which may be named the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta. The
wall of the right ventricle is thinner than that of the left, the proportion between them being as 1 to 3; it is thickest at the
base, and gradually becomes thinner toward the apex. The cavity equals in size that of the left ventricle, and is capable of
containing about 85 c.c.
Its interior presents the following parts for examination:
Right atrioventricular.
Tricuspid.
Openings »
Valves »
Pulmonary artery
Pulmonary.
Trabeculae carneae
Chordae tendineae
The right atrioventricular orifice is the large oval aperture of communication between the right atrium and ventricle. Situated at the base of the ventricle, it measures about 4 cm. in diameter and is surrounded by a fibrous ring, covered by the
lining membrane of the heart; it is considerably larger than the corresponding aperture on the left side, being sufficient to
admit the ends of four fingers. It is guarded by the tricuspid valve.
The opening of the pulmonary artery is circular in form, and situated at the summit of the conus arteriosus, close to the
ventricular septum. It is placed above and to the left of the atrioventricular opening, and is guarded by the pulmonary semilunar valves.
The tricuspid valve (valvula tricuspidalis) consists of three somewhat triangular cusps or segments. The largest cusp is
interposed between the atrioventricular orifice and the conus arteriosus and is termed the anterior or infundibular cusp. A
second, the posterior or marginal cusp, is in relation to the right margin of the ventricle, and a third, the medial or septal
cusp, to the ventricular septum. They are formed by duplicatures of the lining membrane of the heart, strengthened by intervening layers of fibrous tissue: their central parts are thick and strong, their marginal portions thin and translucent, and in
the angles between the latter small intermediate segments are sometimes seen. Their bases are attached to a fibrous ring
surrounding the atrioventricular orifice and are also joined to each other so as to form a continuous annular membrane,
while their apices project into the ventricular cavity. Their atrial surfaces, directed toward the blood current from the atrium, are smooth; their ventricular surfaces, directed toward the wall of the ventricle, are rough and irregular, and, together
with the apices and margins of the cusps, give attachment to a number of delicate tendinous cords, the chordae tendineae.
The trabeculae carneae (columnœ carneœ) are rounded or irregular muscular columns which project from the whole of the
inner surface of the ventricle, with the exception of the conus arteriosus. They are of three kinds: some are attached along
their entire length on one side and merely form prominent ridges, others are fixed at their extremities but free in the middle,
while a third set (musculi papillares) are continuous by their bases with the wall of the ventricle, while their apices give
origin to the chordae tendineae which pass to be attached to the segments of the tricuspid valve. There are two papillary
muscles, anterior and posterior: of these, the anterior is the larger, and its chordae tendineae are connected with the anterior
and posterior cusps of the valve: the posterior papillary muscle sometimes consists of two or three parts; its chordae
tendineae are connected with the posterior and medial cusps. In addition to these, some chordae tendineae spring directly
from the ventricular septum, or from small papillary eminences on it, and pass to the anterior and medial cusps. A muscular
band, well-marked in sheep and some other animals, frequently extends from the base of the anterior papillary muscle to
the ventricular septum. From its attachments it may assist in preventing overdistension of the ventricle, and so has been
named the moderator band.
The pulmonary semilunar valves are three in number, two in front and one behind, formed by duplicatures of the lining
membrane, strengthened by fibrous tissue. They are attached, by their convex margins, to the wall of the artery, at its junction with the ventricle, their free borders being directed upward into the lumen of the vessel. The free and attached margins
of each are strengthened by tendinous fibers, and the former presents, at its middle, a thickened nodule (corpus Arantii).
From this nodule tendinous fibers radiate through the segment to its attached margin, but are absent from two narrow crescentic portions, the lunulae, placed one on either side of the nodule immediately adjoining the free margin. Between the
semilunar valves and the wall of the pulmonary artery are three pouches or sinuses (sinuses of Valsalva).
Left Atrium (atrium sinistum; left auricle). - The left atrium is rather smaller than the right, but its walls are thicker, measuring about 3 mm.; it consists, like the right, of two parts, a principal cavity and an auricula.
The principal cavity is cuboidal in form, and concealed, in front, by the pulmonary artery and aorta; in front and to the
right it is separated from the right atrium by the atrial septum; opening into it on either side are the two pulmonary veins.
Auricula (auricula sinistra; left auricular appendix). - The auricula is somewhat constricted at its junction with the principal
cavity; it is longer, narrower, and more curved than that of the right side, and its margins are more deeply indented. It is
directed forward and toward the right and overlaps the root of the pulmonary artery.
The interior of the left atrium presents the following parts for examination:
Openings of the four pulmonary veins.
Left atrioventricular opening.
Musculi pectinati.
The pulmonary veins, four in number, open into the upper part of the posterior surface of the left atrium - two on either
side of its middle line: they are not provided with valves. The two left veins frequently end by a common opening.
The left atrioventricular opening is the aperture between the left atrium and ventricle, and is rather smaller than the corresponding opening on the right side.
The musculi pectinati, fewer and smaller than in the right auricula, are confined to the inner surface of the auricula. On
the atrial septum may be seen a lunated impression, bounded below by a crescentic ridge, the concavity of which is turned
upward. The depression is just above the fossa ovalis of the right atrium.
Left Ventricle (ventriculus sinister). - The left ventricle is longer and more conical in shape than the right, and on transverse
section its concavity presents an oval or nearly circular outline. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart. Its walls are about three times as
thick as those of the right ventricle.
Its interior presents the following parts for examination:
Left atrioventricular.
Bicuspid or Mitral.
Valves »
Aortic.
Aortic.
Trabeculae carneae.
Chordae tendineae
The left atrioventricular opening (mitral orifice) is placed below and to the left of the aortic orifice. It is a little smaller
than the corresponding aperture of the opposite side, admitting only two fingers. It is surrounded by a dense fibrous ring,
covered by the lining membrane of the heart, and is guarded by the bicuspid or mitral valve.
The aortic opening is a circular aperture, in front and to the right of the atrioventricular, from which it is separated by the
anterior cusp of the bicuspid valve. Its orifice is guarded by the aortic semilunar valves. The portion of the ventricle immediately below the aortic orifice is termed the aortic vestibule, and possesses fibrous instead of muscular walls.
The bicuspid or mitral valve (valvula bicuspidalis [metralis]) is attached to the circumference of the left atrioventricular
orifice in the same way that the tricuspid valve is on the opposite side. It consists of two triangular cusps, formed by duplicatures of the lining membrane, strengthened by fibrous tissue, and containing a few muscular fibers. The cusps are of unequal size, and are larger, thicker, and stronger than those of the tricuspid valve. The larger cusp is placed in front and to the
right between the atrioventricular and aortic orifices, and is known as the anterior or aortic cusp; the smaller or posterior
cusp is placed behind and to the left of the opening. Two smaller cusps are usually found at the angles of junction of the
larger. The cusps of the bicuspid valve are furnished with chordae tendineae, which are attached in a manner similar to
those on the right side; they are, however, thicker, stronger, and less numerous.
The aortic semilunar valves are three in number, and surround the orifice of the aorta; two are anterior (right and left) and
one posterior. They are similar in structure, and in their mode of attachment, to the pulmonary semilunar valves, but are
larger, thicker, and stronger; the lunulae are more distinct, and the noduli or corpora Arantii thicker and more prominent.
Opposite the valves the aorta presents slight dilatations, the aortic sinuses (sinuses of Valsalva), which are larger than those
at the origin of the pulmonary artery.
The trabeculae carneae are of three kinds, like those upon the right side, but they are more numerous, and present a dense
interlacement, especially at the apex, and upon the posterior wall of the ventricle. The musculi papillares are two in number, one being connected to the anterior, the other to the posterior wall; they are of large size, and end in rounded extremities from which the chordae tendineae arise. The chordae tendineae from each papillary muscle are connected to both cusps
of the bicuspid valve.
Ventricular Septum (septum ventriculorum; interventricular septum). - The ventricular septum is directed obliquely backward and to the right, and is curved with the convexity toward the right ventricle: its margins correspond with the anterior
and posterior longitudinal sulci. The greater portion of it is thick and muscular and constitutes the muscular ventricular septum, but its upper and posterior part, which separates the aortic vestibule from the lower part of the right atrium and upper
part of the right ventricle, is thin and fibrous, and is termed the membranous ventricular septum. An abnormal communication may exist between the ventricles at this part owing to defective development of the membranous septum.
Strucutre. - The heart consists of muscular fibers, and of fibrous rings which serve for their attachment. It is covered by the
visceral layer of the serous pericardium (epicardium), and lined by the endocardium. Between these two membranes is the
muscular wall or myocardium.
The endocardium is a thin, smooth membrane which lines and gives the glistening appearance to the inner surface of the
heart; it assists in forming the valves by its reduplications, and is continuous with the lining membrane of the large
bloodvessels. It consists of connective tissue and elastic fibers, and is attached to the muscular structure by loose elastic
tissue which contains bloodvessels and nerves; its free surface is covered by endothelial cells.
The fibrous rings surround the atrioventricular and arterial orifices, and are stronger upon the left than on the right side of
the heart. The atrioventricular rings serve for the attachment of the muscular fibers of the atria and ventricles, and for the
attachment of the bicuspid and tricuspid valves. The left atrioventricular ring is closely connected, by its right margin, with
the aortic arterial ring; between these and the right atrioventricular ring is a triangular mass of fibrous tissue, the trigonum
Openings »
fibrosum, which represents the os cordis seen in the heart of some of the larger animals, as the ox and elephant. Lastly,
there is the tendinous band, already referred to, the posterior surface of the conus arteriosus.
The fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves. Each
ring receives, by its ventricular margin, the attachment of some of the muscular fibers of the ventricles; its opposite margin
presents three deep semicircular notches, to which the middle coat of the artery is firmly fixed. The attachment of the artery
to its fibrous ring is strengthened by the external coat and serous membrane externally, and by the endocardium internally.
From the margins of the semicircular notches the fibrous structure of the ring is continued into the segments of the valves.
The middle coat of the artery in this situation is thin, and the vessel is dilated to form the sinuses of the aorta and pulmonary artery.
Cardiac Muscular Tissue. - The fibers of the heart differ very remarkably from those of other striped muscles. They are
smaller by one-third, and their transverse striae are by no means so well-marked. They show faint longitudinal striation.
The fibers are made up of distinct quadrangular cells, joined end to end so as to form a syncytium. Each cell contains a
clear oval nucleus, situated near its center. The extremities of the cells have a tendency to branch or divide, the subdivisions
uniting with offsets from other cells, and thus producing an anastomosis of the fibers. The connective tissue between the
bundles of fibers is much less than in ordinary striped muscle, and no sarcolemma has been proved to exist.
Purkinje Fibers. - Between the endocardium and the ordinary cardiac muscle are found, imbedded in a small amount of
connective tissue, peculiar fibers known as Purkinje fibers. They are found in certain mammals and in birds, and can be
best seen in the sheep’s heart, where they form a considerable portion of the moderator band and also appear as gelatinouslooking strands on the inner walls of the atria and ventricles. They also occur in the human heart associated with the terminal distributions of the bundle of His. The fibers are very much larger in size than the cardiac cells and differ from them in
several ways. In longitudinal section they are quadrilateral in shape, being about twice as long as they are broad. The central portion of each fiber contains one or more nuclei and is made up of granular protoplasm, with no indication of striations, while the peripheral portion is clear and has distinct transverse striations. The fibers are intimately connected with
each other, possess no definite sarcolemma, and do not branch.
The muscular structure of the heart consists of bands of fibers, which present an exceedingly intricate interlacement. They
comprise (a) the fibers of the atria, (b) the fibers of the ventricles, and (c) the atrioventricular bundle of His.
The fibers of the atria are arranged in two layers - a superficial, common to both cavities, and a deep, proper to each. The
superficial fibers are most distinct on the front of the atria, across the bases of which they run in a transverse direction,
forming a thin and incomplete layer. Some of these fibers run into the atrial septum. The deep fibers consist of looped and
annular fibers. The looped fibers pass upward over each atrium, being attached by their two extremities to the corresponding atrioventricular ring, in front and behind. The annular fibers surround the auriculae, and form annular bands around the
terminations of the veins and around the fossa ovalis.
The fibers of the ventricles are arranged in a complex manner, and various accounts have been given of their course and
connections; the following description is based on the work of McCallum. They consist of superficial and deep layers, all
of which, with the exception of two, are inserted into the papillary muscles of the ventricles. The superficial layers consist
of the following: (a) Fibers which spring from the tendon of the conus arteriosus and sweep downward and toward the left
across the anterior longitudinal sulcus and around the apex of the heart, where they pass upward and inward to terminate in
the papillary muscles of the left ventricle; those arising from the upper half of the tendon of the conus arteriosus pass to the
anterior papillary muscle, those from the lower half to the posterior papillary muscle and the papillary muscles of the septum. (b) Fibers which arise from the right atrioventricular ring and run diagonally across the diaphragmatic surface of the
right ventricle and around its right border on to its costosternal surface, where they dip beneath the fibers just described,
and, crossing the anterior longitudinal sulcus, wind around the apex of the heart and end in the posterior papillary muscle of
the left ventricle. (c) Fibers which spring from the left atrioventricular ring, and, crossing the posterior longitudinal sulcus,
pass successively into the right ventricle and end in its papillary muscles. The deep layers are three in number; they arise in
the papillary muscles of one ventricle and, curving in an S-shaped manner, turn in at the longitudinal sulcus and end in the
papillary muscles of the other ventricle. The layer which is most superficial in the right ventricle lies next the lumen of the
left, and vice versa. Those of the first layer almost encircle the right ventricle and, crossing in the septum to the left, unite
with the superficial fibers from the right atrioventricular ring to form the posterior papillary muscle. Those of the second
layer have a less extensive course in the wall of the right ventricle, and a correspondingly greater course in the left, where
they join with the superficial fibers from the anterior half of the tendon of the conus arteriosus to form the papillary muscles of the septum. Those of the third layer pass almost entirely around the left ventricle and unite with the superficial fibers
from the lower half of the tendon of the conus arteriosus to form the anterior papillary muscle. Besides the layers just described there are two bands which do not end in papillary muscles. One springs from the right atrioventricular ring and
crosses in the atrioventricular septum; it then encircles the deep layers of the left ventricle and ends in the left atrioventricular ring. The second band is apparently confined to the left ventricle; it is attached to the left atrioventricular ring, and encircles the portion of the ventricle adjacent to the aortic orifice.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 27. Conducting system of heart. Vessels and nerves of heart. Relations of heart.
Pericardium.
The aim: to learn the structure of the heart conduction system, innervation and blood supplement of heart
proper, the anatomy and relations of pericardium.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The atrioventricular bundle of His is the only direct muscular connection known to exist between the atria and the ventricles. Its cells differ from ordinary cardiac muscle cells in being more spindle-shaped. They are, moreover, more loosely
arranged and have a richer vascular supply than the rest of the heart muscle. It arises in connection with two small collections of spindle-shaped cells, the sinoatrial and atrioventricular nodes. The sinoatrial node is situated on the anterior border
of the opening of the superior vena cava; from its strands of fusiform fibers run under the endocardium of the wall of the
atrium to the atrioventricular node. The atrioventricular node lies near the orifice of the coronary sinus in the annular and
septal fibers of the right atrium; from it the atrioventricular bundle passes forward in the lower part of the membranous septum, and divides into right and left fasciculi. These run down in the right and left ventricles, one on either side of the ventricular septum, covered by endocardium. In the lower parts of the ventricles they break up into numerous strands which
end in the papillary muscles and in the ventricular muscle generally. The greater portion of the atrioventricular bundle consists of narrow, somewhat fusiform fibers, but its terminal strands are composed of Purkinje fibers.
Dr. A. Morison has shown that in the sheep and pig the atrioventricular bundle “is a great avenue for the transmission of
nerves from the auricular to the ventricular heart; large and numerous nerve trunks entering the bundle and coursing with
it.” From these, branches pass off and form plexuses around groups of Purkinje cells, and from these plexuses fine fibrils
go to innervate individual cells.
Clinical and experimental evidence go to prove that this bundle conveys the impulse to systolic contraction from the atrial
septum to the ventricles.
Vessels and Nerves. - The arteries supplying the heart are the right and left coronary from the aorta; the veins end in the
right atrium.
The lymphatics end in the thoracic and right lymphatic ducts.
The nerves are derived from the cardiac plexus, which are formed partly from the vagi, and partly from the sympathetic
trunks. They are freely distributed both on the surface and in the substance of the heart, the separate nerve filaments being
furnished with small ganglia.
The Cardiac Cycle and the Actions of the Valves. - By the contractions of the heart the blood is pumped through the arteries
to all parts of the body. These contractions occur regularly and at the rate of about seventy per minute. Each wave of contraction or period of activity is followed by a period of rest, the two periods constituting what is known as a cardiac cycle.
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Each cardiac cycle consists of three phases, which succeed each other as follows: (1) a short simultaneous contraction of
both atria, termed the atrial systole, followed, lowed, after a slight pause, by (2) a simultaneous, but more prolonged, contraction of both ventricles, named the ventricular systole, and (3) a period of rest, during which the whole heart is relaxed.
The atrial contraction commences around the venous openings, and sweeping over the atria forces their contents through
the atrioventricular openings into the ventricles, regurgitation into the veins being prevented by the contraction of their
muscular coats. When the ventricles contract, the tricuspid and bicuspid valves are closed, and prevent the passage of the
blood back into the atria; the musculi papillares at the same time are shortened, and, pulling on the chordae tendineae, prevent the inversion of the valves into the atria. As soon as the pressure in the ventricles exceeds that in the pulmonary artery
and aorta, the valves guarding the orifices of these vessels are opened and the blood is driven from the right ventricle into
the pulmonary artery and from the left into the aorta. The moment the systole of the ventricles ceases, the pressure of the
blood in the pulmonary artery and aorta closes the pulmonary and aortic semilunar valves to prevent regurgitation of blood
into the ventricles, the valves remaining shut until reopened by the next ventricular systole. During the period of rest the
tension of the tricuspid and bicuspid valves is relaxed, and blood is flowing from the veins into the atria, being aspirated by
negative intrathoracic pressure, and slightly also from the atria into the ventricles. The average duration of a cardiac cycle
is about 8/10 of a second, made up as follows:
Atrial systole, 1/10.
Atrial diastole, 7/10.
Ventricular systole, 3/10. Ventricular diastole, 5/10.
Total systole, 4/10.
Complete diastole, 4/10.
The rhythmical action of the heart is muscular in origin - that is to say, the heart muscle itself possesses the inherent property of contraction apart from any nervous stimulation. The more embryonic the muscle the better is it able to initiate and
propagate the contraction wave; this explains why the normal systole of the heart starts at the entrance of the veins, for
there the muscle is most embryonic in nature. At the atrioventricular junction there is a slight pause in the wave of muscular
contraction. To obviate this so far as possible a peculiar band of marked embryonic type passes across the junction and so
carries on the contraction wave to the ventricles. This band, composed of special fibers, is the atrioventricular bundle of
His. The nerves, although not concerned in originating the contractions of the heart muscle, play an important role in regulating their force and frequency in order to subserve the physiological needs of the organism.
The pericardium is a conical fibro-serous sac, in which the heart and the roots of the great vessels are contained. It is placed
behind the sternum and the cartilages of the third, fourth, fifth, sixth, and seventh ribs of the left side, in the mediastinal
cavity.
In front, it is separated from the anterior wall of the thorax, in the greater part of its extent, by the lungs and pleurae; but a
small area, somewhat variable in size, and usually corresponding with the left half of the lower portion of the body of the
sternum and the medial ends of the cartilages of the fourth and fifth ribs of the left side, comes into direct relationship with
the chest wall. The lower extremity of the thymus, in the child, is in contact with the front of the upper part of the pericardium. Behind, it rests upon the bronchi, the esophagus, the descending thoracic aorta, and the posterior part of the mediastinal surface of each lung. Laterally, it is covered by the pleurae, and is in relation with the mediastinal surfaces of the
lungs; the phrenic nerve, with its accompanying vessels, descends between the pericardium and pleura on either side.
Structure of the Pericardium. - Although the pericardium is usually described as a single sac, an examination of its structure shows that it consists essentially of two sacs intimately connected with one another, but totally different in structure.
The outer sac, known as the fibrous pericardium, consists of fibrous tissue. The inner sac, or serous pericardium, is a delicate membrane which lies within the fibrous sac and lines its walls; it is composed of a single layer of flattened cells resting
on loose connective tissue. The heart invaginates the wall of the serous sac from above and behind, and practically obliterates its cavity, the space being merely a potential one.
The fibrous pericardium forms a flask-shaped bag, the neck of which is closed by its fusion with the external coats of the
great vessels, while its base is attached to the central tendon and to the muscular fibers of the left side of the diaphragm. In
some of the lower mammals the base is either completely separated from the diaphragm or joined to it by some loose areolar tissue; in man much of its diaphragmatic attachment consists of loose fibrous tissue which can be readily broken down,
but over a small area the central tendon of the diaphragm and the pericardium are completely fused. Above, the fibrous
pericardium not only blends with the external coats of the great vessels, but is continuous with the pretracheal layer of the
deep cervical fascia. By means of these upper and lower connections it is securely anchored within the thoracic cavity. It is
also attached to the posterior surface of the sternum by the superior and inferior sternopericardiac ligaments; the upper
passing to the manubrium, and the lower to the xiphoid process.
The vessels receiving fibrous prolongations from this membrane are: the aorta, the superior vena cava, the right and left
pulmonary arteries, and the four pulmonary veins. The inferior vena cava enters the pericardium through the central tendon
of the diaphragm, and receives no covering from the fibrous layer.
The serous pericardium is, as already stated, a closed sac which lines the fibrous pericardium and is invaginated by the
heart; it therefore consists of a visceral and a parietal portion. The visceral portion, or epicardium, covers the heart and the
great vessels, and from the latter is continuous with the parietal layer which lines the fibrous pericardium. The portion
which covers the vessels is arranged in the form of two tubes. The aorta and pulmonary artery are enclosed in one tube, the
arterial mesocardium. The superior and inferior venae cavae and the four pulmonary veins are enclosed in a second tube,
the venous mesocardium, the attachment of which to the parietal layer presents the shape of an inverted U. The cul-de-sac
enclosed between the limbs of the U lies behind the left atrium and is known as the oblique sinus, while the passage between the venous and arterial mesocardia - i.e., between the aorta and pulmonary artery in front and the atria behind - is
termed the transverse sinus.
The Ligament of the Left Vena Cava. - Between the left pulmonary artery and subjacent pulmonary vein is a triangular fold
of the serous pericardium; it is known as the ligament of the left vena cava (vestigial fold of Marshall). It is formed by the
duplicature of the serous layer over the remnant of the lower part of the left superior vena cava (duct of Cuvier), which becomes obliterated during fetal life, and remains as a fibrous band stretching from the highest left intercostal vein to the left
atrium, where it is continuous with a small vein, the vein of the left atrium (oblique vein of Marshall), which opens into the
coronary sinus.
The arteries of the pericardium are derived from the internal mammary and its musculophrenic branch, and from the descending thoracic aorta.
The nerves of the percardium are derived from the vagus and phrenic nerves, and the sympathetic trunks.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 28. Aorta: parts and relations. Axillary and brachial arteries, their branches.
The aim: to learn the structure and relations of aorta and its main branches.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The aorta is the main trunk of a series of vessels which convey the oxygenated blood to the tissues of the body for their
nutrition. It commences at the upper part of the left ventricle, where it is about 3 cm. in diameter, and after ascending for a
short distance, arches backward and to the left side, over the root of the left lung; it then descends within the thorax on the
left side of the vertebral column, passes into the abdominal cavity through the aortic hiatus in the diaphragm, and ends,
considerably diminished in size (about 1.75 cm. in diameter), opposite the lower border of the fourth lumbar vertebra, by
dividing into the right and left common iliac arteries. Hence it is described in several portions, viz., the ascending aorta, the
arch of the aorta, and the descending aorta, which last is again divided into the thoracic and abdominal aortae.
The Ascending Aorta (Aorta Ascendens). - The ascending aorta is about 5 cm. in length. It commences at the upper part of
the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum;
it passes obliquely upward, forward, and to the right, in the direction of the heart’s axis, as high as the upper border of the
second right costal cartilage, describing a slight curve in its course, and being situated, about 6 cm. behind the posterior
surface of the sternum. At its origin it presents, opposite the segments of the aortic valve, three small dilatations called the
aortic sinuses. At the union of the ascending aorta with the aortic arch the caliber of the vessel is increased, owing to a
bulging of its right wall. This dilatation is termed the bulb of the aorta, and on transverse section presents a somewhat oval
figure. The ascending aorta is contained within the pericardium, and is enclosed in a tube of the serous pericardium, common to it and the pulmonary artery.
Relations. - The ascending aorta is covered at its commencement by the trunk of the pulmonary artery and the right auricula, and, higher up, is separated from the sternum by the pericardium, the right pleura, the anterior margin of the right lung,
some loose areolar tissue, and the remains of the thymus; posteriorly, it rests upon the left atrium and right pulmonary artery. On the right side, it is in relation with the superior vena cava and right atrium, the former lying partly behind it; on the
left side, with the pulmonary artery.
Branches. - The only branches of the ascending aorta are the two coronary arteries which supply the heart; they arise near
the commencement of the aorta immediately above the attached margins of the semilunar valves.
The Coronary Arteries. - The Right Coronary Artery (a. coronaria [cordis] dextra) arises from the right anterior aortic sinus.
It passes at first between the conus arteriosus and the right auricula and then runs in the right portion of the coronary sulcus,
coursing at first from the left to right and then on the diaphragmatic surface of the heart from right to left as far as the posterior longitudinal sulcus, down which it is continued to the apex of the heart as the posterior descending branch. It gives
off a large marginal branch which follows the acute margin of the heart and supplies branches to both surfaces of the right
ventricle. It also gives twigs to the right atrium and to the part of the left ventricle which adjoins the posterior longitudinal
sulcus.
The Left Coronary Artery (a. coronaria [cordis] sinistra), larger than the right, arises from the left anterior aortic sinus and
divides into an anterior descending and a circumflex branch. The anterior descending branch passes at first behind the pulmonary artery and then comes forward between that vessel and the left auricula to reach the anterior longitudinal sulcus,
along which it descends to the incisura apicis cordis; it gives branches to both ventricles. The circumflex branch follows the
left part of the coronary sulcus, running first to the left and then to the right, reaching nearly as far as the posterior longitudinal sulcus; it gives branches to the left atrium and ventricle. There is a free anastomosis between the minute branches of
the two coronary arteries in the substance of the heart.
Peculiarities. - These vessels occasionally arise by a common trunk, or their number may be increased to three, the additional branch being of small size. More rarely, there are two additional branches.
The Arch of the Aorta (Arcus AortAE; Transverse Aorta). - The arch of the aorta begins at the level of the upper border of
the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea and finally passes downward on the left side of the body of
the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta. It thus forms
two curvatures: one with its convexity upward, the other with its convexity forward and to the left. Its upper border is usually about 2.5 cm. below the superior border to the manubrium sterni.
Relations. - The arch of the aorta is covered anteriorly by the pleurae and anterior margins of the lungs, and by the remains
of the thymus. As the vessel runs backward its left side is in contact with the left lung and pleura. Passing downward on the
left side of this part of the arch are four nerves; in order from before backward these are, the left phrenic, the lower of the
superior cardiac branches of the left vagus, the superior cardiac branch of the left sympathetic, and the trunk of the left vagus. As the last nerve crosses the arch it gives off its recurrent branch, which hooks around below the vessel and then passes upward on its right side. The highest left intercostal vein runs obliquely upward and forward on the left side of the arch,
between the phrenic and vagus nerves. On the right are the deep part of the cardiac plexus, the left recurrent nerve, the
esophagus, and the thoracic duct; the trachea lies behind and to the right of the vessel. Above are the innominate, left common carotid, and left subclavian arteries, which arise from the convexity of the arch and are crossed close to their origins
by the left innominate vein. Below are the bifurcation of the pulmonary artery, the left bronchus, the ligamentum arteriosum, the superficial part of the cardiac plexus, and the left recurrent nerve. As already stated, the ligamentum arteriosum
connects the commencement of the left pulmonary artery to the aortic arch.
Between the origin of the left subclavian artery and the attachment of the ductus arteriosus the lumen of the fetal aorta is
considerably narrowed, forming what is termed the aortic isthmus, while immediately beyond the ductus arteriosus the vessel presents a fusiform dilation which His has named the aortic spindle - the point of junction of the two parts being marked
in the concavity of the arch by an indentation or angle. These conditions persist, to some extent, in the adult, where His
found that the average diameter of the spindle exceeded that of the isthmus by 3 mm.
Distinct from this diffuse and moderate stenosis at the isthmus is the condition known as coarctation of the aorta, or
marked stenosis often amounting to complete obliteration of its lumen, seen in adults and occuring at or near, oftenest a
little below, the insertion of the ligamentum arteriosum into the aorta. According to Bonnet 96 this coarctation is never
found in the fetus or at birth, and is due to an abnormal extension of the peculiar tissue of the ductus into the aortic wall,
which gives rise to a simultaneous stenosis of both vessels as it contracts after birth - the ductus is usually obliterated in
these cases. An extensive collateral circulation is set up, by the costocervicals, internal mammaries, and the descending
branches of the transverse cervical above the stenosis, and below it by the first four aortic intercostals, the pericardiacophrenics, and the superior and inferior epigastrics.
Peculiarities. - The height to which the aorta rises in the thorax is usually about 2.5 cm. below the upper border of the sternum; but it may ascend nearly to the top of the bone. Occasionally it is found 4 cm., more rarely from 5 to 8 cm. below this
point. Sometimes the aorta arches over the root of the right lung (right aortic arch) instead of over that of the left, and passes down on the right side of the vertebral column, a condition which is found in birds. In such cases all the thoracic and
abdominal viscera are transposed. Less frequently the aorta, after arching over the root of the right lung, is directed to its
usual position on the left side of the vertebral column; this peculiarity is not accompanied by transposition of the viscera.
The aorta occasionally divides, as in some quadrupeds, into an ascending and a descending trunk, the former of which is
directed vertically upward, and subdivides into three branches, to supply the head and upper extremities. Sometimes the
aorta subdivides near its origin into two branches, which soon reunite. In one of these cases the esophagus and trachea were
found to pass through the interval between the two branches; this is the normal condition of the vessel in the reptilia.
Branches. - The branches given off from the arch of the aorta are three in number: the innominate, the left common carotid,
and the left subclavian.
Peculiarities. - Position of the Branches. - The branches, instead of arising from the highest part of the arch, may spring
from the commencement of the arch or upper part of the ascending aorta; or the distance between them at their origins may
be increased or diminished, the most frequent change in this respect being the approximation of the left carotid toward the
innominate artery.
The number of the primary branches may be reduced to one, or more commonly two; the left carotid arising from the
innominate artery; or (more rarely) the carotid and subclavian arteries of the left side arising from a left innominate artery.
But the number may be increased to four, from the right carotid and subclavian arteries arising directly from the aorta, the
innominate being absent. In most of these latter cases the right subclavian has been found to arise from the left end of the
arch; in other cases it is the second or third branch given off, instead of the first. Another common form in which there are
four primary branches is that in which the left vertebral artery arises from the arch of the aorta between the left carotid and
subclavian arteries. Lastly, the number of trunks from the arch may be increased to five or six; in these instances, the external and internal carotids arise separately from the arch, the common carotid being absent on one or both sides. In some few
cases six branches have been found, and this condition is associated with the origin of both vertebral arteries from the arch.
Number Usual, Arrangement Different. - When the aorta arches over to the right side, the three branches have an arrangement the reverse of what is usual; the innominate artery is a left, one, and the right carotid and subclavian arise separately.
In other cases, where the aorta takes its usual course, the two carotids may be joined in a common trunk, and the subclavians arise separately from the arch, the right subclavian generally arising from the left end of the arch.
In some instances other arteries spring from the arch of the aorta. Of these the most common are the bronchial, one or
both, and the thyreoidea ima; but the internal mammary and the inferior thyroid have been seen to arise from this vessel.
The Innominate Artery (A. Anonyma; Brachiocephalic Artery). - The innominate artery is the largest branch of the arch of
the aorta, and is from 4 to 5 cm. in length. It arises, on a level with the upper border of the second right costal cartilage,
from the commencement of the arch of the aorta, on a plane anterior to the origin of the left carotid; it ascends obliquely
upward, backward, and to the right to the level of the upper border of the right sternoclavicular articulation, where it divides into the right common carotid and right subclavian arteries.
Relations. - Anteriorly, it is separated from the manubrium sterni by the Sternohyoideus and Sternothyreoideus, the remains
of the thymus, the left innominate and right inferior thyroid veins which cross its root, and sometimes the superior cardiac
branches of the right vagus. Posterior to it is the trachea, which it crosses obliquely. On the right side are the right innominate vein, the superior vena cava, the right phrenic nerve, and the pleura; and on the left side, the remains of the thymus, the
origin of the left common carotid artery, the inferior thyroid veins, and the trachea.
Branches. - The innominate artery usually gives off no branches; but occasionally a small branch, the thyreoidea ima, arises
from it. Sometimes it gives off a thymic or bronchial branch.
The thyreoidea ima (a. thyreoidea ima) ascends in front of the trachea to the lower part of the thyroid gland, which it supplies. It varies greatly in size, and appears to compensate for deficiency or absence of one of the other thyroid vessels. It
occasionally arises from the aorta, the right common carotid, the subclavian or the internal mammary.
Point of Division. - The innominate artery sometimes divides above the level of the sternoclavicular joint, less frequently
below it. Position. - When the aortic arch is on the right side, the innominate is directed to the left side of the neck. 23
Collateral Circulation. - Allan Burns demonstrated, on the dead subject, the possibility of the establishment of the collateral circulation after ligature of the innominate artery, by tying and dividing that artery. He then found that “Even coarse
injection, impelled into the aorta, passed freely by the anastomosing branches into the arteries of the right arm, filling them
and all the vessels of the head completely.” The branches by which this circulation would be carried on are very numerous;
thus, all the communications across the middle line between the branches of the carotid arteries of opposite sides would be
available for the supply of blood to the right side of the head and neck; while the anastomosis between the costocervical of
the subclavian and the first aortic intercostal (see infra on the collateral circulation after obliteration of the thoracic aorta)
would bring the blood, by a free and direct course, into the right subclavian. The numerous connections, also, between the
intercostal arteries and the branches of the axillary and internal mammary arteries would, doubtless, assist in the supply of
blood to the right arm, while the inferior epigastric from the external iliac would, by means of its anastomosis with the internal mammary, compensate for any deficiency in the vascularity of the wall of the chest.
The Subclavian Artery (A. Subclavia). - On the right side the subclavian artery arises from the innominate artery behind the
right sternoclavicular articulation; on the left side it springs from the arch of the aorta. The two vessels, therefore, in the
first part of their course, differ in length, direction, and relation with neighboring structures.
In order to facilitate the description, each subclavian artery is divided into three parts. The first portion extends from the
origin of the vessel to the medial border of the Scalenus anterior; the second lies behind this muscle; and the third extends
from the lateral margin of the muscle to the outer border of the first rib, where it becomes the axillary artery. The first portions of the two vessels require separate descriptions; the second and third parts of the two arteries are practically alike.
First Part of the Right Subclavian Artery. - The first part of the right subclavian artery arises from the innominate artery,
behind the upper part of the right sternoclavicular articulation, and passes upward and lateralward to the medial margin of
the Scalenus anterior. It ascends a little above the clavicle, the extent to which it does so varying in different cases.
Relations. - It is covered, in front, by the integument, superficial fascia, Platysma, deep fascia, the clavicular origin of the
Sternocleidomastoideus, the Sternohyoideus, and Sternothyreoideus, and another layer of the deep fascia. It is crossed by
the internal jugular and vertebral veins, by the vagus nerve and the cardiac branches of the vagus and sympathetic, and by
the subclavian loop of the sympathetic trunk which forms a ring around the vessel. The anterior jugular vein is directed
lateralward in front of the artery, but is separated from it by the Sternohyoideus and Sternothyreoideus. Below and behind
the artery is the pleura, which separates it from the apex of the lung; behind is the sympathetic trunk, the Longus collie and
the first thoracic vertebra. The right recurrent nerve winds around the lower and back part of the vessel.
First Part of the Left Subclavian Artery. - The first part of the left subclavian artery arises from the arch of the aorta, behind
the left common carotid, and at the level of the fourth thoracic vertebra; it ascends in the superior mediastinal cavity to the
root of the neck and then arches lateralward to the medial border of the Scalenus anterior.
Relations. - It is in relation, in front, with the vagus, cardiac, and phrenic nerves, which lie parallel with it, the left common
carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein, and is covered
by the Sternothyreoideus, Sternohyoideus, and Sternocleidomastoideus; behind, it is in relation with the esophagus, thoracic duct, left recurrent nerve, inferior cervical ganglion of the sympathetic trunk, and Longus colli; higher up, however, the
esophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. Medial to it are the esophagus, trachea, thoracic duct, and left recurrent
nerve; lateral to it, the left pleura and lung.
Second and Third Parts of the Subclavian Artery. - The second portion of the subclavian artery lies behind the Scalenus
anterior; it is very short, and forms the highest part of the arch described by the vessel.
Relations. - It is covered, in front, by the skin, superficial fascia, Platysma, deep cervical fascia, Sternocleidomastoideus,
and Scalenus anterior. On the right side of the neck the phrenic nerve is separated from the second part of the artery by the
Scalenus anterior, while on the left side it crosses the first part of the artery close to the medial edge of the muscle. Behind
the vessel are the pleura and the Scalenus medius; above, the brachial plexus of nerves; below, the pleura. The subclavian
vein lies below and in front of the artery, separated from it by the Scalenus anterior.
The third portion of the subclavian artery runs downward and lateralward from the lateral margin of the Scalenus anterior
to the outer border of the first rib, where it becomes the axillary artery. This is the most superficial portion of the vessel,
and is contained in the subclavian triangle
Relations. - It is covered, in front, by the skin, the superficial fascia, the Platysma, the supraclavicular nerves, and the deep
cervical fascia. The external jugular vein crosses its medial part and receives the transverse scapular, transverse cervical,
and anterior jugular veins, which frequently form a plexus in front of the artery. Behind the veins, the nerve to the Subclavius descends in front of the artery. The terminal part of the artery lies behind the clavicle and the Subclavius and is crossed
by the transverse scapular vessels. The subclavian vein is in front of and at a slightly lower level than the artery. Behind, it
lies on the lowest trunk of the brachial plexus, which intervenes between it and the Scalenus medius. Above and to its lateral side are the upper trunks of the brachial plexus and the Omohyoideus. Below, it rests on the upper surface of the first
rib.
Peculiarities. - The subclavian arteries vary in their origin, their course, and the height to which they rise in the neck.
The origin of the right subclavian from the innominate takes place, in some cases, above the sternoclavicular articulation,
and occasionally, but less frequently, below that joint. The artery may arise as a separate trunk from the arch of the aorta,
and in such cases it may be either the first, second, third, or even the last branch derived from that vessel; in the majority,
however, it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary position of the
innominate artery; when the second or third, it gains its usual position by passing behind the right carotid; and when the last
branch, it arises from the left extremity of the arch, and passes obliquely toward the right side, usually behind the trachea,
esophagus, and right carotid, sometimes between the esophagus and trachea, to the upper border of the first rib, whence it
follows its ordinary course. In very rare instances, this vessel arises from the thoracic aorta, as low down as the fourth tho-
racic vertebra. Occasionally, it perforates the Scalenus anterior; more rarely it passes in front of that muscle. Sometimes the
subclavian vein passes with the artery behind the Scalenus anterior. The artery may ascend as high as 4 cm. above the clavicle, or any intermediate point between this and the upper border of the bone, the right subclavian usually ascending higher
than the left.
The left subclavian is occasionally joined at its origin with the left carotid. The left subclavian artery is more deeply
placed than the right in the first part of its course, and, as a rule, does not reach quite as high a level in the neck. The posterior border of the Sternocleidomastoideus corresponds pretty closely to the lateral border of the Scalenus anterior, so that
the third portion of the artery, the part most accessible for operation, lies immediately lateral to the posterior border of the
Sternocleidomastoideus.
Collateral Circulation. - After ligature of the third part of the subclavian artery, the collateral circulation is established
mainly by three sets of vessels, thus described in a dissection:
1. A posterior set, consisting of the transverse scapular and the descending ramus of the transverse cervical branches of
the subclavian, anastomosing with the subscapular from the axillary.
2. A medial set, produced by the connection of the internal mammary on the one hand, with the highest intercostal and
lateral thoracic arteries, and the branches from the subscapular on the other.
3. A middle or axillary set, consisting of a number of small vessels derived from branches of the subclavian, above, and,
passing through the axilla, terminating either in the main trunk, or some of the branches of the axillary below. This last set
presented most conspicuously the peculiar character of newly formed or, rather, dilated arteries, being excessively tortuous,
and forming a complete plexus.
The chief agent in the restoration of the axillary artery below the tumor was the subscapular artery, which communicated
most freely with the internal mammary, transverse scapular and descending ramus of the transverse cervical branches of the
subclavian, from all of which it received so great an influx of blood as to dilate it to three times its natural size.
When a ligature is applied to the first part of the subclavian artery, the collateral circulation is carried on by: (1) the anastomosis between the superior and inferior thyroids; (2) the anastomosis of the two vertebrals; (3) the anastomosis of the
internal mammary with the inferior epigastric and the aortic intercostals; (4) the costocervical anastomosing with the aortic
intercostals; (5) the profunda cervicis anastomosing with the descending branch of the occipital; (6) the scapular branches
of the thyrocervical trunk anastomosing with the branches of the axillary, and (7) the thoracic branches of the axillary anastomosing with the aortic intercostals.
The branches of the subclavian artery are: Vertebral. Internal mammary.
Thyrocervical. Costocervical.
On the left side all four branches generally arise from the first portion of the vessel; but on the right side the costocervical
trunk usually springs from the second portion of the vessel. On both sides of the neck, the first three branches arise close
together at the medial border of the Scalenus anterior; in the majority of cases, a free interval of from 1.25 to 2.5 cm. exists
between the commencement of the artery and the origin of the nearest branch.
The internal mammary artery (a. mammaria interna) arises from the under surface of the first portion of the subclavian,
opposite the thyrocervical trunk. It descends behind the cartilages of the upper six ribs at a distance of about 1.25 cm. from
the margin of the sternum, and at the level of the sixth intercostal space divides into the musculophrenic and superior epigastric arteries.
Relations. - It is directed at first downward, forward, and medialward behind the sternal end of the clavicle, the subclavian
and internal jugular veins, and the first costal cartilage, and passes forward close to the lateral side of the innominate vein.
As it enters the thorax the phrenic nerve crosses from its lateral to its medial side. Below the first costal cartilage it descends almost vertically to its point of bifurcation. It is covered in front by the cartilages of the upper six ribs and the intervening Intercostales interni and anterior intercostal membranes, and is crossed by the terminal portions of the upper six
intercostal nerves. It rests on the pleura, as far as the third costal cartilage; below this level, upon the Transversus thoracis.
It is accompanied by a pair of veins; these unite above to form a single vessel, which runs medial to the artery and ends in
the corresponding innominate vein.
The branches of the internal mammary are:
Pericardiacophrenic.
Intercostal.
Anterior Mediastinal.
Perforating.
Pericardial.
Musculophrenic.
Sternal.
Superior Epigastric.
The Pericardiacophrenic Artery (a. pericardiacophrenica; a. comes nervi phrenici) is a long slender branch, which accompanies the phrenic nerve, between the pleura and pericardium, to the diaphragm, to which it is distributed; it anastomoses
with the musculophrenic and inferior phrenic arteries.
The Anterior Mediastinal Arteries (aa. mediastinales anteriores; mediastinal arteries) are small vessels, distributed to the
areolar tissue and lymph glands in the anterior mediastinal cavity, and to the remains of the thymus.
The Pericardial Branches supply the upper part of the anterior surface of the pericardium; the lower part receives branches
from the musculophrenic artery.
The Sternal Branches (rami sternales) are distributed to the Transversus thoracis, and to the posterior surface of the sternum.
The anterior mediastinal, pericardial, and sternal branches, together with some twigs from the pericardiacophrenic, anastomose with branches from the intercostal and bronchial arteries, and form a subpleural mediastinal plexus.
The Intercoastal Branches (rami intercostales; anterior intercostal arteries) supply the upper five or six intercostal spaces.
Two in number in each space, these small vessels pass lateralward, one lying near the lower margin of the rib above, and
the other near the upper margin of the rib below, and anastomose with the intercostal arteries from the aorta. They are at
first situated between the pleura and the Intercostales interni, and then between the Intercostales interni and externi. They
supply the Intercostales and, by branches which perforate the Intercostales externi, the Pectorales and the mamma.
The Perforating Branches (rami perforantes) correspond to the five or six intercostal spaces. They pass forward through
the intercostal spaces, and, curving lateralward, supply the Pectoralis major and the integument. Those which correspond to
the second, third, and fourth spaces give branches to the mamma, and during lactation are of large size.
The Musculophrenic Artery (a. musculophrenica) is directed obliquely downward and lateralward, behind the cartilages of
the false ribs; it perforates the diaphragm at the eighth or ninth costal cartilage, and ends, considerably reduced in size, opposite the last intercostal space. It gives off intercostal branches to the seventh, eighth, and ninth intercostal spaces; these
diminish in size as the spaces decrease in length, and are distributed in a manner precisely similar to the intercostals from
the internal mammary. The musculophrenic also gives branches to the lower part of the pericardium, and others which run
backward to the diaphragm, and downward to the abdominal muscles.
The Superior Epigastric Artery (a. epigastrica superior) continues in the original direction of the internal mammary; it
descends through the interval between the costal and sternal attachments of the diaphragm, and enters the sheath of the
Rectus abdominis, at first lying behind the muscle, and then perforating and supplying it, and anastomosing with the inferior epigastric artery from the external iliac. Branches perforate the anterior wall of the sheath of the Rectus, and supply the
muscles of the abdomen and the integument, and a small branch passes in front of the xiphoid process and anastomoses
with the artery of the opposite side. It also gives some twigs to the diaphragm, while from the artery of the right side small
branches extend into the falciform ligament of the liver and anastomose with the hepatic artery.
The costocervical trunk (truncus costocervicalis; superior intercostal artery) arises from the upper and back part of the subclavian artery, behind the Scalenus anterior on the right side, and medial to that muscle on the left side. Passing backward,
it gives off the profunda cervicalis, and, continuing as the highest intercostal artery, descends behind the pleura in front of
the necks of the first and second ribs, and anastomoses with the first aortic intercostal. As it crosses the neck of the first rib
it lies medial to the anterior division of the first thoracic nerve, and lateral to the first thoracic ganglion of the sympathetic
trunk.
In the first intercostal space, it gives off a branch which is distributed in a manner similar to the distribution of the aortic
intercostals. The branch for the second intercostal space usually joins with one from the highest aortic intercostal artery.
This branch is not constant, but is more commonly found on the right side; when absent, its place is supplied by an intercostal branch from the aorta. Each intercostal gives off a posterior branch which goes to the posterior vertebral muscles,
and sends a small spinal branch through the corresponding intervertebral foramen to the medulla spinalis and its membranes.
The Profunda Cervicalis (a. cervicalis profunda; deep cervical branch) arises, in most cases, from the costocervical trunk,
and is analogous to the posterior branch of an aortic intercostal artery: occasionally it is a separate branch from the subclavian artery. Passing backward, above the eighth cervical nerve and between the transverse process of the seventh cervical
vertebra and the neck of the first rib, it runs up the back of the neck, between the Semispinales capitis and colli, as high as
the axis vertebra, supplying these and adjacent muscles, and anastomosing with the deep division of the descending branch
of the occipital, and with branches of the vertebral. It gives off a spinal twig which enters the canal through the intervertebral foramen between the seventh cervical and first thoracic vertebrae.
The axillary artery, the continuation of the subclavian, commences at the outer border of the first rib, and ends at the lower
border of the tendon of the Teres major, where it takes the name of brachial. Its direction varies with the position of the
limb; thus the vessel is nearly straight when the arm is directed at right angles with the trunk, concave upward when the
arm is elevated above this, and convex upward and lateralward when the arm lies by the side. At its origin the artery is very
deeply situated, but near its termination is superficial, being covered only by the skin and fascia. To facilitate the description of the vessel it is divided into three portions; the first part lies above, the second behind, and the third below the Pectoralis minor.
Relations. - The first portion of the axillary artery is covered anteriorly by the clavicular portion of the Pectoralis major and
the coracoclavicular fascia, and is crossed by the lateral anterior thoracic nerve, and the thoracoacromial and cephalic
veins; posterior to it are the first intercostal space, the corresponding Intercostalis externus, the first and second digitations
of the Serratus anterior, and the long thoracic and medial anterior thoracic nerves, and the medial cord of the brachial plexus; on its lateral side is the brachial plexus, from which it is separated by a little areolar tissue; on its medial, or thoracic
side, is the axillary vein which overlaps the artery. It is enclosed, together with the axillary vein and the brachial plexus, in
a fibrous sheath - the axillary sheath - continuous above with the deep cervical fascia.
The second portion of the axillary artery is covered, anteriorly, by the Pectorales major and minor; posterior to it are the
posterior cord of the brachial plexus, and some areolar tissue which intervenes between it and the Subscapularis; on the
medial side is the axillary vein, separated from the artery by the medial cord of the brachial plexus and the medial anterior
thoracic nerve; on the lateral side is the lateral cord of the brachial plexus. The brachial plexus thus surrounds the artery on
three sides, and separates it from direct contact with the vein and adjacent muscles.
The third portion of the axillary artery extends from the lower border of the Pectoralis minor to the lower border of the
tendon of the Teres major. In front, it is covered by the lower part of the Pectoralis major above, but only by the integument
and fascia below; behind, it is in relation with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi
and Teres major; on its lateral side is the Coracobrachialis, and on its medial or thoracic side, the axillary vein. The nerves
of the brachial plexus bear the following relations to this part of the artery: on the lateral side are the lateral head and the
trunk of the median, and the musculocutaneous for a short distance; on the medial side the ulnar (between the vein and artery) and medial brachial cutaneous (to the medial side of the vein); in front are the medial head of the median and the me-
dial antibrachial cutaneous, and behind, the radial and axillary, the latter only as far as the lower border of the Subscapularis.
Collateral Circulation after Ligature of the Axillary Artery. - If the artery be tied above the origin of the thoracoacromial,
the collateral circulation will be carried on by the same branches as after the ligature of the third part of the subclavian; if at
a lower point, between the thoracoacromial and the subscapular, the latter vessel, by its free anastomosis with the transverse scapular and transverse cervical branches of the subclavian, will become the chief agent in carrying on the circulation; the lateral thoracic, if it be below the ligature, will materially contribute by its anastomoses with the intercostal and
internal mammary arteries. If the point included in the ligature is below the origin of the subscapular artery, it will most
probably also be below the origins of the two humeral circumflex arteries. The chief agents in restoring the circulation will
then be the subscapular and the two humeral circumflex arteries anastomosing with the a. profunda brachii.
Branches. - The branches of the axillary are:
From first part, - Highest Thoracic.
From second part - Thoracoacromial. Lateral Thoracic.
From third part - Subscapular.
Posterior Humeral Circumflex.
Anterior Humeral Circumflex.
1. The highest thoracic artery (a. thoracalis suprema; superior thoracic artery) is a small vessel, which may arise from the
thoracoacromial. Running forward and medialward along the upper border of the Pectoralis minor, it passes between it and
the Pectoralis major to the side of the chest. It supplies branches to these muscles, and to the parietes of the thorax, and
anastomoses with the internal mammary and intercostal arteries.
2. The thoracoacromial artery (a. thoracoacromialis; acromiothoracic artery; thoracic axis) is a short trunk, which arises
from the forepart of the axillary artery, its origin being generally overlapped by the upper edge of the Pectoralis minor Projecting forward to the upper border of this muscle, it pierces the coracoclavicular fascia and divides into four branches pectoral, acromial, clavicular, and deltoid. The pectoral branch descends between the two Pectorales, and is distributed to
them and to the mamma, anastomosing with the intercostal branches of the internal mammary and with the lateral thoracic.
The acromial branch runs lateralward over the coracoid process and under the Deltoideus, to which it gives branches; it
then pierces that muscle and ends on the acromion in an arterial network formed by branches from the transverse scapular,
thoracoacromial, and posterior humeral circumflex arteries. The clavicular branch runs upward and medialward to the sternoclavicular joint, supplying this articulation, and the Subclavius. The deltoid (humeral) branch, often arising with the
acromial, crosses over the Pectoralis minor and passes in the same groove as the cephalic vein, between the Pectoralis major and Deltoideus, and gives branches to both muscles.
3. The lateral thoracic artery (a. thoracalis lateralis; long thoracic artery; external mammary artery) follows the lower border of the Pectoralis minor to the side of the chest, supplying the Serratus anterior and the Pectoralis, and sending branches
across the axilla to the axillary glands and Subscapularis; it anastomoses with the internal mammary, subscapular, and intercostal arteries, and with the pectoral branch of the thoracoacromial. In the female it supplies an external mammary
branch which turns round the free edge of the Pectoralis major and supplies the mamma.
4. The subscapular artery (a. subscapularis) the largest branch of the axillary artery, arises at the lower border of the Subscapularis, which it follows to the inferior angle of the scapula, where it anastomoses with the lateral thoracic and intercostal arteries and with the descending branch of the transverse cervical, and ends in the neighboring muscles. About 4 cm.
from its origin it gives off a branch, the scapular circumflex artery.
The Scapular Circumflex Artery (a. circumflexa scapulae; dorsalis scapulae artery) is generally larger than the continuation of the subscapular. It curves around the axillary border of the scapula, traversing the space between the Subscapularis
above, the Teres major below, and the long head of the Triceps laterally; it enters the infraspinatous fossa under cover of
the Teres minor, and anastomoses with the transverse scapular artery and the descending branch of the transverse cervical.
In its course it gives off two branches: one (infrascapular) enters the subscapular fossa beneath the Subscapularis, which it
supplies, anastomosing with the transverse scapular artery and the descending branch of the transverse cervical; the other is
continued along the axillary border of the scapula, between the Teres major and minor, and at the dorsal surface of the inferior angle anastomoses with the descending branch of the transverse cervical. In addition to these, small branches are distributed to the back part of the Deltoideus and the long head of the Triceps brachii, anastomosing with an ascending branch
of the a. profunda brachii.
5. The posterior humeral circumflex artery (a. circumflexa humeri posterior; posterior circumflex artery) arises from the
axillary artery at the lower border of the Subscapularis, and runs backward with the axillary nerve through the quadrangular
space bounded by the Subscapularis and Teres minor above, the Teres major below, the long head of the Triceps brachii
medially, and the surgical neck of the humerus laterally. It winds around the neck of the humerus and is distributed to the
Deltoideus and shoulder-joint, anastomosing with the anterior humeral circumflex and profunda brachii.
6. The anterior humeral circumflex artery (a. circumflexa humeri anterior; anterior circumflex artery), considerably smaller than the posterior, arises nearly opposite it, from the lateral side of the axillary artery. It runs horizontally, beneath the
Coracobrachialis and short head of the Biceps brachii, in front of the neck of the humerus. On reaching the intertubercular
sulcus, it gives off a branch which ascends in the sulcus to supply the head of the humerus and the shoulder-joint. The trunk
of the vessel is then continued onward beneath the long head of the Biceps brachii and the Deltoideus, and anastomoses
with the posterior humeral circumflex artery.
Peculiarities. - The branches of the axillary artery vary considerably in different subjects. Occasionally the subscapular,
humeral circumflex, and profunda arteries arise from a common trunk, and when this occurs the branches of the brachial
plexus surround this trunk instead of the main vessel. Sometimes the axillary artery divides into the radial and ulnar arteries, and occasionally it gives origin to the volar interosseous artery of the forearm.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 29. Thoracic part of aorta: relations, branches, supplement.
The aim: to learn the structure and relations of aorta and its main branches.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The descending aorta is divided into two portions, the thoracic and abdominal, in correspondence with the two great cavities of the trunk in which it is situated
The Thoracic Aorta - (Aorta Thoracalis) is contained in the posterior mediastinal cavity. It begins at the lower border of the
fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth at
the aortic hiatus in the diaphragm. At its commencement, it is situated on the left of the vertebral column; it approaches the
median line as it descends; and, at its termination, lies directly in front of the column. The vessel describes a curve which is
concave forward, and as the branches given off from it are small, its diminution in size is inconsiderable.
Relations. - It is in relation, anteriorly, from above downward, with the root of the left lung, the pericardium, the esophagus, and the diaphragm; posteriorly, with the vertebral column and the hemiazygos veins; on the right side, with the azygos
vein and thoracic duct; on the left side, with the left pleura and lung. The esophagus, with its accompanying plexus of
nerves, lies on the right side of the aorta above; but at the lower part of the thorax it is placed in front of the aorta, and,
close to the diaphragm, is situated on its left side.
Peculiarities. - The aorta is occasionally found to be obliterated at the junction of the arch with the thoracic aorta, just below the ductus arteriosus. Whether this is the result of disease, or of congenital malformation, is immaterial to our present
purpose; it affords an interesting opportunity of observing the resources of the collateral circulation. The course of the anastomosing vessels, by which the blood is brought from the upper to the lower part of the artery, will be found well described
in an account of two cases in the Pathological Transactions, vols. viii and x. In the former, Sydney Jones thus sums up the
detailed description of the anastomosing vessels: The principal communications by which the circulation was carried on
were: (1) The internal mammary, anastomosing with the intercostal arteries, with the inferior phrenic of the abdominal aorta by means of the musculophrenic and pericardiacophrenic, and largely with the inferior epigastric. (2) The costocervical
trunk, anastomosing anteriorly by means of a large branch with the first aortic intercostal, and posteriorly with the posterior
branch of the same artery. (3) The inferior thyroid, by means of a branch about the size of an ordinary radial, forming a
communication with the first aortic intercostal. (4) The transverse cervical, by means of very large communications with
the posterior branches of the intercostals. (5) The branches (of the subclavian and axillary) going to the side of the chest
were large, and anastomosed freely with the lateral branches of the intercostals. In the second case Wood describes the
anastomoses in a somewhat similar manner, adding the remark that “the blood which was brought into the aorta through the
anastomosis of the intercostal arteries appeared to be expended principally in supplying the abdomen and pelvis; while the
supply to the lower extremities had passed through the internal mammary and epigastrics.”
In a few cases an apparently double descending thoracic aorta has been found, the two vessels lying side by side, and
eventually fusing to form a single tube in the lower part of the thorax or in the abdomen. One of them is the aorta, the other
represents a dissecting aortic aneurism which has become canalized; opening above and below into the true aorta, and at
first sight presenting the appearances of a proper bloodvessel.
Branches of the Thoracic Aorta. - 6
Pericardial
Intercostal
Bronchial
Subcostal
Visceral
Parietal
Esophageal
Superior Phrenic
Mediastinal
The pericardial branches (rami pericardiaci) consist of a few small vessels which are distributed to the posterior surface of
the pericardium.
The bronchial arteries (aa. bronchiales) vary in number, size, and origin. There is as a rule only one right bronchial artery,
which arises from the first aortic intercostal, or from the upper left bronchial artery. The left bronchial arteries are usually
two in number, and arise from the thoracic aorta. The upper left bronchial arises opposite the fifth thoracic vertebra, the
lower just below the level of the left bronchus. Each vessel runs on the back part of its bronchus, dividing and subdividing
along the bronchial tubes, supplying them, the areolar tissue of the lungs, the bronchial lymph glands, and the esophagus.
The esophageal arteries (aa. aesophageae) four or five in number, arise from the front of the aorta, and pass obliquely
downward to the esophagus, forming a chain of anastomoses along that tube, anastomosing with the esophageal branches
of the inferior thyroid arteries above, and with ascending branches from the left inferior phrenic and left gastric arteries
below.
The mediastinal branches (rami mediastinales) are numerous small vessels which supply the lymph glands and loose areolar tissue in the posterior mediastinum.
Intercostal Arteries (aa. intercostales). - There are usually nine pairs of aortic intercostal arteries. They arise from the back
of the aorta, and a redistributed to the lower nine intercostal spaces, the first two spaces being supplied by the highest intercostal artery, a branch of the costocervical trunk of the subclavian. The right aortic intercostals are longer than the left, on
account of the position of the aorta on the left side of the vertebral column; they pass across the bodies of the vertebrae behind the esophagus, thoracic duct, and vena azygos, and are covered by the right lung and pleura. The left aortic intercostals
run backward on the sides of the vertebrae and are covered by the left lung and pleura; the upper two vessels are crossed by
the highest left intercostal vein, the lower vessels by the hemiazygos veins. The further course of the intercostal arteries is
practically the same on both sides. Opposite the heads of the ribs the sympathetic trunk passes downward in front of them,
and the splanchnic nerves also descend in front by the lower arteries. Each artery then divides into an anterior and a posterior ramus.
The Anterior Ramus crosses the corresponding intercostal space obliquely toward the angle of the upper rib, and thence is
continued forward in the costal groove. It is placed at first between the pleura and the posterior intercostal membrane, then
it pierces this membrane, and lies between it and the Intercostalis externus as far as the angle of the rib; from this onward it
runs between the Intercostales externus and internus, and anastomoses in front with the intercostal branch of the internal
mammary or musculophrenic. Each artery is accompanied by a vein and a nerve, the former being above and the latter below the artery, except in the upper spaces, where the nerve is at first above the artery. The first aortic intercostal artery
anastomoses with the intercostal branch of the costocervical trunk, and may form the chief supply of the second intercostal
space. The lower two intercostal arteries are continued anteriorly from the intercostal spaces into the abdominal wall, and
anastomose with the subcostal, superior epigastric, and lumbar arteries.
- The anterior rami give off the following branches:
Collateral Intercostal.
Lateral Cutaneous.
Muscular.
Mammary.
The collateral intercostal branch comes off from the intercostal artery near the angle of the rib, and descends to the upper
border of the rib below, along which it courses to anastomose with the intercostal branch of the internal mammary.
Muscular branches are given to the Intercostales and Pectorales and to the Serratus anterior; they anastomose with the
highest and lateral thoracic branches of the axillary artery.
The lateral cutaneous branches accompany the lateral cutaneous branches of the thoracic nerves.
Mammary branches are given off by the vessels in the third, fourth, and fifth spaces. They supply the mamma, and increase considerably in size during the period of lactation.
The Posterior Ramus runs backward through a space which is bounded above and below by the necks of the ribs, medially
by the body of a vertebra, and laterally by an anterior costotransverse ligament. It gives off a spinal branch which enters the
vertebral canal through the intervertebral foramen and is distributed to the medulla spinalis and its membranes and the vertebrae. It then courses over the transverse process with the posterior division of the thoracic nerve, supplies branches to the
muscles of the back and cutaneous branches which accompany the corresponding cutaneous branches of the posterior division of the nerve.
The subcostal arteries, so named because they lie below the last ribs, constitute the lowest pair of branches derived from
the thoracic aorta, and are in series with the intercostal arteries. Each passes along the lower border of the twelfth rib behind the kidney and in front of the Quadratus lumborum muscle, and is accompanied by the twelfth thoracic nerve. It then
pierces the posterior aponeurosis of the Transversus abdominis, and, passing forward between this muscle and the Obliquus
internus, anastomoses with the superior epigastric, lower intercostal, and lumbar arteries. Each subcostal artery gives off a
posterior branch which has a similar distribution to the posterior ramus of an intercostal artery.
The superior phrenic branches are small and arise from the lower part of the thoracic aorta; they are distributed to the posterior part of the upper surface of the diaphragm, and anastomose with the musculophrenic and pericardiacophrenic arteries.
A small aberrant artery is sometimes found arising from the right side of the thoracic aorta near the origin of the right
bronchial. It passes upward and to the right behind the trachea and the esophagus, and may anastomose with the highest
right intercostal artery. It represents the remains of the right dorsal aorta, and in a small proportion of cases is enlarged to
form the first part of the right subclavian artery.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 30. System of veins of the superior vena cava.
The aim: to learn the structure and relations of veins composing the superior vena cava system..
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The veins of the upper extremity are divided into two sets, superficial and deep; the two sets anastomose frequently with
each other. The superficial veins are placed immediately beneath the integument between the two layers of superficial fascia. The deep veins accompany the arteries, and constitute the venae comitantes of those vessels. Both sets are provided
with valves, which are more numerous in the deep than in the superficial veins.
The Superficial Veins of the Upper Extremity
The superficial veins of the upper extremity are the digital, metacarpal, cephalic, basilic, median.
Digital Veins. - The dorsal digital veins pass along the sides of the fingers and are joined to one another by oblique communicating branches. Those from the adjacent sides of the fingers unite to form three dorsal metacarpal veins, which end in
a dorsal venous net-work opposite the middle of the metacarpus. The radial part of the net-work is joined by the dorsal digital vein from the radial side of the index finger and by the dorsal digital veins of the thumb, and is prolonged upward as the
cephalic vein. The ulnar part of the net-work receives the dorsal digital vein of the ulnar side of the little finger and is continued upward as the basilic vein. A communicating branch frequently connects the dorsal venous network with the cephalic vein about the middle of the forearm.
The volar digital veins on each finger are connected to the dorsal digital veins by oblique intercapitular veins. They drain
into a venous plexus which is situated over the thenar and hypothenar eminences and across the front of the wrist.
The cephalic vein begins in the radial part of the dorsal venous net-work and winds upward around the radial border of
the forearm, receiving tributaries from both surfaces. Below the front of the elbow it gives off the vena mediana cubiti (median basilic vein), which receives a communicating branch from the deep veins of the forearm and passes across to join the
basilic vein. The cephalic vein then ascends in front of the elbow in the groove between the Brachioradialis and the Biceps
brachii. It crosses superficial to the musculocutaneous nerve and ascends in the groove along the lateral border of the Biceps brachii. In the upper third of the arm it passes between the Pectoralis major and Deltoideus, where it is accompanied
by the deltoid branch of the thoracoacromial artery. It pierces the coracoclavicular fascia and, crossing the axillary artery,
ends in the axillary vein just below the clavicle. Sometimes it communicates with the external jugular vein by a branch
which ascends in front of the clavicle.
The accessory cephalic vein (v. cephalica accessoria) arises either from a small tributory plexus on the back of the forearm
or from the ulnar side of the dorsal venous net-work; it joins the cephalic below the elbow. In some cases the accessory
cephalic springs from the cephalic above the wrist and joins it again higher up. A large oblique branch frequently connects
the basilic and cephalic veins on the back of the forearm.
The basilic vein (v. basilica) begins in the ulnar part of the dorsal venous network. It runs up the posterior surface of the
ulnar side of the forearm and inclines forward to the anterior surface below the elbow, where it is joined by the vena mediana cubiti. It ascends obliquely in the groove between the Biceps brachii and Pronator teres and crosses the brachial artery,
from which it is separated by the lacertus fibrosus; filaments of the medial antibrachial cutaneous nerve pass both in front
of and behind this portion of the vein. It then runs upward along the medial border of the Biceps brachii, perforates the deep
fascia a little below the middle of the arm, and, ascending on the medial side of the brachial artery to the lower border of
the Teres major, is continued onward as the axillary vein.
The median antibrachial vein (v. mediana antibrachii) drains the venous plexus on the volar surface of the hand. It ascends
on the ulnar side of the front of the forearm and ends in the basilic vein or in the vena mediana cubiti; in a small proportion
of cases it divides into two branches, one of which joins the basilic, the other the cephalic, below the elbow.
The deep veins follow the course of the arteries, forming their venae comitantes. They are generally arranged in pairs, and
are situated one on either side of the corresponding artery, and connected at intervals by short transverse branches.
Deep Veins of the Hand. - The superficial and deep volar arterial arches are each accompanied by a pair of venae comitantes which constitute respectively the superficial and deep volar venous arches, and receive the veins corresponding to the
branches of the arterial arches; thus the common volar digital veins, formed by the union of the proper volar digital veins,
open into the superficial, and the volar metacarpal veins into the deep volar venous arches. The dorsal metacarpal veins
receive perforating branches from the volar metacarpal veins and end in the radial veins and in the superficial veins on the
dorsum of the wrist.
The deep veins of the forearm are the venae comitantes of the radial and ulnar veins and constitute respectively the upward continuations of the deep and superficial volar venous arches; they unite in front of the elbow to form the brachial
veins. The radial veins are smaller than the ulnar and receive the dorsal metacarpal veins. The ulnar veins receive tributaries from the deep volar venous arches and communicate with the superficial veins at the wrist; near the elbow they receive
the volar and dorsal interosseous veins and send a large communicating branch (profunda vein) to the vena mediana cubiti.
The brachial veins (vv. brachiales) are placed one on either side of the brachial artery, receiving tributaries corresponding
with the branches given off from that vessel; near the lower margin of the Subscapularis, they join the axillary vein; the
medial one frequently joins the basilic vein.
These deep veins have numerous anastomoses, not only with each other, but also with the superficial veins.
The axillary vein (v. axillaris) begins at the lower border of the Teres major, as the continuation of the basilic vein, increases in size as it ascends, and ends at the outer border of the first rib as the subclavian vein. Near the lower border of the
Subscapularis it receives the brachial veins and, close to its termination, the cephalic vein; its other tributaries correspond
with the branches of the axillary artery. It lies on the medial side of the artery, which it partly overlaps; between the two
vessels are the medial cord of the brachial plexus, the median, the ulnar, and the medial anterior thoracic nerves. It is provided with a pair of valves opposite the lower border of the Subscapularis; valves are also found at the ends of the cephalic
and subscapular veins.
The subclavian vein (v. subclavia), the continuation of the axillary, extends from the outer border of the first rib to the
sternal end of the clavicle, where it unites with the internal jugular to form the innominate vein. It is in relation, in front,
with the clavicle and Subclavius; behind and above, with the subclavian artery, from which it is separated medially by the
Scalenus anterior and the phrenic nerve. Below, it rests in a depression on the first rib and upon the pleura. It is usually
provided with a pair of valves, which are situated about 2.5 cm. from its termination.
The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and occasionally
passes with this vessel behind the Scalenus anterior.
Tributaries. - This vein receives the external jugular vein, sometimes the anterior jugular vein, and occasionally a small
branch, which ascends in front of the clavicle, from the cephalic. At its angle of junction with the internal jugular, the left
subclavian vein receives the thoracic duct, and the right subclavian vein the right lymphatic duct.
The Veins of the Thorax
The innominate veins (vv. anonymae; brachiocephalic veins) are two large trunks, placed one on either side of the root of
the neck, and formed by the union of the internal jugular and subclavian veins of the corresponding side; they are devoid of
valves.
The Right Innominate Vein (v. anonyma dextra) is a short vessel, about 2.5 cm. in length, which begins behind the sternal
end of the clavicle, and, passing almost vertically downward, joins with the left innominate vein just below the cartilage of
the first rib, close to the right border of the sternum, to form the superior vena cava. It lies in front and to the right of the
innominate artery; on its right side are the phrenic nerve and the pleura, which are interposed between it and the apex of the
lung. This vein, at its commencement, receives the right vertebral vein; and, lower down, the right internal mammary and
right inferior thyroid veins, and sometimes the vein from the first intercostal space.
The Left Innominate Vein (v. anonyma sinistra), about 6 cm. in length, begins behind the sternal end of the clavicle and
runs obliquely downward and to the right behind the upper half of the manubrium sterni to the sternal end of the first right
costal cartilage, where it unites with the right innominate vein to form the superior vena cava. It is separated from the manubrium sterni by the Sternohyoideus and Sternothyreoideus, the thymus or its remains, and some loose areolar tissue. Behind it are the three large arteries, innominate, left common carotid, and left subclavian, arising from the aortic arch, together with the vagus and phrenic nerves. The left innominate vein may occupy a higher level, crossing the jugular notch
and lying directly in front of the trachea.
Tributaries. - Its tributaries are the left vertebral, left internal mammary, left inferior thyroid, and the left highest intercostal
veins, and occasionally some thymic and pericardiac veins.
Peculiarities. - Sometimes the innominate veins open separately into the right atrium; in such cases the right vein takes the
ordinary course of the superior vena cava; the left vein - left superior vena cava, as it is then termed - which may communicate by a small branch with the right one, passes in front of the root of the left lung, and, turning to the back of the heart,
ends in the right atrium. This occasional condition in the adult is due to the persistence of the early fetal condition, and is
the normal state of things in birds and some mammalia.
The internal mammary veins (vv. mammariae internae) are venae comitantes to the lower half of the internal mammary
artery, and receive tributaries corresponding to the branches of the artery. They then unite to form a single trunk, which
runs up on the medial side of the artery and ends in the corresponding innominate vein. The superior phrenic vein, i.e., the
vein accompanying the pericardiacophrenic artery, usually opens into the internal mammary vein.
The inferior thyroid veins (vv. thyreoideae inferiores) two, frequently three or four, in number, arise in the venous plexus
on the thyroid gland, communicating with the middle and superior thyroid veins. They form a plexus in front of the trachea,
behind the Sternothyreoidei. From this plexus, a left vein descends and joins the left innominate trunk, and a right vein
passes obliquely downward and to the right across the innominate artery to open into the right innominate vein, just at its
junction with the superior vena cava; sometimes the right and left veins open by a common trunk in the latter situation.
These veins receive esophageal tracheal, and inferior laryngeal veins, and are provided with valves at their terminations in
the innominate veins.
The highest intercostal vein (v. intercostalis suprema; superior intercostal veins) (right and left) drain the blood from the
upper three or four intercostal spaces. The right vein (v. intercostalis suprema dextra) passes downward and opens into the
vena azygos; the left vein (v. intercostalis suprema sinistra) runs across the arch of the aorta and the origins of the left subclavian and left common carotid arteries and opens into the left innominate vein. It usually receives the left bronchial vein,
and sometimes the left superior phrenic vein, and communicates below with the accessory hemiazygos vein.
The superior vena cava (v. cava superior) drains the blood from the upper half of the body. It measures about 7 cm. in
length, and is formed by the junction of the two innominate veins. It begins immediately below the cartilage of the right
first rib close to the sternum, and, descending vertically behind the first and second intercostal spaces, ends in the upper
part of the right atrium opposite the upper border of the third right costal cartilage: the lower half of the vessel is within the
pericardium. In its course it describes a slight curve, the convexity of which is to the right side.
Relations. - In front are the anterior margins of the right lung and pleura with the pericardium intervening below; these separate it from the first and second intercostal spaces and from the second and third right costal cartilages; behind it are the
root of the right lung and the right vagus nerve. On its right side are the phrenic nerve and right pleura; on its left side, the
commencement of the innominate artery and the ascending aorta, the latter overlapping it. Just before it pierces the pericar-
dium, it receives the azygos vein and several small veins from the pericardium and other contents of the mediastinal cavity.
The portion contained within the pericardium is covered, in front and laterally, by the serous layer of the membrane. The
superior vena cava has no valves.
The azygos vein (v. azygos; vena azygos major) begins opposite the first or second lumbar vertebra, by a branch, the ascending lumbar vein; sometimes by a branch from the right renal vein, or from the inferior vena cava. It enters the thorax
through the aortic hiatus in the diaphragm, and passes along the right side of the vertebral column to the fourth thoracic
vertebra, where it arches forward over the root of the right lung, and ends in the superior vena cava, just before that vessel
pierces the pericardium. In the aortic hiatus, it lies with the thoracic duct on the right side of the aorta; in the thorax it lies
upon the intercostal arteries, on the right side of the aorta and thoracic duct, and is partly covered by pleura.
Tributaries. - It receives the right subcostal and intercostal veins, the upper three or four of these latter opening by a common stem, the highest superior intercostal vein. It receives the hemiazygos veins, several esophageal, mediastinal, and pericardial veins, and, near its termination, the right bronchial vein. A few imperfect valves are found in the azygos vein; but its
tributaries are provided with complete valves.
The intercostal veins on the left side, below the upper three intercostal spaces, usually form two trunks, named the hemiazygos and accessory hemiazygos veins.
The Hemiazygos Vein (v. hemiazygos; vena azygos minor inferior) begins in the left ascending lumbar or renal vein. It
enters the thorax, through the left crus of the diaphragm, and, ascending on the left side of the vertebral column, as high as
the ninth thoracic vertebra, passes across the column, behind the aorta, esophagus, and thoracic duct, to end in the azygos
vein. It receives the lower four or five intercostal veins and the subcostal vein of the left side, and some esophageal and
mediastinal veins.
The Accessory Hemiazygos Vein (v. hemiazygos accessoria; vena azygos minor superior) descends on the left side of the
vertebral column, and varies inversely in size with the highest left intercostal vein. It receives veins from the three or four
intercostal spaces between the highest left intercostal vein and highest tributary of the hemiazygos; the left bronchial vein
sometimes opens into it. It either crosses the body of the eighth thoracic vertebra to join the azygos vein or ends in the hemiazygos. When this vein is small, or altogether wanting, the left highest intercostal vein may extend as low as the fifth or
sixth intercostal space.
In obstruction of the superior vena cava, the azygos and hemiazygos veins are one of the principal means by which the
venous circulation is carried on, connecting as they do the superior and inferior venae cavae, and communicating with the
common iliac veins by the ascending lumbar veins and with many of the tributaries of the inferior vena cava.
The Bronchial Veins (vv. bronchiales) return the blood from the larger bronchi, and from the structures at the roots of the
lungs; that of the right side opens into the azygos vein, near its termination; that of the left side, into the highest left intercostal or the accessory hemiazygos vein. A considerable quantity of the blood which is carried to the lungs through the
bronchial arteries is returned to the left side of the heart through the pulmonary veins.
The Veins of the Vertebral Column
The veins which drain the blood from the vertebral column, the neighboring muscles, and the meninges of the medulla
spinalis form intricate plexuses extending along the entire length of the column; these plexuses may be divided into two
groups, external and internal, according to their positions inside or outside the vertebral canal. The plexuses of the two
groups anastomose freely with each other and end in the intervertebral veins.
The external vertebral venous plexuses (plexus venosi vertebrales externi; extraspinal veins) best marked in the cervical
region, consist of anterior and posterior plexuses which anastomose freely with each other. The anterior external plexuses
lie in front of the bodies of the vertebrae, communicate with the basivertebral and intervertebral veins, and receive tributaries from the vertebral bodies. The posterior external plexuses are placed partly on the posterior surfaces of the vertebral
arches and their processes, and partly between the deep dorsal muscles. They are best developed in the cervical region, and
there anastomose with the vertebral, occipital, and deep cervical veins.
The internal vertebral venous plexuses (plexus venosi vertebrales interni; intraspinal veins) lie within the vertebral canal
between the dura mater and the vertebrae, and receive tributaries from the bones and from the medulla spinalis. They form
a closer net-work than the external plexuses, and, running mainly in a vertical direction, form four longitudinal veins, two
in front and two behind; they therefore may be divided into anterior and posterior groups. The anterior internal plexuses
consist of large veins which lie on the posterior surfaces of the vertebral bodies and intervertebral fibrocartilages on either
side of the posterior longitudinal ligament; under cover of this ligament they are connected by transverse branches into
which the basivertebral veins open. The posterior internal plexuses are placed, one on either side of the middle line in front
of the vertebral arches and ligamenta flava, and anastomose by veins passing through those ligaments with the posterior
external plexuses. The anterior and posterior plexuses communicate freely with one another by a series of venous rings
(retia venosa vertebrarum), one opposite each vertebra. Around the foramen magnum they form an intricate net-work which
opens into the vertebral veins and is connected above with the occipital sinus, the basilar plexus, the condyloid emissary
vein, and the rete canalis hypoglossi.
The basivertebral veins (vv. basivertebrales) emerge from the foramina on the posterior surfaces of the vertebral bodies.
They are contained in large, tortuous channels in the substance of the bones, similar in every respect to those found in the
diploë of the cranial bones. They communicate through small openings on the front and sides of the bodies of the vertebrae
with the anterior external vertebral plexuses, and converge behind to the principal canal, which is sometimes double toward
its posterior part, and open by valved orifices into the transverse branches which unite the anterior internal vertebral plexuses. They become greatly enlarged in advanced age.
The intervertebral veins (vv. intervertebrales) accompany the spinal nerves through the intervertebral foramina; they receive the veins from the medulla spinalis, drain the internal and external vertebral plexuses and end in the vertebral, intercostal, lumbar, and lateral sacral veins, their orifices being provided with valves.
The veins of the medulla spinalis (vv. spinales; veins of the spinal cord) are situated in the pia mater and form a minute,
tortuous, venous plexus. They emerge chiefly from the median fissures of the medulla spinalis and are largest in the lumbar
region. In this plexus there are (1) two median longitudinal veins, one in front of the anterior fissure, and the other behind
the posterior sulcus of the cord, and (2) four lateral longitudinal veins which run behind the nerve roots. They end in the
intervertebral veins. Near the base of the skull they unite, and form two or three small trunks, which communicate with the
vertebral veins, and then end in the inferior cerebellar veins, or in the inferior petrosal sinuses.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 31. Abdominal part of aorta: relations, paried visceral and parietal branches.
The aim: to learn the structure and relations of aorta and its main branches.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The abdominal aorta begins at the aortic hiatus of the diaphragm, in front of the lower border of the body of the last thoracic vertebra, and, descending in front of the vertebral column, ends on the body of the fourth lumbar vertebra, commonly a
little to the left of the middle line, 103 by dividing into the two common iliac arteries. It diminishes rapidly in size, in consequence of the many large branches which it gives off. As it lies upon the bodies of the vertebrae, the curve which it describes is convex forward, the summit of the convexity corresponding to the third lumbar vertebra.
Relations. - The abdominal aorta is covered, anteriorly, by the lesser omentum and stomach, behind which are the branches
of the celiac artery and the celiac plexus; below these, by the lienal vein, the pancreas, the left renal vein, the inferior part
of the duodenum, the mesentery, and aortic plexus. Posteriorly, it is separated from the lumbar vertebrae and intervertebral
fibrocartilages by the anterior longitudinal ligament and left lumbar veins. On the right side it is in relation above with the
azygos vein, cisterna chyli, thoracic duct, and the right crus of the diaphragm - the last separating it from the upper part of
the inferior vena cava, and from the right celiac ganglion; the inferior vena cava is in contact with the aorta below. On the
left side are the left crus of the diaphragm, the left celiac ganglion, the ascending part of the duodenum, and some coils of
the small intestine.
Collateral Circulation. - The collateral circulation would be carried on by the anastomoses between the internal mammary
and the inferior epigastric; by the free communication between the superior and inferior mesenterics, if the ligature were
placed between these vessels; or by the anastomosis between the inferior mesenteric and the internal pudendal, when (as is
more common) the point of ligature is below the origin of the inferior mesenteric; and possibly by the anastomoses of the
lumbar arteries with the branches of the hypogastric.
The branches of the abdominal aorta may be divided into three sets: visceral, parietal, and terminal.
Visceral Branches.
Parietal Branches
Celiac
Inferior Phrenics
Superior Mesenteric
Lumbars
Inferior Mesenteric
Middle Sacral
Middle Suprarenals
Renals
Internal Spermatics
Terminal Branches
Ovarian (in the female).
Common Iliacs
Of the visceral branches, the celiac artery and the superior and inferior mesenteric arteries are unpaired, while the suprarenals, renals, internal spermatics, and ovarian are paired. Of the parietal branches the inferior phrenics and lumbars are
paired; the middle sacral is unpaired. The terminal branches are paired.
The middle suprarenal arteries (aa. suprarenales media; middle capsular arteries; suprarenal arteries) are two small vessels
which arise, one from either side of the aorta, opposite the superior mesenteric artery. They pass lateralward and slightly
upward, over the crura of the diaphragm, to the suprarenal glands, where they anastomose with suprarenal branches of the
inferior phrenic and renal arteries. In the fetus these arteries are of large size.
The renal arteries (aa. renales), are two large trunks, which arise from the side of the aorta, immediately below the superior mesenteric artery. Each is directed across the crus of the diaphragm, so as to form nearly a right angle with the aorta. The
right is longer than the left, on account of the position of the aorta; it passes behind the inferior vena cava, the right renal
vein, the head of the pancreas, and the descending part of the duodenum. The left is somewhat higher than the right; it lies
behind the left renal vein, the body of the pancreas and the lienal vein, and is crossed by the inferior mesenteric vein. Before reaching the hilus of the kidney, each artery divides into four or five branches; the greater number of these lie between
the renal vein and ureter, the vein being in front, the ureter behind, but one or more branches are usually situated behind the
ureter. Each vessel gives off some small inferior suprarenal branches to the suprarenal gland, the ureter, and the surrounding cellular tissue and muscles. One or two accessory renal arteries are frequently found, more especially on the left side
they usually arise from the aorta, and may come off above or below the main artery, the former being the more common
position. Instead of entering the kidney at the hilus, they usually pierce the upper or lower part of the gland.
The internal spermatic arteries (aa. spermaticae internae; spermatic arteries) are distributed to the testes. They are two
slender vessels of considerable length, and arise from the front of the aorta a little below the renal arteries. Each passes
obliquely downward and lateralward behind the peritoneum, resting on the Psoas major, the right spermatic lying in front of
the inferior vena cava and behind the middle colic and ileocolic arteries and the terminal part of the ileum, the left behind
the left colic and sigmoid arteries and the iliac colon. Each crosses obliquely over the ureter and the lower part of the external iliac artery to reach the abdominal inguinal ring, through which it passes, and accompanies the other constituents of the
spermatic cord along the inguinal canal to the scrotum, where it becomes tortuous, and divides into several branches. Two
or three of these accompany the ductus deferens, and supply the epididymis, anastomosing with the artery of the ductus
deferens; others pierce the back part of the tunica albuginea, and supply the substance of the testis. The internal spermatic
artery supplies one or two small branches to the ureter, and in the inguinal canal gives one or two twigs to the Cremaster.
The ovarian arteries (aa. ovaricae) are the corresponding arteries in the female to the internal spermatic in the male. They
supply the ovaries, are shorter than the internal spermatics, and do not pass out of the abdominal cavity. The origin and
course of the first part of each artery are the same as those of the internal spermatic, but on arriving at the upper opening of
the lesser pelvis the ovarian artery passes inward, between the two layers of the ovariopelvic ligament and of the broad ligament of the uterus, to be distributed to the ovary. Small branches are given to the ureter and the uterine tube, and one passes on to the side of the uterus, and unites with the uterine artery. Other offsets are continued on the round ligament of the
uterus, through the inguinal canal, to the integument of the labium majus and groin.
At an early period of fetal life, when the testes or ovaries lie by the side of the vertebral column, below the kidneys, the
internal spermatic or ovarian arteries are short; but with the descent of these organs into the scrotum or lesser pelvis, the
arteries are gradually lengthened.
The inferior phrenic arteries (aa. phrenicae inferiores) are two small vessels, which supply the diaphragm but present
much variety in their origin. They may arise separately from the front of the aorta, immediately above the celiac artery, or
by a common trunk, which may spring either from the aorta or from the celiac artery. Sometimes one is derived from the
aorta, and the other from one of the renal arteries; they rarely arise as separate vessels from the aorta. They diverge from
one another across the crura of the diaphragm, and then run obliquely upward and lateralward upon its under surface. The
left phrenic passes behind the esophagus, and runs forward on the left side of the esophageal hiatus. The right phrenic passes behind the inferior vena cava, and along the right side of the foramen which transmits that vein. Near the back part of the
central tendon each vessel divides into a medial and a lateral branch. The medial branch curves forward, and anastomoses
with its fellow of the opposite side, and with the musculophrenic and pericardiacophrenic arteries. The lateral branch passes
toward the side of the thorax, and anastomoses with the lower intercostal arteries, and with the musculophrenic. The lateral
branch of the right phrenic gives off a few vessels to the inferior vena cava; and the left one, some branches to the esophagus. Each vessel gives off superior suprarenal branches to the suprarenal gland of its own side. The spleen and the liver also
receive a few twigs from the left and right vessels respectively.
The lumbar arteries (aa. lumbales) are in series with the intercostals. They are usually four in number on either side, and
arise from the back of the aorta, opposite the bodies of the upper four lumbar vertebrae. A fifth pair, small in size, is occasionally present: they arise from the middle sacral artery. They run lateralward and backward on the bodies of the lumbar
vertebrae, behind the sympathetic trunk, to the intervals between the adjacent transverse processes, and are then continued
into the abdominal wall. The arteries of the right side pass behind the inferior vena cava, and the upper two on each side
run behind the corresponding crus of the diaphragm. The arteries of both sides pass beneath the tendinous arches which
give origin to the Psoas major, and are then continued behind this muscle and the lumbar plexus. They now cross the Quadratus lumborum, the upper three arteries running behind, the last usually in front of the muscle. At the lateral border of the
Quadratus lumborum they pierce the posterior aponeurosis of the Transversus abdominis and are carried forward between
this muscle and the Obliquus internus. They anastomose with the lower intercostal, the subcostal, the iliolumbar, the deep
iliac circumflex, and the inferior epigastric arteries.
Branches. - In the interval between the adjacent transverse processes each lumbar artery gives off a posterior ramus which
is continued backward between the transverse processes and is distributed to the muscles and skin of the back; it furnishes a
spinal branch which enters the vertebral canal and is distributed in a manner similar to the spinal branches of the posterior
rami of the intercostal arteries. Muscular branches are supplied from each lumbar artery and from its posterior ramus to the
neighboring muscles.
The middle sacral artery (a. sacralis media) is a small vessel, which arises from the back of the aorta, a little above its bifurcation. It descends in the middle line in front of the fourth and fifth lumbar vertebrae, the sacrum and coccyx, and ends
in the glomus coccygeum (coccygeal gland). From it, minute branches are said to pass to the posterior surface of the rectum. On the last lumbar vertebra it anastomoses with the lumbar branch of the iliolumbar artery; in front of the sacrum it
anastomoses with the lateral sacral arteries, and sends offsets into the anterior sacral foramina. It is crossed by the left
common iliac vein, and is accompanied by a pair of venae comitantes; these unite to form a single vessel, which opens into
the left common iliac vein.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 32. Abdominal part of aorta: unparied visceral branches. Their anastomoses.
The aim: to learn the structure and relations of aorta and its main branches.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The celiac artery (a. caeliaca; celiac axis) is a short thick trunk, about 1.25 cm. in length, which arises from the front of the
aorta, just below the aortic hiatus of the diaphragm, and, passing nearly horizontally forward, divides into three large
branches, the left gastric, the hepatic, and the splenic; it occasionally gives off one of the inferior phrenic arteries.
Relations. - The celiac artery is covered by the lesser omentum. On the right side it is in relation with the right celiac ganglion and the caudate process of the liver; on the left side, with the left celiac ganglion and the cardiac end of the stomach.
Below, it is in relation to the upper border of the pancreas, and the lienal vein.
1. The Left Gastric Artery (a. gastrica sinistra; gastric or coronary artery), the smallest of the three branches of the celiac
artery, passes upward and to the left, posterior to the omental bursa, to the cardiac orifice of the stomach. Here it distributes
branches to the esophagus, which anastomose with the aortic esophageal arteries; others supply the cardiac part of the
stomach, anastomosing with branches of the lienal artery. It then runs from left to right, along the lesser curvature of the
stomach to the pylorus, between the layers of the lesser omentum; it gives branches to both surfaces of the stomach and
anastomoses with the right gastric artery.
2. The Hepatic Artery (a. hepatica) in the adult is intermediate in size between the left gastric and lienal; in the fetus, it is
the largest of the three branches of the celiac artery. It is first directed forward and to the right, to the upper margin of the
superior part of the duodenum, forming the lower boundary of the epiploic foramen (foramen of Winslow). It then crosses
the portal vein anteriorly and ascends between the layers of the lesser omentum, and in front of the epiploic foramen, to the
porta hepatis, where it divides into two branches, right and left, which supply the corresponding lobes of the liver, accompanying the ramifications of the portal vein and hepatic ducts. The hepatic artery, in its course along the right border of the
lesser omentum, is in relation with the common bile-duct and portal vein, the duct lying to the right of the artery, and the
vein behind.
Its branches are: Right Gastric. Gastroduodenal Right Gastroepiploic.
Superior Pancreaticoduodenal.
Cystic.
The right gastric artery (a. gastrica dextra; pyloric artery) arises from the hepatic, above the pylorus, descends to the pyloric end of the stomach, and passes from right to left along its lesser curvature, supplying it with branches, and anastomosing
with the left gastric artery.
The gastroduodenal artery (a. gastroduodenalis) is a short but large branch, which descends, near the pylorus, between the
superior part of the duodenum and the neck of the pancreas, and divides at the lower border of the duodenum into two
branches, the right gastroepiploic and the superior pancreaticoduodenal. Previous to its division it gives off two or three
small branches to the pyloric end of the stomach and to the pancreas.
The right gastroepiploic artery (a. gastroepiploica dextra) runs from right to left along the greater curvature of the stomach, between the layers of the greater omentum, anastomosing with the left gastroepiploic branch of the lienal artery. Except at the pylorus where it is in contact with the stomach, it lies about a finger's breadth from the greater curvature. This
vessel gives off numerous branches, some of which ascend to supply both surfaces of the stomach, while others descend to
supply the greater omentum and anastomose with branches of the middle colic.
The superior pancreaticoduodenal artery (a. pancreaticoduodenalis superior) descends between the contiguous margins of
the duodenum and pancreas. It supplies both these organs, and anastomoses with the inferior pancreaticoduodenal branch of
the superior mesenteric artery, and with the pancreatic branches of the lienal artery.
The cystic artery (a. cystica), usually a branch of the right hepatic, passes downward and forward along the neck of the
gall-bladder, and divides into two branches, one of which ramifies on the free surface, the other on the attached surface of
the gall-bladder.
3. The Lienal or Splenic Artery (a. lienalis), the largest branch of the celiac artery, is remarkable for the tortuosity of its
course. It passes horizontally to the left side, behind the stomach and the omental bursa of the peritoneum, and along the
upper border of the pancreas, accompanied by the lienal vein, which lies below it; it crosses in front of the upper part of the
left kidney, and, on arriving near the spleen, divides into branches, some of which enter the hilus of that organ between the
two layers of the phrenicolienal ligament to be distributed to the tissues of the spleen; some are given to the pancreas, while
others pass to the greater curvature of the stomach between the layers of the gastrolienal ligament. Its branches are:
Pancreatic.
Short Gastric.
Left Gastroepiploic.
The pancreatic branches (rami pancreatici) are numerous small vessels derived from the lienal as it runs behind the upper
border of the pancreas, supplying its body and tail. One of these, larger than the rest, is sometimes given off near the tail of
the pancreas; it runs from left to right near the posterior surface of the gland, following the course of the pancreatic duct,
and is called the arteria pancreatica magna. These vessels anastomose with the pancreatic branches of the pancreaticoduodenal and superior mesenteric arteries.
The short gastric arteries (aa. gastricae breves; vasa brevia) consist of from five to seven small branches, which arise from
the end of the lienal artery, and from its terminal divisions. They pass from left to right, between the layers of the gastrolienal ligament, and are distributed to the greater curvature of the stomach, anastomosing with branches of the left gastric
and left gastroepiploic arteries.
The left gastroepiploic artery (a. gastroepiploica sinistra) the largest branch of the lienal, runs from left to right about a
finger’s breadth or more from the greater curvature of the stomach, between the layers of the greater omentum, and anastomoses with the right gastroepiploic. In its course it distributes several ascending branches to both surfaces of the stomach;
others descend to supply the greater omentum and anastomose with branches of the middle colic.
The superior mesenteric artery (a. mesenterica superior) is a large vessel which supplies the whole length of the small intestine, except the superior part of the duodenum; it also supplies the cecum and the ascending part of the colon and about
one-half of the transverse part of the colon. It arises from the front of the aorta, about 1.25 cm. below the celiac artery, and
is crossed at its origin by the lienal vein and the neck of the pancreas. It passes downward and forward, anterior to the processus uncinatus of the head of the pancreas and inferior part of the duodenum, and descends between the layers of the
mesentery to the right iliac fossa, where, considerably diminished in size, it anastomoses with one of its own branches, viz.,
the ileocolic. In its course it crosses in front of the inferior vena cava, the right ureter and Psoas major, and forms an arch,
the convexity of which is directed foward and downward to the left side, the concavity backward and upward to the right. It
is accompanied by the superior mesenteric vein, which lies to its right side, and it is surrounded by the superior mesenteric
plexus of nerves.
Its branches are: Inferior Pancreaticoduodenal.
Ileocolic.
Intestinal.
Right Colic.
Middle Colic.
The Inferior Pancreaticoduodenal Artery (a. pancreaticoduodenalis inferior) is given off from the superior mesenteric or
from its first intestinal branch, opposite the upper border of the inferior part of the duodenum. It courses to the right between the head of the pancreas and duodenum, and then ascends to anastomose with the superior pancreaticoduodenal artery. It distributes branches to the head of the pancreas and to the descending and inferior parts of the duodenum.
The Intestinal Arteries (aa. intestinales; vasa intestini tenuis) arise from the convex side of the superior mesenteric artery.
They are usually from twelve to fifteen in number, and are distributed to the jejunum and ileum. They run nearly parallel
with one another between the layers of the mesentery, each vessel dividing into two branches, which unite with adjacent
branches, forming a series of arches, the convexities of which are directed toward the intestine. From this first set of arches
branches arise, which unite with similar branches from above and below and thus a second series of arches is formed; from
the lower branches of the artery, a third, a fourth, or even a fifth series of arches may be formed, diminishing in size the
nearer they approach the intestine. In the short, upper part of the mesentery only one set of arches exists, but as the depth of
the mesentery increases, second, third, fourth, or even fifth groups are developed. From the terminal arches numerous small
straight vessels arise which encircle the intestine, upon which they are distributed, ramifying between its coats. From the
intestinal arteries small branches are given off to the lymph glands and other structures between the layers of the mesentery.
The Ileocolic Artery (a. ileocolica) is the lowest branch arising from the concavity of the superior mesenteric artery. It
passes downward and to the right behind the peritoneum toward the right iliac fossa, where it divides into a superior and an
inferior branch; the inferior anastomoses with the end of the superior mesenteric artery, the superior with the right colic
artery.
The inferior branch of the ileocolic runs toward the upper border of the ileocolic junction and supplies the following
branches:
(a) colic, which pass upward on the ascending colon; (b) anterior and posterior cecal, which are distributed to the front and
back of the cecum; (c) an appendicular artery, which descends behind the termination of the ileum and enters the mesenteriole of the vermiform process; it runs near the free margin of this mesenteriole and ends in branches which supply the
vermiform process; and (d) ileal, which run upward and to the left on the lower part of the ileum, and anastomose with the
termination of the superior mesenteric.
The Right Colic Artery (a. colica dextra) arises from about the middle of the concavity of the superior mesenteric artery,
or from a stem common to it and the ileocolic. It passes to the right behind the peritoneum, and in front of the right internal
spermatic or ovarian vessels, the right ureter and the Psoas major, toward the middle of the ascending colon; sometimes the
vessel lies at a higher level, and crosses the descending part of the duodenum and the lower end of the right kidney. At the
colon it divides into a descending branch, which anastomoses with the ileocolic, and an ascending branch, which anastomoses with the middle colic. These branches form arches, from the convexity of which vessels are distributed to the ascending
colon.
The Middle Colic Artery (a. colica media) arises from the superior mesenteric just below the pancreas and, passing
downward and forward between the layers of the transverse mesocolon, divides into two branches, right and left; the former
anastomoses with the right colic; the latter with the left colic, a branch of the inferior mesenteric. The arches thus formed
are placed about two fingers’ breadth from the transverse colon, to which they distribute branches.
The inferior mesenteric artery (a. mesenterica inferior) supplies the left half of the transverse part of the colon, the whole
of the descending and iliac parts of the colon, the sigmoid colon, and the greater part of the rectum. It is smaller than the
superior mesenteric, and arises from the aorta, about 3 or 4 cm. above its division into the common iliacs and close to the
lower border of the inferior part of the duodenum. It passes downward posterior to the peritoneum, lying at first anterior to
and then on the left side of the aorta. It crosses the left common iliac artery and is continued into the lesser pelvis under the
name of the superior hemorrhoidal artery, which descends between the two layers of the sigmoid mesocolon and ends on
the upper part of the rectum.
Its branches are: Left Colic.
Sigmoid.
Superior Hemorrhoidal.
The Left Colic Artery (a. colica sinistra) runs to the left behind the peritoneum and in front of the Psoas major, and after a
short, but variable, course divides into an ascending and a descending branch; the stem of the artery or its branches cross
the left ureter and left internal spermatic vessels. The ascending branch crosses in front of the left kidney and ends, between
the two layers of the transverse mesocolon, by anastomosing with the middle colic artery; the descending branch anastomoses with the highest sigmoid artery. From the arches formed by these anastomoses branches are distributed to the descending colon and the left part of the transverse colon.
The Sigmoid Arteries (aa. sigmoideae), two or three in number, run obliquely downward and to the left behind the peritoneum and in front of the Psoas major, ureter, and internal spermatic vessels. Their branches supply the lower part of the
descending colon, the iliac colon, and the sigmoid or pelvic colon; anastomosing above with the left colic, and below with
the superior hemorrhoidal artery.
The Superior Hemorrhoidal Artery (a. haemorrhoidalis superior), the continuation of the inferior mesenteric, descends
into the pelvis between the layers of the mesentery of the sigmoid colon, crossing, in its course, the left common iliac vessels. It divides, opposite the third sacral vertebra, into two branches, which descend one on either side of the rectum, and
about 10 or 12 cm. from the anus break up into several small branches. These pierce the muscular coat of the bowel and run
downward, as straight vessels, placed at regular intervals from each other in the wall of the gut between its muscular and
mucous coats, to the level of the Sphincter ani internus; here they form a series of loops around the lower end of the rectum, and communicate with the middle hemorrhoidal branches of the hypogastric, and with the inferior hemorrhoidal
branches of the internal pudendal.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 33. System of veins of portal vein and inferior vena cava. Venous anastomoses
(cava-cava and porto-cava anastomoses).
The aim: to learn the structure and relations of inferior vena cava system and important venous anastomoses.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
The external iliac vein (v. iliaca externa), the upward continuation of the femoral vein, begins behind the inguinal ligament, and, passing upward along the brim of the lesser pelvis, ends opposite the sacroiliac articulation, by uniting with the
hypogastric vein to form the common iliac vein. On the right side, it lies at first medial to the artery: but, as it passes upward, gradually inclines behind it. On the left side, it lies altogether on the medial side of the artery. It frequently contains
one, sometimes two, valves.
Tributaries. - The external iliac vein receives the inferior epigastric, deep iliac circumflex, and pubic veins.
The Inferior Epigastric Vein (v. epigastrica inferior; deep epigastric vein) is formed by the union of the venae comitantes
of the inferior epigastric artery, which communicate above with the superior epigastric vein; it joins the external iliac about
1.25 cm. above the inguinal ligament.
The Deep Iliac Circumflex Vein (v. circumflexa ilium profunda) is formed by the union of the venae comitantes of the
deep iliac circumflex artery, and joins the external iliac vein about 2 cm. above the inguinal ligament.
The Pubic Vein communicates with the obturator vein in the obturator foramen, and ascends on the back of the pubis to
the external iliac vein.
The hypogastric vein (v. hypogastrica; internal iliac vein) begins near the upper part of the greater sciatic foramen, passes
upward behind and slightly medial to the hypogastric artery and, at the brim of the pelvis, joins with the external iliac to
form the common iliac vein.
Tributaries. - With the exception of the fetal umbilical vein which passes upward and backward from the umbilicus to the
liver, and the iliolumbar vein which usually joins the common iliac vein, the tributaries of the hypogastric vein correspond
with the branches of the hypogastric artery. It receives (a) the gluteal, internal pudendal, and obturator veins, which have
their origins outside the pelvis; (b) the lateral sacral veins, which lie in front of the sacrum; and (c) the middle hemorrhoidal, vesical, uterine, and vaginal veins, which originate in venous plexuses connected with the pelvic viscera.
1. The Superior Gluteal Veins (vv. glutaeae superiores; gluteal veins) are venae comitantes of the superior gluteal artery;
they receive tributaries from the buttock corresponding with the branches of the artery, and enter the pelvis through the
greater sciatic foramen, above the Piriformis, and frequently unite before ending in the hypogastric vein.
2. The Inferior Gluteal Veins (vv. glutaeae inferiores; sciatic veins), or venae comitantes of the inferior gluteal artery,
begin on the upper part of the back of the thigh, where they anastomose with the medial femoral circumflex and first perforating veins. They enter the pelvis through the lower part of the greater sciatic foramen and join to form a single stem
which opens into the lower part of the hypogastric vein.
3. The Internal Pudendal Veins (internal pudic veins) are the venae comitantes of the internal pudendal artery. They begin
in the deep veins of the penis which issue from the corpus cavernosum penis, accompany the internal pudendal artery, and
unite to form a single vessel, which ends in the hypogastric vein. They receive the veins from the urethral bulb, and the
perineal and inferior hemorrhoidal veins. The deep dorsal vein of the penis communicates with the internal pudendal veins,
but ends mainly in the pudendal plexus.
4. The Obturator Vein (v. obturatoria) begins in the upper portion of the adductor region of the thigh and enters the pelvis
through the upper part of the obturator foramen. It runs backward and upward on the lateral wall of the pelvis below the
obturator artery, and then passes between the ureter and the hypogastric artery, to end in the hypogastric vein.
5. The Lateral Sacral Veins (vv. sacrales laterales) accompany the lateral sacral arteries on the anterior surface of the sacrum and end in the hypogastric vein.
6. The Middle Hemorrhoidal Vein (v. haemorrhoidalis media) takes origin in the hemorrhoidal plexus and receives tributaries from the bladder, prostate, and seminal vesicle; it runs lateralward on the pelvic surface of the Levator ani to end in
the hypogastric vein.
The hemorrhoidal plexus (plexus haemorrhoidalis) surrounds the rectum, and communicates in front with the vesical
plexus in the male, and the uterovaginal plexus in the female. It consists of two parts, an internal in the submucosa, and an
external outside the muscular coat. The internal plexus presents a series of dilated pouches which are arranged in a circle
around the tube, immediately above the anal orifice, and are connected by transverse branches.
The lower part of the external plexus is drained by the inferior hemorrhoidal veins into the internal pudendal vein; the
middle part by the middle hemorrhoidal vein which joins the hypogastric vein; and the upper part by the superior hemorrhoidal vein which forms the commencement of the inferior mesenteric vein, a tributary of the portal vein. A free communication between the portal and systemic venous systems is established through the hemorrhoidal plexus.
The veins of the hemorrhoidal plexus are contained in very loose, connective tissue, so that they get less support from
surrounding structures than most other veins, and are less capable of resisting increased blood-pressure.
The pudendal plexus (plexus pudendalis; vesicoprostatic plexus) lies behind the arcuate public ligament and the lower part
of the symphysis pubis, and in front of the bladder and prostate. Its chief tributary is the deep dorsal vein of the penis, but it
also receives branches from the front of the bladder and prostate. It communicates with the vesical plexus and with the internal pudendal vein and drains into the vesical and hypogastric veins. The prostatic veins form a well-marked prostatic
plexus which lies partly in the fascial sheath of the prostate and partly between the sheath and the prostatic capsule. It
communicates with the pudendal and vesical plexuses.
The vesical plexus (plexus vesicalis) envelops the lower part of the bladder and the base of the prostate and communicates
with the pudendal and prostatic plexuses. It is drained, by means of several vesical veins, into the hypogastric veins.
The Dorsal Veins of the Penis (vv. dorsales penis) are two in number, a superficial and a deep. The superficial vein drains
the prepuce and skin of the penis, and, running backward in the subcutaneous tissue, inclines to the right or left, and opens
into the corresponding superficial external pudendal vein, a tributary of the great saphenous vein. The deep vein lies beneath the deep fascia of the penis; it receives the blood from the glans penis and corpora cavernosa penis and courses
backward in the middle line between the dorsal arteries; near the root of the penis it passes between the two parts of the
suspensory ligament and then through an aperture between the arcuate pubic ligament and the transverse ligament of the
pelvis, and divides into two branches, which enter the pudendal plexus. The deep vein also communicates below the symphysis pubis with the internal pudendal vein.
The uterine plexuses lie along the sides and superior angles of the uterus between the two layers of the broad ligament,
and communicate with the ovarian and vaginal plexuses. They are drained by a pair of uterine veins on either side: these
arise from the lower part of the plexuses, opposite the external orifice of the uterus, and open into the corresponding hypogastric vein.
The vaginal plexuses are placed at the sides of the vagina; they communicate with the uterine, vesical, and hemorrhoidal
plexuses, and are drained by the vaginal veins, one on either side, into the hypogastric veins.
The common iliac veins (vv. iliacae communes) are formed by the union of the external iliac and hypogastric veins, in
front of the sacroiliac articulation; passing obliquely upward toward the right side, they end upon the fifth lumbar vertebra,
by uniting with each other at an acute angle to form the inferior vena cava. The right common iliac is shorter than the left,
nearly vertical in its direction, and ascends behind and then lateral to its corresponding artery. The left common iliac, longer than the right and more oblique in its course, is at first situated on the medial side of the corresponding artery, and then
behind the right common iliac. Each common iliac receives the iliolumbar, and sometimes the lateral sacral veins. The left
receives, in addition, the middle sacral vein. No valves are found in these veins.
The Middle Sacral Veins (vv. sacrales mediales) accompany the corresponding artery along the front of the sacrum, and
join to form a single vein, which ends in the left common iliac vein; sometimes in the angle of junction of the two iliac
veins.
Peculiarities. - The left common iliac vein, instead of joining with the right in its usual position, occasionally ascends on
the left side of the aorta as high as the kidney, where, after receiving the left renal vein, it crosses over the aorta, and then
joins with the right vein to form the vena cava. In these cases, the two common iliacs are connected by a small communicating branch at the spot where they are usually united.
The inferior vena cava (v. cava inferior), returns to the heart the blood from the parts below the diaphragm. It is formed by
the junction of the two common iliac veins, on the right side of the fifth lumbar vertebra. It ascends along the front of the
vertebral column, on the right side of the aorta, and, having reached the liver, is continued in a groove on its posterior surface. It then perforates the diaphragm between the median and right portions of its central tendon; it subsequently inclines
forward and medialward for about 2.5 cm., and, piercing the fibrous pericardium, passes behind the serous pericardium to
open into the lower and back part of the right atrium. In front of its atrial orifice is a semilunar valve, termed the valve of
the inferior vena cava: this is rudimentary in the adult, but is of large size and exercises an important function in the fetus.
Relations. - The abdominal portion of the inferior vena cava is in relation in front, from below upward, with the right common iliac artery, the mesentery, the right internal spermatic artery, the inferior part of the duodenum, the pancreas, the
common bile duct, the portal vein, and the posterior surface of the liver; the last partly overlaps and occasionally completely surrounds it; behind, with the vertebral column, the right Psoas major, the right crus of the diaphragm, the right inferior
phrenic, suprarenal, renal and lumbar arteries, right sympathetic trunk and right celiac ganglion, and the medial part of the
right suprarenal gland; on the right side, with the right kidney and ureter; on the left side, with the aorta, right crus of the
diaphragm, and the caudate lobe of the liver.
The thoracic portion is only about 2.5 cm. in length, and is situated partly inside and partly outside the pericardial sac. The
extrapericardial part is separated from the right pleura and lung by a fibrous band, named the right phrenicopericardiac ligament. This ligament, often feebly marked, is attached below to the margin of the vena-caval opening in the diaphragm,
and above to the pericardium in front of and behind the root of the right lung. The intrapericardiac part is very short, and is
covered antero-laterally by the serous layer of the pericardium.
Peculiarities. - In Position. - This vessel is sometimes placed on the left side of the aorta, as high as the left renal vein, and,
after receiving this vein, crosses over to its usual position on the right side; or it may be placed altogether on the left side of
the aorta, and in such a case the abdominal and thoracic viscera, together with the great vessels, are all transposed.
Point of Termination. - Occasionally the inferior vena cava joins the azygos vein, which is then of large size. In such cases, the superior vena cava receives the whole of the blood from the body before transmitting it to the right atrium, except
the blood from the hepatic veins, which passes directly into the right atrium.
Tributaries. - The inferior vena cava receives the following veins:
Lumbar.
Renal. Inferior Phrenic.
Right Spermatic or Ovarian.
Suprarenal.
Hepatic.
The Lumbar Veins (vv. lumbales) four in number on each side, collect the blood by dorsal tributaries from the muscles
and integument of the loins, and by abdominal tributaries from the walls of the abdomen, where they communicate with the
epigastric veins. At the vertebral column, they receive veins from the vertebral plexuses, and then pass forward, around the
sides of the bodies of the vertebrae, beneath the Psoas major, and end in the back part of the inferior cava. The left lumbar
veins are longer than the right, and pass behind the aorta. The lumbar veins are connected together by a longitudinal vein
which passes in front of the transverse processes of the lumbar vertebrae, and is called the ascending lumbar; it forms the
most frequent origin of the corresponding azygos or hemiazygos vein, and serves to connect the common iliac, iliolumbar,
and azygos or hemiazygos veins of its own side of the body.
The Spermatic Veins (vv. spermaticae) emerge from the back of the testis, and receive tributaries from the epididymis;
they unite and form a convoluted plexus, called the pampiniform plexus, which constitutes the greater mass of the spermatic cord; the vessels composing this plexus are very numerous, and ascend along the cord, in front of the ductus deferens.
Below the subcutaneous inguinal ring they unite to form three or four veins, which pass along the inguinal canal, and, entering the abdomen through the abdominal inguinal ring, coalesce to form two veins, which ascend on the Psoas major,
behind the peritoneum, lying one on either side of the internal spermatic artery. These unite to form a single vein, which
opens on the right side into the inferior vena cava, at an acute angle; on the left side into the left renal vein, at a right angle.
The spermatic veins are provided with valves. The left spermatic vein passes behind the iliac colon, and is thus exposed to
pressure from the contents of that part of the bowel.
The Ovarian Veins (vv. ovaricae) correspond with the spermatic in the male; they form a plexus in the broad ligament
near the ovary and uterine tube, and communicate with the uterine plexus. They end in the same way as the spermatic veins
in the male. Valves are occasionally found in these veins. Like the uterine veins, they become much enlarged during pregnancy.
The Renal Veins (vv. renales) are of large size, and placed in front of the renal arteries. The left is longer than the right,
and passes in front of the aorta, just below the origin of the superior mesenteric artery. It receives the left spermatic and left
inferior phrenic veins, and, generally, the left suprarenal vein. It opens into the inferior vena cava at a slightly higher level
than the right.
The Suprarenal Veins (vv. suprarenales) are two in number: the right ends in the inferior vena cava; the left, in the left
renal or left inferior phrenic vein.
The Inferior Phrenic Veins (vv. phrenicae inferiores) follow the course of the inferior phrenic arteris; the right ends in the
inferior vena cava; the left is often represented by two branches, one of which ends in the left renal or suprarenal vein,
while the other passes in front of the esophageal hiatus in the diaphragm and opens into the inferior vena cava.
The Hepatic Veins (vv. hepaticae) commence in the substance of the liver, in the terminations of the portal vein and hepatic artery, and are arranged in two groups, upper and lower. The upper group usually consists of three large veins, which
converge toward the posterior surface of the liver, and open into the inferior vena cava, while that vessel is situated in the
groove on the back part of the liver. The veins of the lower group vary in number, and are of small size; they come from the
right and caudate lobes. The hepatic veins run singly, and are in direct contact with the hepatic tissue. They are destitute of
valves.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 34. General lymphology. Anatomic characteristic of lymphatic capillaries, vessels,
collectors. Lymphatic nodes. Special lymphology. Regional lymphatic nodes and vessels.
The aim: to learn the structure and relations of main lymphatic collectors, groups of lymphatic nodes and
the routes of lymphatic drainage from extremities and internal organs.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
THE LYMPHATIC SYSTEM consists (1) of complex capillary networks which collect the lymph in the various organs
and tissues; (2) of an elaborate system of collecting vessels which conduct the lymph from the capillaries to the large veins
of the neck at the junction of the internal jugular and subclavian veins, where the lymph is poured into the blood stream;
and (3) lymph glands or nodes which are interspaced in the pathways of the collecting vessels filtering the lymph as it passes through them and contributing lymphocytes to it. The lymphatic capillaries and collecting vessels are lined throughout
by a continuous layer of endothelial cells, forming thus a closed system. The lymphatic vessels of the small intestine receive the special designation of lacteals or chyliferous vessels; they differ in no respect from the lymphatic vessels generally excepting that during the process of digestion they contain a milk-white fluid, the chyle.
The Development of the Lymphatic Vessels. - The lymphatic system begins as a series of sacs at the points of junction of
certain of the embryonic veins. These lymph-sacs are developed by the confluence of numerous venous capillaries, which
at first lose their connections with the venous system, but subsequently, on the formation of the sacs, regain them. The
lymphatic system is therefore developmentally an offshoot of the venous system, and the lining walls of its vessels are always endothelial.
In the human embryo the lymph sacs from which the lymphatic vessels are derived are six in number; two paired, the jugular and the posterior lymph-sacs; and two unpaired, the retroperitoneal and the cisterna chyli. In lower mammals an additional pair, subclavian, is present, but in the human embryo these are merely extensions of the jugular sacs.
The position of the sacs is as follows: (1) jugular sac, the first to appear, at the junction of the subclavian vein with the
primitive jugular; (2) posterior sac, at the junction of the iliac vein with the cardinal; (3) retroperitoneal, in the root of the
mesentery near the suprarenal glands; (4) cisterna chyli, opposite the third and fourth lumbar vertebrae. From the lymphsacs the lymphatic vessels bud out along fixed lines corresponding more or less closely to the course of the embryonic
bloodvessels. Both in the body-wall and in the wall of the intestine, the deeper plexuses are the first to be developed; by
continued growth of these the vessels in the superficial layers are gradually formed. The thoracic duct is probably formed
from anastomosing outgrowths from the jugular sac and cisterna chyli. At its connection with the cisterna chyli it is at first
double, but the two vessels soon join.
All the lymph-sacs except the cisterna chyli are, at a later stage, divided up by slender connective tissue bridges and transformed into groups of lymph glands. The lower portion of the cisterna chyli is similarly converted, but its upper portion
remains as the adult cisterna.
Lymphatic Capillaries. - The complex capillary plexuses which consist of a single layer of thin flat endothelial cells lie in
the connective-tissue spaces in the various regions of the body to which they are distributed and are bathed by the intercellular tissue fluids. Two views are at present held as to the mode in which the lymph is formed: one being by the physical
processes of filtration, diffusion, and osmosis, and the other, that in addition to these physical processes the endothelial
cells have an active secretory function. The colorless liquid lymph has about the same composition as the blood plasma. It
contains many lymphocytes and frequently red blood corpuscles. Granules and bacteria are also taken up by the lymph
from the connective-tissue spaces, partly by the action of lymphocytes which pass into the lymph between the endothelial
cells and partly by the direct passage of the granules through the endothelial cells.
The lymphatic capillary plexuses vary greatly in form; the anastomoses are usually numerous; blind ends or cul-de-sacs
are especially common in the intestinal villi, the dermal papillae and the filiform papillae of the tongue. The plexuses are
often in two layers: a superficial and a deep, the superficial being of smaller caliber than the deep. The caliber, however,
varies greatly in a given plexus from a few micromillimeters to one millimeter. The capillaries are without valves.
Distribution. - The Skin. - Lymphatic capillaries are abundant in the dermis where they form superficial and deep plexuses,
the former sending blind ends into the dermal papillae. The plexuses are especially rich over the palmar surface of the
hands and fingers and over the plantar surface of the feet and toes. The epidermis is without capillaries. The conjunctiva
has an especially rich plexus.
The subcutaneous tissue is without capillaries.
The tendons of striated muscle and muscle sheaths are richly supplied. In muscle, however, their existence is still disputed.
The periosteum of bone is richly supplied and they have been described in the Haversian canals. They are absent in cartilage and probably in bone marrow.
The joint capsules are richly supplied with lymphatic capillaries, they do not, however, open into the joint cavities.
Beneath the mesothelium lining of the pleural, peritoneal and pericardial cavities are rich plexuses; they do not open into
these cavities.
The alimentary canal is supplied with rich plexuses beneath the epithelium, often as a superficial plexus in the mucosa and
a deeper submucosal plexus. Cul-de-sacs extend into the filiform papillae of the tongue and the villi of the small intestine.
Those portions of the alimentary canal covered by peritoneum, have in addition a subserous lymphatic capillary plexus beneath the mesothelium.
The salivary glands are supplied with lymphatic capillaries.
The liver has a rich subserous plexus in the capsule and also extensive plexuses which accompany the hepatic artery and
portal vein. The lymphatic capillaries have not been followed into the liver lobules. The lymph from the liver forms a large
part of that which flows through the thoracic duct. The gall-bladder and bile ducts have rich subepithelial plexuses and the
former a subserous plexus.
The spleen has a rich subserous set and a capsular set of lymphatic capillaries. Their presence in the parenchyma is uncertain.
The nasal cavity has extensive capillary plexuses in the mucosa and submucosa.
The trachea and bronchi have plexuses in the mucosa and submucosa but the smaller bronchi have only a single layer. The
capillaries do not extend to the air-cells. The plexuses around the smaller bronchi connect with the rich subserous plexus of
the lungs in places where the veins reach the surface.
Lymphatics have been described in the thyroid gland and in the thymus.
The adrenal has a superficial plexus divided into two layers, one in the loose tissue about the gland and the other beneath
the capsule. Capillaries have also been described within the parenchyma.
The kidney is supplied with a coarse subserous plexus and a deeper plexus of finer capillaries in the capsule. Lymphatics
have been described within the substance of the kidney surrounding the tubules.
The urinary bladder has a rich plexus of lymphatic capillaries just beneath the epithelial lining, also a subserous set which
anastomoses with the former through the muscle layer. The submucous plexus is continuous with the submucous plexus of
the urethra.
The prostate has a rich lymphatic plexus surrounding the gland and a wide-meshed subcapsular plexus.
The testis has a rich superficial plexus beneath the tunica albuginea. The presence of deep lymphatics is disputed.
The uterus is provided with a subserous plexus, the deeper lymphatics are uncertain. Subepithelial plexuses are found in
the vagina.
The ovary has a rich superficial plexus and a deep interstitial plexus.
The heart has a rich subserous plexus beneath the epicardium. Lymphatic capillaries have also been described beneath the
endocardium and throughout the muscle.
Lymphatic capillaries are probably absent in the central nervous system, the meninges, the eyeball (except the conjunctiva), the orbit, the internal ear, within striated muscle, the liver lobule, the spleen pulp and kidney parenchyma. They are
entirely absent in cartilage. In many places further investigation is needed.
Lymphatic Vessels. - The lymphatic vessels are exceedingly delicate, and their coats are so transparent that the fluid they
contain is readily seen through them. They are interrupted at intervals by constrictions, which give them a knotted or beaded appearance; these constrictions correspond to the situations of valves in their interior. Lymphatic vessels have been
found in nearly every texture and organ of the body which contains bloodvessels. Such non-vascular structures as cartilage,
the nails, cuticle, and hair have none, but with these exceptions it is probable that eventually all parts will be found to be
permeated by these vessels.
Structure of Lymphatic Vessels. - The larger lymphatic vessels are each composed of three coats. The internal coat is thin,
transparent, slightly elastic, and consists of a layer of elongated endothelial cells with wavy margins by which the contiguous cells are dovetailed into one another; the cells are supported on an elastic membrane. The middle coat is composed of
smooth muscular and fine elastic fibers, disposed in a transverse direction. The external coat consists of connective tissue,
intermixed with smooth muscular fibers longitudinally or obliquely disposed; it forms a protective covering to the other
coats, and serves to connect the vessel with the neighboring structures. In the smaller vessels there are no muscular or elas-
tic fibers, and the wall consists only of a connective-tissue coat, lined by endothelium. The thoracic duct has a more complex structure than the other lymphatic vessels; it presents a distinct subendothelial layer of branched corpuscles, similar to
that found in the arteries; in the middle coat there is, in addition to the muscular and elastic fibers, a layer of connective
tissue with its fibers arranged longitudinally. The lymphatic vessels are supplied by nutrient vessels, which are distributed
to their outer and middle coats; and here also have been traced many non-medullated nerves in the form of a fine plexus of
fibrils.
The valves of the lymphatic vessels are formed of thin layers of fibrous tissue covered on both surfaces by endothelium
which presents the same arrangement as on the valves of veins. In form the valves are semilunar; they are attached by their
convex edges to the wall of the vessel, the concave edges being free and directed along the course of the contained current.
Usually two such valves, of equal size, are found opposite one another; but occasionally exceptions occur, especially at or
near the anastomoses of lymphatic vessels. Thus, one valve may be of small size and the other increased in proportion.
In the lymphatic vessels the valves are placed at much shorter intervals than in the veins. They are most numerous near the
lymph glands, and are found more frequently in the lymphatic vessels of the neck and upper extremity than in those of the
lower extremity. The wall of the lymphatic vessel immediately above the point of attachment of each segment of a valve is
expanded into a pouch or sinus which gives to these vessels, when distended, the knotted or beaded appearance already
referred to. Valves are wanting in the vessels composing the plexiform net-work in which the lymphatic vessels usually
originate on the surface of the body.
Lymph Glands (lymphoglandulae). - The lymph glands are small oval or bean-shaped bodies, situated in the course of lymphatic and lacteal vessels so that the lymph and chyle pass through them on their way to the blood. Each generally presents
on one side a slight depression - the hilus - through which the bloodvessels enter and leave the interior. The efferent lymphatic vessel also emerges from the gland at this spot, while the afferent vessels enter the organ at different parts of the
periphery. On section a lymph gland displays two different structures: an external, of lighter color - the cortical; and an
internal, darker - the medullary. The cortical structure does not form a complete investment, but is deficient at the hilus,
where the medullary portion reaches the surface of the gland; so that the efferent vessel is derived directly from the medullary structures, while the afferent vessels empty themselves into the cortical substance.
Structure of Lymph Glands. - A lymph gland consists of (1) a fibrous envelope, or capsule, from which a frame-work of
processes (trabeculae) proceeds inward, imperfectly dividing the gland into open spaces freely communicating with each
other; (2) a quantity of lymphoid tissue occupying these spaces without completely filling them; (3) a free supply of
bloodvessels, which are supported in the trabeculae; and (4) the afferent and efferent vessels communicating through the
lymph paths in the substance of the gland. The nerves passing into the hilus are few in number and are chiefly distributed to
the bloodvessels supplying the gland
The capsule is composed of connective tissue with some plain muscle fibers, and from its internal surface are given off a
number of membranous processes or trabeculae, consisting, in man, of connective tissue, with a small admixture of plain
muscle fibers; but in many of the lower animals composed almost entirely of involuntary muscle. They pass inward, radiating toward the center of the gland, for a certain distance - that is to say, for about one-third or one-fourth of the space between the circumference and the center of the gland. In some animals they are sufficiently well-marked to divide the peripheral or cortical portion of the gland into a number of compartments (so-called follicles), but in man this arrangement is
not obvious. The larger trabeculae springing from the capsule break up into finer bands, and these interlace to form a meshwork in the central or medullary portion of the gland. In these spaces formed by the interlacing trabeculae is contained the
proper gland substance or lymphoid tissue. The gland pulp does not, however, completely fill the spaces, but leaves, between its outer margin and the enclosing trabeculae, a channel or space of uniform width throughout. This is termed the
lymph path or lymph sinus. Running across it are a number of finer trabeculae of retiform connective tissue, the fibers of
which are, for the most part, covered by ramifying cells.
On account of the peculiar arrangement of the frame-work of the organ, the gland pulp in the cortical portion is disposed
in the form of nodules, and in the medullary part in the form of rounded cords. It consists of ordinary lymphoid tissue, being made up of a delicate net-work of retiform tissue, which is continuous with that in the lymph paths, but marked off
from it by a closer reticulation; it is probable, moreover, that the reticular tissue of the gland pulp and the lymph paths is
continuous with that of the trabeculae, and ultimately with that of the capsule of the gland. In its meshes, in the nodules and
cords of lymphoid tissue, are closely packed lymph corpuscles. The gland pulp is traversed by a dense plexus of capillary
bloodvessels. The nodules or follicles in the cortical portion of the gland frequently show, in their centers, areas where karyokinetic figures indicate a division of the lymph corpuscles. These areas are termed germ centers. The cells composing
them have more abundant protoplasm than the peripheral cells.
The afferent vessels, as stated above, enter at all parts of the periphery of the gland, and after branching and forming a
dense plexus in the substance of the capsule, open into the lymph sinuses of the cortical part. In doing this they lose all their
coats except their endothelial lining, which is continuous with a layer of similar cells lining the lymph paths. In like manner
the efferent vessel commences from the lymph sinuses of the medullary portion. The stream of lymph carried to the gland
by the afferent vessels thus passes through the plexus in the capsule to the lymph paths of the cortical portion, where it is
exposed to the action of the gland pulp; flowing through these it enters the paths or sinuses of the medullary portion, and
finally emerges from the hilus by means of the efferent vessel. The stream of lymph in its passage through the lymph sinuses is much retarded by the presence of the reticulum, hence morphological elements, either normal or morbid, are easily
arrested and deposited in the sinuses. Many lymph corpuscles pass with the efferent lymph stream to join the general blood
stream. The arteries of the gland enter at the hilus, and either go at once to the gland pulp, to break up into a capillary plexus, or else run along the trabeculae, partly to supply them and partly running across the lymph paths, to assist in forming
the capillary plexus of the gland pulp. This plexus traverses the lymphoid tissue, but does not enter into the lymph sinuses.
From it the veins commence and emerge from the organ at the same place as that at which the arteries enter.
The lymphatic vessels are arranged into a superficial and a deep set. On the surface of the body the superficial lymphatic
vessels are placed immediately beneath the integument, accompanying the superficial veins; they join the deep lymphatic
vessels in certain situations by perforating the deep fascia. In the interior of the body they lie in the submucous areolar tissue, throughout the whole length of the digestive, respiratory, and genito-urinary tracts; and in the subserous tissue of the
thoracic and abdominal walls. Plexiform networks of minute lymphatic vessels are found interspersed among the proper
elements and bloodvessels of the several tissues; the vessels composing the net-work, as well as the meshes between them,
are much larger than those of the capillary plexus. From these net-works small vessels emerge, which pass, either to a
neighboring gland, or to join some larger lymphatic trunk. The deep lymphatic vessels, fewer in number, but larger than the
superficial, accompany the deep bloodvessels. Their mode of origin is probably similar to that of the superficial vessels.
The lymphatic vessels of any part or organ exceed the veins in number, but in size they are much smaller. Their anastomoses also, especially those of the large trunks, are more frequent, and are effected by vessels equal in diameter to those which
they connect, the continuous trunks retaining the same diameter.
Lymph. - Lymph, found only in the closed lymphatic vessels, is a transparent, colorless, or slightly yellow, watery fluid of
specific gravity about 1.015; it closely resembles the blood plasma, but is more dilute. When it is examined under the microscope, leucocytes of the lymphocyte class are found floating in the transparent fluid; they are always increased in number after the passage of the lymph through lymphoid tissue, as in lymph glands. Lymph should be distinguished from “tissue fluid” 109 which is found outside the lymphatic vessels in the tissue spaces.
The thoracic duct (ductus thoracicus) conveys the greater part of the lymph and chyle into the blood. It is the common trunk
of all the lymphatic vessels of the body, excepting those on the right side of the head, neck, and thorax, and right upper
extremity, the right lung, right side of the heart, and the convex surface of the liver. In the adult it varies in length from 38
to 45 cm. and extends from the second lumbar vertebra to the root of the neck. It begins in the abdomen by a triangular dilatation, the cisterna chyli, which is situated on the front of the body of the second lumbar vertebra, to the right side of and
behind the aorta, by the side of the right crus of the diaphragm. It enters the thorax through the aortic hiatus of the diaphragm, and ascends through the posterior mediastinal cavity between the aorta and azygos vein. Behind it in this region
are the vertebral column, the right intercostal arteries, and the hemiazygos veins as they cross to open into the azygos vein;
in front of it are the diaphragm, esophagus, and pericardium, the last being separated from it by a recess of the right pleural
cavity. Opposite the fifth thoracic vertebra, it inclines toward the left side, enters the superior mediastinal cavity, and ascends behind the aortic arch and the thoracic part of the left subclavian artery and between the left side of the esophagus
and the left pleura, to the upper orifice of the thorax. Passing into the neck it forms an arch which rises about 3 or 4 cm.
above the clavicle and crosses anterior to the subclavian artery, the vertebral artery and vein, and the thyrocervical trunk or
its branches. It also passes in front of the phrenic nerve and the medial border of the Scalenus anterior, but is separated
from these two structures by the prevertebral fascia. In front of it are the left common carotid artery, vagus nerve, and internal jugular vein; it ends by opening into the angle of junction of the left subclavian vein with the left internal jugular
vein. The thoracic duct, at its commencement, is about equal in diameter to a goose-quill, but it diminishes considerably in
caliber in the middle of the thorax, and is again dilated just before its termination. It is generally flexuous, and constricted
at intervals so as to present a varicose appearance. Not infrequently it divides in the middle of its course into two vessels of
unequal size which soon reunite, or into several branches which form a plexiform interlacement. It occasionally divides at
its upper part into two branches, right and left; the left ending in the usual manner, while the right opens into the right subclavian vein, in connection with the right lymphatic duct. The thoracic duct has several valves; at its termination it is provided with a pair, the free borders of which are turned toward the vein, so as to prevent the passage of venous blood into the
duct.
The cisterna chyli (receptaculum chyli) receives the two lumbar lymphatic trunks, right and left, and the intestinal lymphatic trunk. The lumbar trunks are formed by the union of the efferent vessels from the lateral aortic lymph glands. They
receive the lymph from the lower limbs, from the walls and viscera of the pelvis, from the kidneys and suprarenal glands
and the deep lymphatics of the greater part of the abdominal wall. The intestinal trunk receives the lymph from the stomach
and intestine, from the pancreas and spleen, and from the lower and front part of the liver.
Tributaries. - Opening into the commencement of the thoracic duct, on either side, is a descending trunk from the posterior
intercostal lymph glands of the lower six or seven intercostal spaces. In the thorax the duct is joined, on either side, by a
trunk which drains the upper lumbar lymph glands and pierces the crus of the diaphragm. It also receives the efferents from
the posterior mediastinal lymph glands and from the posterior intercostal lymph glands of the upper six left spaces. In the
neck it is joined by the left jugular and left subclavian trunks, and sometimes by the left bronchomediastinal trunk; the lastnamed, however, usually opens independently into the junction of the left subclavian and internal jugular veins.
The right lymphatic duct (ductus lymphaticus dexter), about 1.25 cm. in length, courses along the medial border of the
Scalenus anterior at the root of the neck and ends in the right subclavian vein, at its angle of junction with the right internal
jugular vein. Its orifice is guarded by two semilunar valves, which prevent the passage of venous blood into the duct.
Tributaries. - The right lymphatic duct receives the lymph from the right side of the head and neck through the right jugular
trunk; from the right upper extremity through the right subclavian trunk; from the right side of the thorax, right lung, right
side of the heart, and part of the convex surface of the liver, through the right bronchomediastinal trunk. These three collecting trunks frequently open separately in the angle of union of the two veins.
The Lymph Glands of the Head.
The lymph glands of the head are arranged in the following groups:
Occipital.
Facial.
Posterior Auricular.
Parotid.
Retropharyngeal.
Deep Facial.
Anterior Auricular.
Lingual.
The occipital glands (lymphoglandulae occipitales), one to three in nu ber, are placed on the back of the head close to the
margin of the Trapezius and resting on the insertion of the Semispinalis capitis. Their afferent vessels drain the occipital
region of the scalp, while their efferents pass to the superior deep cervical glands.
The posterior auricular glands (lymphoglandulae auriculares; mastoid glands), usually two in number, are situated on the
mastoid insertion of the Sternocleidomastoideus, beneath the Auricularis posterior. Their afferent vessels drain the posterior
part of the temporoparietal region, the upper part of the cranial surface of the auricula or pinna, and the back of the external
acoustic meatus; their efferents pass to the superior deep cervical glands.
The anterior auricular glands (lymphoglandulae auriculares anteriores; superficial parotid or preauricular glands), from
one to three in number, lie immediately in front of the tragus. Their afferents drain the lateral surface of the auricula and the
skin of the adjacent part of the temporal region; their efferents pass to the superior deep cervical glands.
The parotid glands (lymphoglandulae parotideae), form two groups in relation with the parotid salivary gland, viz., a
group imbedded in the substance of the gland, and a group of subparotid glands lying on the lateral wall of the pharynx.
Occasionally small glands are found in the subcutaneous tissue over the parotid gland. Their afferent vessels drain the root
of the nose, the eyelids, the frontotemporal region, the external acoustic meatus and the tympanic cavity, possibly also the
posterior parts of the palate and the floor of the nasal cavity. The efferents of these glands pass to the superior deep cervical
glands. The afferents of the subparotid glands drain the nasal part of the pharynx and the posterior parts of the nasal cavities; their efferents pass to the superior deep cervical glands.
The facial glands comprise three groups: (a) infraorbital or maxillary, scattered over the infraorbital region from the
groove between the nose and cheek to the zygomatic arch; (b) buccinator, one or more placed on the Buccinator opposite
the angle of the mouth; (c) supramandibular, on the outer surface of the mandible, in front of the Masseter and in contact
with the external maxillary artery and anterior facial vein. Their efferent vessels drain the eyelids, the conjunctiva, and the
skin and mucous membrane of the nose and cheek; their efferents pass to the submaxillary glands.
The deep facial glands (lymphoglandulae faciales profunda; internal maxillary glands) are placed beneath the ramus of the
mandible, on the outer surface of the Pterygoideus externus, in relation to the internal maxillary artery. Their afferent vessels drain the temporal and infratemporal fossae and the nasal part of the pharynx their efferents pass to the superior deep
cervical glands.
The lingual glands (lymphoglandulae linguales) are two or three small nodules lying on the Hyoglossus and under the
Genioglossus. They form merely glandular substations in the course of the lymphatic vessels of the tongue.
The retropharyngeal glands, from one to three in number, lie in the buccopharyngeal fascia, behind the upper part of the
pharynx and in front of the arch of the atlas, being separated, however, from the latter by the Longus capitis. Their afferents
drain the nasal cavities, the nasal part of the pharynx, and the auditory tubes; their efferents pass to the superior deep cervical glands.
The lymphatic vessels of the scalp are divisible into (a) those of the frontal region, which terminate in the anterior auricular and parotid glands; (b) those of the temporoparietal region, which end in the parotid and posterior auricular glands; and
(c) those of the occipital region, which terminate partly in the occipital glands and partly in a trunk which runs down along
the posterior border of the Sternocleidomastoideus to end in the inferior deep cervical glands.
The lymphatic vessels of the auricula and external acoustic meatus are also divisible into three groups: (a) an anterior,
from the lateral surface of the auricula and anterior wall of the meatus to the anterior auricular glands; (b) a posterior, from
the margin of the auricula, the upper part of its cranial surface, the internal surface and posterior wall of the meatus to the
posterior auricular and superior deep cervical glands; (c) an inferior, from the floor of the meatus and from the lobule of the
auricula to the superficial and superior deep cervical glands.
The lymphatic vessels of the face are more numerous than those of the scalp. Those from the eyelids and conjunctiva terminate partly in the submaxillary but mainly in the parotid glands. The vessels from the posterior part of the cheek also
pass to the parotid glands, while those from the anterior portion of the cheek, the side of the nose, the upper lip, and the
lateral portions of the lower lip end in the submaxillary glands. The deeper vessels from the temporal and infratemporal
fossae pass to the deep facial and superior deep cervical glands. The deeper vessels of the cheek and lips end, like the superficial, in the submaxillary glands. Both superficial and deep vessels of the central part of the lower lip run to the submental glands.
Lymphatic Vessels of the Nasal Cavities. - Those from the anterior parts of the nasal cavities communicate with the vessels
of the integument of the nose and end in the submaxillary glands; those from the posterior two-thirds of the nasal cavities
and from the accessory air sinuses pass partly to the retropharyngeal and partly to the superior deep cervical glands.
Lymphatic Vessels of the Mouth. - The vessels of the gums pass to the submaxillary glands; those of the hard palate are
continuous in front with those of the upper gum, but pass backward to pierce the Constrictor pharyngis superior and end in
the superior deep cervical and subparotid glands; those of the soft palate pass backward and lateralward and end partly in
the retropharyngeal and subparotid, and partly in the superior deep cervical glands. The vessels of the anterior part of the
floor of the mouth pass either directly to the inferior glands of the superior deep cervical group, or indirectly through the
submental glands; from the rest of the floor of the mouth the vessels pass to the submaxillary and superior deep cervical
glands.
The lymphatic vessels of the palatine tonsil, usually three to five in number, pierce the buccopharyngeal fascia and constrictor pharyngis superior and pass between the Stylohyoideus and internal jugular vein to the uppermost of the superior
deep cervical glands. They end in a gland which lies at the side of the posterior belly of the Digastricus, on the internal jugular vein; occasionally one or two additional vessels run to small glands on the lateral side of the vein under cover of the
Sternocleidomastoideus.
The lymphatic vessels of the tongue are drained chiefly into the deep cervical glands lying between the posterior belly of
the Digastricus and the superior belly of the Omohyoideus; one gland situated at the bifurcation of the common carotid
artery is so intimately associated with these vessels that it is known as the principal gland of the tongue. The lymphatic
vessels of the tongue may be divided into four groups: (1) apical, from the tip of the tongue to the suprahyoid glands and
principal gland of the tongue; (2) lateral, from the margin of the tongue - some of these pierce the Mylohyoideus to end in
the submaxillary glands, others pass down on the Hyoglossus to the superior deep cervical glands; (3) basal, from the region of the vallate papillae to the superior deep cervical glands; and (4) median, a few of which perforate the Mylohyoideus
to reach the submaxillary glands, while the majority turn around the posterior border of the muscle to enter the superior
deep cervical glands.
The Lymph Glands of the Neck - The lymph glands of the neck include the following groups:
Submaxillary. Superficial Cervical.
Submental.
Anterior Cervical.
Deep Cervical.
The submaxillary glands (lymphoglandulae submaxillares), three to six in number, are placed beneath the body of the
mandible in the submaxillary triangle, and rest on the superficial surface of the submaxillary salivary gland. One gland, the
middle gland of Stahr, which lies on the external maxillary artery as it turns over the mandible, is the most constant of the
series; small lymph glands are sometimes found on the deep surface of the submaxillary salivary glands. The afferents of
the submaxillary glands drain the medial palpebral commissure, the cheek, the side of the nose, the upper lip, the lateral
part of the lower lip, the gums, and the anterior part of the margin of the tongue; efferent vessels from the facial and submental glands also enter the submaxillary glands. Their efferent vessels pass to the superior deep cervical glands.
The submental or suprahyoid glands are situated between the anterior bellies of the Digastrici. Their afferents drain the
central portions of the lower lip and floor of the mouth and the apex of the tongue; their efferents pass partly to the submaxillary glands and partly to a gland of the deep cervical group situated on the internal jugular vein at the level of the cricoid
cartilage.
The superficial cervical glands (lymphoglandulae cervicales superficiales) lie in close relationship with the external jugular vein as it emerges from the parotid gland, and, therefore, superficial to the Sternocleidomastoideus. Their afferents drain
the lower parts of the auricula and parotid region, while their efferents pass around the anterior margin of the Sternocleidomastoideus to join the superior deep cervical glands.
The anterior cervical glands form an irregular and inconstant group on the front of the larynx and trachea. They may be
divided into (a) a superficial set, placed on the anterior jugular vein; (b) a deeper set, which is further subdivided into
prelaryngeal, on the middle cricothyroid ligament, and pretracheal, on the front of the trachea. This deeper set drains the
lower part of the larynx, the thyroid gland, and the upper part of the trachea; its efferents pass to the lowest of the superior
deep cervical glands.
The deep cervical glands (lymphoglandulae cervicales profundae) are numerous and of large size: they form a chain along
the carotid sheath, lying by the side of the pharynx, esophagus, and trachea, and extending from the base of the skull to the
root of the neck. They are usually described in two groups: (1) the superior deep cervical glands lying under the Sternocleidomastoideus in close relation with the accessory nerve and the internal jugular vein, some of the glands lying in
front of and others behind the vessel; (2) the inferior deep cervical glands extending beyond the posterior margin of the
Sternocleidomastoideus into the supraclavicular triangle, where they are closely related to the brachial plexus and subclavian vein. A few minute paratracheal glands are situated alongside the recurrent nerves on the lateral aspects of the trachea
and esophagus. The superior deep cervical glands drain the occipital portion of the scalp, the auricula, the back of the neck,
a considerable part of the tongue, the larynx, thyroid gland, trachea, nasal part of the pharynx, nasal cavities, palate, and
esophagus. They receive also the efferent vessels from all the other glands of the head and neck, except those from the inferior deep cervical glands. The inferior deep cervical glands drain the back of the scalp and neck, the superficial pectoral
region, part of the arm, and, occasionally, part of the superior surface of the liver, In addition, they receive vessels from the
superior deep cervical glands. The efferents of the superior deep cervical glands pass partly to the inferior deep cervical
glands and partly to a trunk which unites with the efferent vessel of the inferior deep cervical glands and forms the jugular
trunk. On the right side, this trunk ends in the junction of the internal jugular and subclavian veins; on the left side it joins
the thoracic duct.
The lymphatic vessels of the skin and muscles of the neck pass to the deep cervical glands. From the upper part of the
pharynx the lymphatic vessels pass to the retropharyngeal, from the lower part to the deep cervical glands. From the larynx
two sets of vessels arise, an upper and a lower. The vessels of the upper set pierce the hyothyroid membrane and join the
superior deep cervical glands. Of the lower set, some pierce the conus elasticus and join the pretracheal and prelaryngeal
glands; others run between the cricoid and first tracheal ring and enter the inferior deep cervical glands. The lymphatic vessels of the thyroid gland consist of two sets, an upper, which accompanies the superior thyroid artery and enters the superior deep cervical glands, and a lower, which runs partly to the pretracheal glands and partly to the small paratracheal glands
which accompany the recurrent nerves. These latter glands receive also the lymphatic vessels from the cervical portion of
the trachea.
The Lymph Glands of the Upper Extremity - The lymph glands of the upper extremity are divided into two sets, superficial
and deep.
The superficial lymph glands are few and of small size. One or two supratrochlear glands are placed above the medial epicondyle of the humerus, medial to the basilic vein. Their afferents drain the middle, ring, and little fingers, the medial por-
tion of the hand, and the superficial area over the ulnar side of the forearm; these vessels are, however, in free communication with the other lymphatic vessels of the forearm. Their efferents accompany the basilic vein and join the deeper vessels.
One or two deltoideopectoral glands are found beside the cephalic vein, between the Pectoralis major and Deltoideus, immediately below the clavicle. They are situated in the course of the external collecting trunks of the arm.
The deep lymph glands are chiefly grouped in the axilla, although a few may be found in the forearm, in the course of the
radial, ulnar, and interosseous vessels, and in the arm along the medial side of the brachial artery.
The Axillary Glands (lymphoglandulae axillares) are of large size, vary from twenty to thirty in number, and may be arranged in the following groups:
1. A lateral group of from four to six glands lies in relation to the medial and posterior aspects of the axillary vein; the
afferents of these glands drain the whole arm with the exception of that portion whose vessels accompany the cephalic vein.
The efferent vessels pass partly to the central and subclavicular groups of axillary glands and partly to the inferior deep
cervical glands.
2. An anterior or pectoral group consists of four or five glands along the lower border of the Pectoralis minor, in relation
with the lateral thoracic artery. Their afferents drain the skin and muscles of the anterior and lateral thoracic walls, and the
central and lateral parts of the namma; their efferents pass partly to the central and partly to the subclavicular groups of
axillary glands.
3. A posterior or subscapular group of six or seven glands is placed along the lower margin of the posterior wall of the
axilla in the course of the subscapular artery. The afferents of this group drain the skin and muscles of the lower part of the
back of the neck and of the posterior thoracic wall; their efferents pass to the central group of axillary glands.
4. A central or intermediate group of three or four large glands is imbedded in the adipose tissue near the base of the axilla. Its afferents are the efferent vessels of all the preceding groups of axillary glands; its efferents pass to the subclavicular
group.
5. A medial or subclavicular group of six to twelve glands is situated partly posterior to the upper portion of the Pectoralis
minor and partly above the upper border of this muscle. Its only direct territorial afferents are those which accompany the
cephalic vein and one which drains the upper peripheral part of the mamma, but it receives the efferents of all the other
axillary glands. The efferent vessels of the subclavicular group unite to form the subclavian trunk, which opens either directly into the junction of the internal jugular and subclavian veins or into the jugular lymphatic trunk; on the left side it
may end in the thoracic duct. A few efferents from the subclavicular glands usually pass to the inferior deep cervical
glands.
The Lymphatic Vessels of the Upper Extremity - The lymphatic vessels of the upper extremity are divided into two sets,
superficial and deep.
The superficial lymphatic vessels commence in the lymphatic plexus which everywhere pervades the skin; the meshes of
the plexus are much finer in the palm and on the flexor aspect of the digits than elsewhere. The digital plexuses are drained
by a pair of vessels which run on the sides of each digit, and incline backward to reach the dorsum of the hand. From the
dense plexus of the palm, vessels pass in different directions, viz., upward toward the wrist, downward to join the digital
vessels, medialward to join the vessels on the ulnar border of the hand, and lateralward to those on the thumb. Several vessels from the central part of the plexus unite to form a trunk, which passes around the metacarpal bone of the index finger
to join the vessels on the back of that digit and on the back of the thumb. Running upward in front of and behind the wrist,
the lymphatic vessels are collected into radial, median, and ulnar groups, which accompany respectively the cephalic, median, and basilic veins in the forearm. A few of the ulnar lymphatics end in the supratrochlear glands, but the majority pass
directly to the lateral group of axillary glands. Some of the radial vessels are collected into a trunk which ascends with the
cephalic vein to the deltoideopectoral glands; the efferents from this group pass either to the subclavicular axillary glands
or to the inferior cervical glands.
The deep lymphatic vessels accompany the deep bloodvessels. In the forearm, they consist of four sets, corresponding
with the radial, ulnar, volar, and dorsal interosseous arteries; they communicate at intervals with the superficial lymphatics,
and some of them end in the glands which are occasionally found beside the arteries. In their course upward, a few end in
the glands which lie upon the brachial artery; but most of them pass to the lateral group of axillary glands.
The Lymph Glands of the Lower Extremity - The lymph glands of the lower extremity consist of the anterior tibial gland
and the popliteal and inguinal glands.
The anterior tibial gland (lymphoglandula tibialis anterior) is small and inconstant. It lies on the interosseous membrane in
relation to the upper part of the anterior tibial vessels, and constitutes a substation in the course of the anterior tibial lymphatic trunks.
The popliteal glands (lymphoglandulae popliteae), small in size and some six or seven in number, are imbedded in the fat
contained in the popliteal fossa. One lies immediately beneath the popliteal fascia, near the terminal part of the small saphenous vein, and drains the region from which this vein derives its tributaries. Another is placed between the popliteal
artery and the posterior surface of the knee-joint; it receives the lymphatic vessels from the knee-joint together with those
which accompany the genicular arteries. The others lie at the sides of the popliteal vessels, and receive as efferents the
trunks which accompany the anterior and posterior tibial vessels. The efferents of the popliteal glands pass almost entirely
alongside the femoral vessels to the deep inguinal glands, but a few may accompany the great saphenous vein, and end in
the glands of the superficial subinguinal group.
The inguinal glands (lymphoglandulae inguinales), from twelve to twenty in number, are situated at the upper part of the
femoral triangle. They may be divided into two groups by a horizontal line at the level of the termination of the great sa-
phenous vein; those lying above this line are termed the superficial inguinal glands, and those below it the subinguinal
glands, the latter group consisting of a superficial and a deep set.
The Superficial Inguinal Glands form a chain immediately below the inguinal ligament. They receive as afferents lymphatic vessels from the integument of the penis, scrotum, perineum, buttock, and abdominal wall below the level of the
umbilicus.
The Superficial Subinguinal Glands (lymphoglandulae subinguinales superficiales) are placed on either side of the upper
part of the great saphenous vein; their efferents consist chiefly of the superficial lymphatic vessels of the lower extremity;
but they also receive some of the vessels which drain the integument of the penis, scrotum, perineum, and buttock.
The Deep Subinguinal Glands (lymphoglandulae subinguinales profundae) vary from one to three in number, and are
placed under the fascia lata, on the medial side of the femoral vein. When three are present, the lowest is situated just below
the junction of the great saphenous and femoral veins, the middle in the femoral canal, and the highest in the lateral part of
the femoral ring. The middle one is the most inconstant of the three, but the highest, the gland of Cloquet or Rosenmüller,
is also frequently absent. They receive as afferents the deep lymphatic trunks which accompany the femoral vessels, the
lymphatics from the glans penis vel clitoridis, and also some of the efferents from the superficial subinguinal glands.
The Lymphatic Vessels of the Lower Extremity - The lymphatic vessels of the lower extremity consist of two sets, superficial and deep, and in their distribution correspond closely with the veins.
The superficial lymphatic vessels lie in the superficial fascia, and are divisible into two groups: a medial, which follows
the course of the great saphenous vein, and a lateral, which accompanies the small saphenous vein. The vessels of the medial group are larger and more numerous than those of the lateral group, and commence on the tibial side and dorsum of the
foot; they ascend both in front of and behind the medial malleolus, run up the leg with the great saphenous vein, pass with
it behind the medial condyle of the femur, and accompany it to the groin, where they end in the subinguinal group of superficial glands. The vessels of the lateral group arise from the fibular side of the foot; some ascend in front of the leg, and,
just below the knee, cross the tibia to join the lymphatics on the medial side of the thigh; others pass behind the lateral malleolus, and, accompanying the small saphenous vein, enter the popliteal glands.
The deep lymphatic vessels are few in number, and accompany the deep bloodvessels. In the leg, they consist of three
sets, the anterior tibial, posterior tibial, and peroneal, which accompany the corresponding bloodvessels, two or three with
each artery; they enter the popliteal lymph glands.
The deep lymphatic vessels of the gluteal and ischial regions follow the course of the corresponding bloodvessels. Those
accompanying the superior gluteal vessels end in a gland which lies on the intrapelvic portion of the superior gluteal artery
near the upper border of the greater sciatic foramen. Those following the inferior gluteal vessels traverse one or two small
glands which lie below the Piriformis muscle, and end in the hypogastric glands.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 35. Anatomy of organs of immune system.
The aim: to learn the structure and relations of aorta and its main branches.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, cardiologists etc.
The plan of the practice class:
A. Checking of home assignment: oral quiz, written test control, control of practice skills – 30 minutes.
B. Summary lecture on the topic by teacher – 20 minutes.
C. Students’ self-taught time – 25 minutes
D. Home-task – 5 minutes
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Self-taught class 14. Heart and blood circulation development.
The aim: to learn the development of cardiovascular system and peculiarities of fetal haemodynamics.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, obstetritians, cardiologista and cardiac surgeons etc.
Development of the Vascular System
Bloodvessels first make their appearance in several scattered vascular areas which are developed simultaneously between
the entoderm and the mesoderm of the yolk-sac, i. e., outside the body of the embryo. Here a new type of cell, the angioblast or vasoformative cell, is differentiated from the mesoderm. These cells as they divide form small, dense syncytial
masses which soon join with similar masses by means of fine processes to form plexuses. These plexuses increase both by
division and growth of its cells and by the addition of new angioblasts which differentiate from the mesoderm. Within these
solid plexuses and also within the isolated masses of angioblasts vacuoles appear through liquefaction of the central part of
the syncytium into plasma. The lumen of the bloodvessels thus formed is probably intracellular. The flattened cells at the
periphery form the endothelium. The nucleated red blood corpuscles develop either from small masses of the original angioblast left attached to the inner wall of the lumen or directly from the flat endothelial cells. In either case the syncytial mass
thus formed projects from and is attached to the wall of the vessel. Such a mass is known as a blood island and hemoglobin
gradually accumulates within it. Later the cells on the surface round up, giving the mass a mulberry-like appearance. Then
the red blood cells break loose and are carried away in the plasma. Such free blood cells continue to divide. The term blood
island was originally used for the syncytial masses of angioblasts found in the area vasculosa, but it is probably best to limit
the term to the masses within the lumen from which the red blood cells. Blood islands have been seen in the area vasculosa
in the omphalomesenteric vein and arteries, and in the dorsal aorta.
The differentiation of angïoblasts from the mesoderm occurs not only in the area vasculosa but within the embryo and
probably most of the larger bloodvessels are developed in situ in this manner. This process of the differentiation of angioblasts from the mesoderm probably ceases in different regions of the embryo at different periods and after its cessation new
vessels are formed by sprouts from vessels already laid down in the form of capillary plexuses.
The first rudiment of the heart appears as a pair of tubular vessels which are developed in the splanchnopleure of the pericardial area. These are named the primitive aortæ, and a direct continuity is soon established between them and the vessels
of the yolk-sac. Each receives anteriorly a vein—the vitelline vein—from the yolk-sac, and is prolonged backward on the
lateral aspect of the notochord under the name of the dorsal aorta. The dorsal aortæ give branches to the yolk-sac, and are
continued backward through the body-stalk as the umbilical arteries to the villi of the chorion.
The rudiment of the heart is situated immediately below the fore-gut and consists of a short stem. It gives off two vessels,
the primitive aortæ, which run backward, one on either side of the notochord, and then pass into the body-stalk along which
they are carried to the chorion. From the chorionic villi the blood is returned by a pair of umbilical veins which unite in the
body-stalk to form a single vessel and subsequently encircle the mouth of the yolk-sac and open into the heart. At the junction of the yolk-sac and body-stalk each vein is joined by a branch from the vascular plexus of the yolk-sac. From his observations it seems that, in the human embryo, the chorionic circulation is established before that on the yolk-sac.
By the forward growth and flexure of the head the pericardial area and the anterior portions of the primitive aortæ are
folded backward on the ventral aspect of the fore-gut, and the original relation of the somatopleure and splanchnopleure
layers of the pericardial area is reversed. Each primitive aorta now consists of a ventral and a dorsal part connected anteriorly by an arch; these three parts are named respectively the anterior ventral aorta, the dorsal aorta, and the first cephalic
arch. The vitelline veins which enter the embryo through the anterior wall of the umbilical orifice are now continuous with
the posterior ends of the anterior ventral aorta. With the formation of the tail-fold the posterior parts of the primitive aortæ
are carried forward in a ventral direction to form the posterior ventral aortæ and primary caudal arches. In the pericardial
region the two primitive aortæ grow together, and fuse to form a single tubular heart, the posterior end of which receives
the two vitelline veins, while from its anterior end the two anterior ventral aortæ emerge. The first cephalic arches pass
through the mandibular arches, and behind them five additional pairs subsequently develop, so that altogether six pairs of
aortic arches are formed; the fifth arches are very transitory vessels connecting the ventral aortæ with the dorsal ends of the
sixth arches. By the rhythmical contraction of the tubular heart the blood is forced through the aortæ and bloodvessels of
the vascular area, from which it is returned to the heart by the vitelline veins. This constitutes the vitelline circulation, and
by means of it nutriment is absorbed from the yolk (vitellus.)
The vitelline veins at first open separately into the posterior end of the tubular heart, but after a time their terminal portions fuse to form a single vessel. The vitelline veins ultimately drain the blood from the digestive tube, and are modified to
form the portal vein. This is caused by the growth of the liver, which interrupts their direct continuity with the heart; and
the blood returned by them circulates through the liver before reaching the heart.
With the atrophy of the yolk-sac the vitelline circulation diminishes and ultimately ceases, while an increasing amount of
blood is carried through the umbilical arteries to the villi of the chorion. Subsequently, as the non-placental chorionic villi
atrophy, their vessels disappear; and then the umbilical arteries convey the whole of their contents to the placenta, whence
it is returned to the heart by the umbilical veins. In this manner the placental circulation is established, and by means of it
nutritive materials are absorbed from, and waste products given up to the maternal blood.
The umbilical veins, like the vitelline, undergo interruption in the developing liver, and the blood returned by them passes
through this organ before reaching the heart. Ultimately the right umbilical vein shrivels up and disappears.
During the occurrence of these changes great alterations take place in the primitive heart and bloodvessels.
Further Development of the Heart.—Between the endothelial lining and the outer wall of the heart there exists for a time an
intricate trabecular network of mesodermal tissue from which, at a later stage, the musculi papillares, chordæ tendineæ, and
trabeculæ are developed. The simple tubular heart, already described, becomes elongated and bent on itself so as to form an
S-shaped loop, the anterior part bending to the right and the posterior part to the left. The intermediate portion arches transversely from left to right, and then turns sharply forward into the anterior part of the loop. Slight constrictions make their
appearance in the tube and divide it from behind forward into five parts. viz.: (1) the sinus venosus; (2) the primitive atrium; (3) the primitive ventricle; (4) the bulbus cordis, and (5) the truncus arteriosus. The constriction between the atrium
and ventricle constitutes the atrial canal, and indicates the site of the future atrioventricular valves.
The sinus venosus is at first situated in the septum transversum (a layer of mesoderm in which the liver and the central
tendon of the diaphragm are developed) behind the primitive atrium, and is formed by the union of the vitelline veins. The
veins or ducts of Cuvier from the body of the embryo and the umbilical veins from the placenta subsequently open into it.
The sinus is at first place transversely, and opens by a median aperture into the primitive atrium. Soon, however, it assumes
an oblique position, and becomes crescentic in form; its right half or horn increases more rapidly than the left, and the
opening into the atrium now communicates with the right portion of the atrial cavity. The right horn and transverse portion
of the sinus ultimately become incorporated with and form a part of the adult right atrium, the line of union between it and
the auricula being indicated in the interior of the atrium by a vertical crest, the crista terminalis of His. The left horn, which
ultimately receives only the left duct of Cuvier, persists as the coronary sinus. The vitelline and umbilical veins are soon
replaced by a single vessel, the inferior vena cava, and the three veins (inferior vena cava and right and left Cuvierian
ducts) open into the dorsal aspect of the atrium by a common slit-like aperture. The upper part of this aperture represents
the opening of the permanent superior vena cava, the lower that of the inferior vena cava, and the intermediate part the orifice of the coronary sinus. The slit-like aperture lies obliquely, and is guarded by two halves, the right and left venous
valves; above the opening these unite with each other and are continuous with a fold named the septum spurium; below the
opening they fuse to form a triangular thickening—the spina vestibuli. The right venous valve is retained; a small septum,
the sinus septum, grows from the posterior wall of the sinus venosus to fuse with the valve and divide it into two parts—an
upper, the valve of the inferior vena cava, and a lower, the valve of the coronary sinus. The extreme upper portion of the
right venous valve, together with the septum spurium, form the crista terminalis already mentioned. The upper and middle
thirds of the left venous valve disappear; the lower third is continued into the spina vestibuli, and later fuses with the septum secundum of the atria and takes part in the formation of the limbus fossæ ovalis.
The atrial canal is at first a short straight tube connecting the atrial with the ventricular portion of the heart, but its growth
is relatively slow, and it becomes overlapped by the atria and ventricles so that its position on the surface of the heart is
indicated only by an annular constriction. Its lumen is reduced to a transverse slit, and two thickenings appear, one on its
dorsal and another on its ventral wall. These thickenings, or endocardial cushions as they are termed, project into the canal,
and, meeting in the middle line, unite to form the septum intermedium which divides the canal into two channels, the future
right and left atrioventricular orifices.
The primitive atrium grows rapidly and partially encircles the bulbus cordis; the groove against which the bulbus cordis
lies is the first indication of a division into right and left atria. The cavity of the primitive atrium becomes subdivided into
right and left chambers by a septum, the septum primum, which grows downward into the cavity. For a time the atria communicate with each other by an opening, the ostium primum of Born, below the free margin of the septum. This opening is
closed by the union of the septum primum with the septum intermedium, and the communication between the atria is
reëstablished through an opening which is developed in the upper part of the septum primum; this opening is known as the
foramen ovale (ostium secundum of Born) and persists until birth. A second septum, the septum secundum, semilunar in
shape, grows downward from the upper wall of the atrium immediately to the right of the primary septum and foramen ovale. Shortly after birth it fuses with the primary septum, and by this means the foramen ovale is closed, but sometimes the
fusion is incomplete and the upper part of the foramen remains patent. The limbus fossæ ovalis denotes the free margin of
the septum secundum. Issuing from each lung is a pair of pulmonary veins; each pair unites to form a single vessel, and
these in turn join in a common trunk which opens into the left atrium. Subsequently the common trunk and the two vessels
forming it expand and form the vestibule or greater part of the atrium, the expansion reaching as far as the openings of the
four vessels, so that in the adult all four veins open separately into the left atrium.
The primitive ventricle becomes divided by a septum, the septum inferius or ventricular septum, which grows upward
from the lower part of the ventricle, its position being indicated on the surface of the heart by a furrow. Its dorsal part increases more rapidly than its ventral portion, and fuses with the dorsal part of the septum intermedium. For a time an interventricular foramen exists above its ventral portion, but this foramen is ultimately closed by the fusion of the aortic septum
with the ventricular septum.
When the heart assumes its S-shaped form the bulbus cordis lies ventral to and in front of the primitive ventricle. The adjacent walls of the bulbus cordis and ventricle approximate, fuse, and finally disappear, and the bulbus cordis now communicates freely with the right ventricle, while the junction of the bulbus with the truncus arteriosus is brought directly
ventral to and applied to the atrial canal. By the upgrowth of the ventricular septum the bulbus cordis is in great measure
separated from the left ventricle, but remains an integral part of the right ventricle, of which it forms the infundibulum.
The truncus arteriosus and bulbus cordis are divided by the aortic septum. This makes its appearance in three portions. (1)
Two distal ridge-like thickenings project into the lumen of the tube; these increase in size, and ultimately meet and fuse to
form a septum, which takes a spiral course toward the proximal end of the truncus arteriosus. It divides the distal part of the
truncus into two vessels, the aorta and pulmonary artery, which lie side by side above, but near the heart the pulmonary
artery is in front of the aorta. (2) Four endocardial cushions appear in the proximal part of the truncus arteriosus in the region of the future semilunar valves; the manner in which these are related to the aortic septum is described below. (3) Two
endocardial thickenings—anterior and posterior—develop in the bulbus cordis and unite to form a short septum; this joins
above with the aortic septum and below with the ventricular septum. The septum grows down into the ventricle as an
oblique partition, which ultimately blends with the ventricular septum in such a way as to bring the bulbus cordis into
communication with the pulmonary artery, and through the latter with the sixth pair of aortic arches; while the left ventricle
is brought into continuity with the aorta, which communicates with the remaining aortic arches.
The Valves of the Heart.—The atrioventricular valves are developed in relation to the atrial canal. By the upward expansion of the bases of the ventricles the canal becomes invaginated into the ventricular cavities. The invaginated margin
forms the rudiments of the lateral cusps of the atrioventricular valves; the mesial or septal cusps of the valves are developed
as downward prolongations of the septum intermedium. The aortic and pulmonary semilunar valves are formed from four
endocardial thickenings—an anterior, a posterior, and two lateral—which appear at the proximal end of the truncus arterio-
sus. As the aortic septum grows downward it divides each of the lateral thickenings into two, thus giving rise to six thickenings—the rudiments of the semilunar valves—three at the aortic and three at the pulmonary orifice.
Further Development of the Arteries.—Recent observations show that practically none of the main vessels of the adult arise
as such in the embryo. In the site of each vessel a capillary network forms, and by the enlargement of definite paths in this
the larger arteries and veins are developed. The branches of the main arteries are not always simple modifications of the
vessels of the capillary network, but may arise as new outgrowths from the enlarged stem.
It has been seen that each primitive aorta consists of a ventral and a dorsal part which are continuous through the first aortic arch. The dorsal aortæ at first run backward separately on either side of the notochord, but about the third week they
fuse from about the level of the fourth thoracic to that of the fourth lumbar segment to form a single trunk, the descending
aorta. The first aortic arches run through the mandibular arches, and behind them five additional pairs are developed within
the visceral arches; so that, in all, six pairs of aortic arches are formed. The first and second arches pass between the ventral
and dorsal aortæ, while the others arise at first by a common trunk from the truncus arteriosus, but end separately in the
dorsal aortæ. As the neck elongates, the ventral aortæ are drawn out, and the third and fourth arches arise directly from
these vessels.
In fishes these arches persist and give off branches to the gills, in which the blood is oxygenated. In mammals some of
them remain as permanent structures while others disappear or become obliterated.
The Anterior Ventral Aortæ.—These persist on both sides. The right forms (a) the innominate artery, (b) the right common
and external carotid arteries. The left gives rise to (a) the short portion of the aortic arch, which reaches from the origin of
the innominate artery to that of the left common carotid artery; (b) the left common and external carotid arteries.
The Aortic Arches.—The first and second arches disappear early, but the dorsal end of the second gives origin to the stapedial artery, a vessel which atrophies in man but persists in some mammals. It passes through the ring of the stapes and divides into supraorbital, infraorbital, and mandibular branches which follow the three divisions of the trigeminal nerve. The
infraorbital and mandibular arise from a common stem, the terminal part of which anastomoses with the external carotid.
On the obliteration of the stapedial artery this anastomosis enlarges and forms the internal maxillary artery, and the branches of the stapedial artery are now branches of this vessel. The common stem of the infraorbital and mandibular branches
passes between the two roots of the auriculotemporal nerve and becomes the middle meningeal artery; the original supraorbital branch of the stapedial is represented by the orbital twigs of the middle meningeal. The third aortic arch constitutes the
commencement of the internal carotid artery, and is therefore named the carotid arch. The fourth right arch forms the right
subclavian as far as the origin of its internal mammary branch; while the fourth left arch constitutes the arch of the aorta
between the origin of the left carotid artery and the termination of the ductus arteriosus. The fifth arch disappears on both
sides. The sixth right arch disappears; the sixth left arch gives off the pulmonary arteries and forms the ductus arteriosus;
this duct remains pervious during the whole of fetal life, but is obliterated a few days after birth. His showed that in the
early embryo the right and left arches each gives a branch to the lungs, but that later both pulmonary arteries take origin
from the left arch.
The Dorsal Aortæ.—In front of the third aortic arches the dorsal aortæ persist and form the continuations of the internal
carotid arteries; these arteries pass to the brain and each divides into an anterior and a posterior branch, the former giving
off the ophthalmic and the anterior and middle cerebral arteries, while the latter turns back and joins the cerebral part of the
vertebral artery. Behind the third arch the right dorsal aorta disappears as far as the point where the two dorsal aortæ fuse to
form the descending aorta. The part of the left dorsal aorta between the third and fourth arches disappears, while the remainder persists to form the descending part of the arch of the aorta. A constriction, the aortic isthmus, is sometimes seen
in the aorta between the origin of the left subclavian and the attachment of the ductus arteriosus.
Sometimes the right subclavian artery arises from the aortic arch distal to the origin of the left subclavian and passes upward and to the right behind the trachea and esophagus. This condition may be explained by the persistence of the right
dorsal aorta and the obliteration of the fourth right arch.
In birds the fourth right arch forms the arch of the aorta; in reptiles the fourth arch on both sides persists and gives rise to
the double aortic arch in these animals.
The heart originally lies on the ventral aspect of the pharynx, immediately behind the stomodeum. With the elongation of
the neck and the development of the lungs it recedes within the thorax, and, as a consequence, the anterior ventral aortæ are
drawn out and the original position of the fourth and fifth arches is greatly modified. Thus, on the right side the fourth recedes to the root of the neck, while on the left side it is withdrawn within the thorax. The recurrent nerves originally pass to
the larynx under the sixth pair of arches, and are therefore pulled backward with the descent of these structures, so that in
the adult the left nerve hooks around the ligamentum arteriosum; owing to the disappearance of the fifth and the sixth right
arches the right nerve hooks around that immediately above them, i.e., the commencement of the subclavian artery. Segmental arteries arise from the primitive dorsal aortæ and course between successive segments. The seventh segmental artery is of special interest, since it forms the lower end of the vertebral artery and, when the forelimb bud appears, sends a
branch to it (the subclavian artery). From the seventh segmental arteries the entire left subclavian and the greater part of the
right subclavian are formed. The second pair of segmental arteries accompany the hypoglossal nerves to the brain and are
named the hypoglossal arteries. Each sends forward a branch which forms the cerebral part of the vertebral artery and anastomoses with the posterior branch of the internal carotid. The two vertebrals unite on the ventral surface of the hind-brain to
form the basilar artery. Later the hypoglossal artery atrophies and the vertebral is connected with the first segmental artery.
The cervical part of the vertebral is developed from a longitudinal anastomosis between the first seven segmental arteries,
so that the seventh of these ultimately becomes the source of the artery. As a result of the growth of the upper limb the subclavian artery increases greatly in size and the vertebral then appears to spring from it.
Recent observations show that several segmental arteries contribute branches to the upper limb-bud and form in it a free
capillary anastomosis. Of these branches, only one, viz., that derived from the seventh segmental artery, persists to form the
subclavian artery. The subclavian artery is prolonged into the limb under the names of the axillary and brachial arteries, and
these together constitute the arterial stem for the upper arm, the direct continuation of this stem in the forearm is the volar
interosseous artery. A branch which accompanies the median nerve soon increases in size and forms the main vessel (median artery) of the forearm, while the volar interosseous diminishes. Later the radial and ulnar arteries are developed as
branches of the brachial part of the stem and coincidently with their enlargement the median artery recedes; occasionally it
persists as a vessel of some considerable size and then accompanies the median nerve into the palm of the hand.
The primary arterial stem for the lower limb is formed by the inferior gluteal (sciatic) artery, which accompanies the sciatic nerve along the posterior aspect of the thigh to the back of the knee, whence it is continued as the peroneal artery. This
arrangement exists in reptiles and amphibians. The femoral artery arises later as a branch of the common iliac, and, passing
down the front and medial side of the thigh to the bend of the knee, joins the inferior gluteal artery. The femoral quickly
enlarges, and, coincidently with this, the part of the inferior gluteal immediately above the knee undergoes atrophy. The
anterior and posterior tibial arteries are branches of the main arterial stem.
Further Development of the Veins.—The formation of the great veins of the embryo may be best considered by dividing
them into two groups, visceral and parietal.
The Visceral Veins.—The visceral veins are the two vitelline or omphalomesenteric veins bringing the blood from the
yolk-sac, and the two umbilical veins returning the blood from the placenta; these four veins open close together into the
sinus venosus.
The Vitelline Veins run upward at first in front, and subsequently on either side of the intestinal canal. They unite on the
ventral aspect of the canal, and beyond this are connected to one another by two anastomotic branches, one on the dorsal,
and the other on the ventral aspect of the duodenal portion of the intestine, which is thus encircled by two venous rings;
into the middle or dorsal anastomosis the superior mesenteric vein opens. The portions of the veins above the upper ring
become interrupted by the developing liver and broken up by it into a plexus of small capillary-like vessels termed sinusoids. The branches conveying the blood to this plexus are named the venæ advehentes, and become the branches of the portal vein; while the vessels draining the plexus into the sinus venosus are termed the venæ revehentes, and form the future
hepatic veins. Ultimately the left vena revehens no longer communicates directly with the sinus venosus, but opens into the
right vena revehens. The persistent part of the upper venous ring, above the opening of the superior mesenteric vein, forms
the trunk of the portal vein.
The two Umbilical Veins fuse early to form a single trunk in the body-stalk, but remain separate within the embryo and
pass forward to the sinus venosus in the side walls of the body. Like the vitelline veins, their direct connection with the
sinus venosus becomes interrupted by the developing liver, and thus at this stage the whole of the blood from the yolk-sac
and placenta passes through the substance of the liver before it reaches the heart. The right umbilical and right vitelline
veins shrivel and disappear; the left umbilical, on the other hand, becomes enlarged and opens into the upper venous ring of
the vitelline veins; with the atrophy of the yolk-sac the left vitelline vein also undergoes atrophy and disappears. Finally a
direct branch is established between this ring and the right hepatic vein; this branch is named the ductus venosus, and, enlarging rapidly, it forms a wide channel through which most of the blood, returned from the placenta, is carried direct to the
heart without passing through the liver. A small proportion of the blood from the placenta is, however, conveyed from the
left umbilical vein to the liver through the left vena advehens. The left umbilical vein and the ductus venosus undergo atrophy and obliteration after birth, and form respectively the ligamentum teres and ligamentum venosum of the liver.
The Parietal Veins.—The first indication of a parietal system consists in the appearance of two short transverse veins, the
ducts of Cuvier, which open, one on either side, into the sinus venosus. Each of these ducts receives an ascending and descending vein. The ascending veins return the blood from the parietes of the trunk and from the Wolffian bodies, and are
called cardinal veins. The descending veins return the blood from the head, and are called primitive jugular veins. The
blood from the lower limbs is collected by the right and left iliac and hypogastric veins, which, in the earlier stages of development, open into the corresponding right and left cardinal veins; later, a transverse branch (the left common iliac vein)
is developed between the lower parts of the two cardinal veins, and through this the blood is carried into the right cardinal
vein. The portion of the left cardinal vein below the left renal vein atrophies and disappears up to the point of entrance of
the left spermatic vein; the portion above the left renal vein persists as the hemiazygos and accessory hemiazygos veins and
the lower portion of the highest left intercostal vein. The right cardinal vein which now receives the blood from both lower
extremities, forms a large venous trunk along the posterior abdominal wall; up to the level of the renal veins it forms the
lower part of the inferior vena cava. Above the level of the renal veins the right cardinal vein persists as the azygos vein
and receives the right intercostal veins, while the hemiazygos veins are brought into communication with it by the development of transverse branches in front of the vertebral column.
Inferior Vena Cava.—The development of the inferior vena cava is associated with the formation of two veins, the subcardinal veins. These lie parallel to, and on the ventral aspect of, the cardinal veins, and originate as longitudinal anastomosing
channels which link up the tributaries from the mesentery to the cardinal veins; they communicate with the cardinal veins
above and below, and also by a series of transverse branches. The two subcardinals are for a time connected with each other in front of the aorta by cross branches, but these disappear and are replaced by a single transverse channel at the level
where the renal veins join the cardinals, and at the same level a cross communication is established on either side between
the cardinal and subcardinal. The portion of the right subcardinal behind this cross communication disappears, while that in
front, i.e., the prerenal part, forms a connection with the ductus venosus at the point of opening of the hepatic veins, and,
rapidly enlarging, receives the blood from the postrenal part of the right cardinal through the cross communication referred
to. In this manner a single trunk, the inferior vena cava, is formed, and consists of the proximal part of the ductus venosus,
the prerenal part of the right subcardinal vein, the postrenal part of the right cardinal vein, and the cross branch which joins
these two veins. The left subcardinal disappears, except the part immediately in front of the renal vein, which is retained as
the left suprarenal vein. The spermatic (or ovarian) vein opens into the postrenal part of the corresponding cardinal vein.
This portion of the right cardinal, as already explained, forms the lower part of the inferior vena cava, so that the right
spermatic opens directly into that vessel. The postrenal segment of the left cardinal disappears, with the exception of the
portion between the spermatic and renal vein, which is retained as the terminal part of the left spermatic vein.
In consequence of the atrophy of the Wolffian bodies the cardinal veins diminish in size; the primitive jugular veins, on
the other hand, become enlarged, owing to the rapid development of the head and brain. They are further augmented by
receiving the veins (subclavian) from the upper extremities, and so come to form the chief veins of the Cuvierian ducts;
these ducts gradually assume an almost vertical position in consequence of the descent of the heart into the thorax. The
right and left Cuvierian ducts are originally of the same diameter, and are frequently termed the right and left superior venæ
cavæ. By the development of a transverse branch, the left innominate vein between the two primitive jugular veins, the
blood is carried across from the left to the right primitive jugular. The portion of the right primitive jugular vein between
the left innominate and the azygos vein forms the upper part of the superior vena cava of the adult; the lower part of this
vessel, i.e., below the entrance of the azygos vein, is formed by the right Cuvierian duct. Below the origin of the transverse
branch the left primitive jugular vein and left Cuvierian duct atrophy, the former constituting the upper part of the highest
left intercostal vein, while the latter is represented by the ligament of the left vena cava, vestigial fold of Marshall, and the
oblique vein of the left atrium, oblique vein of Marshall. Both right and left superior venæ cavæ are present in some animals, and are occasionally found in the adult human being. The oblique vein of the left atrium passes downward across the
back of the left atrium to open into the coronary sinus, which, as already indicated, represents the persistent left horn of the
sinus venosus.
Venous Sinuses of the Dura Mater.—The primary arrangement for drainage of the capillaries of the head consists of a primary head vein which starts in the region of the midbrain and runs caudalward along the side of the brain tube to terminate
at the duct of Cuvier. The primary head vein drains three plexuses of capillaries: the anterior dural plexus, the middle dural
plexus and the posterior dural plexus. The growth of the cartilaginous capsule of the ear and the growth and alteration in
form of the brain bring about changes in this primary arrangement. Owing to the growth of the otic capsule and middle ear
the course of the primary head vein becomes unfavorable and a segment of it becomes obliterated. To make the necessary
adjustment an anastomosis is established above the otic capsule and the middle plexus drains into the posterior plexus.
Then the anteror plexus fuses with the middle plexus and drains through it and the newly established channel, dorsal to the
otic capsule. All that remains of the primary head vein is the cardinal portion or internal jugular and the part in the region of
the trigeminal nerve which may be called the cavernous sinus. Into it drain the orbital veins. The drainage from the cavernous sinus is now upward through the original trunk of the middle plexus, which is now the superior petrosal sinus, into the
newly established dorsal channel. This dorsal channel is the transverse sinus. The inferior petrosal sinus appears later. From
the anterior plexus a sagittal plexus extends forward from which develops the superior sagittal sinus. The straight sinus is
formed in the ventral part of the sagittal plexus. As the hemispheres extend backward these sinuses elongate by incorporating the more caudal loops of the plexus. The anterior part of the sinus is completed first.
The external jugular vein at first drains the region behind the ear (posterior auricular) and enters the primitive jugular as a
lateral tributary. A group of veins from the face and lingual region converge to form a common vein, the linguo-facial,
which also terminates in the primitive jugular. Later, cross communications develop between the external jugular and the
linguo-facial, with the result that the posterior group of facial veins is transferred to the external jugular.
Self-taught class 15. Lymphatic nodes of abdomen, thorax, pelvis.
The aim: to learn the routes of lymph drainage from abdominal, thoracic and pelvic walls and viscera.
Professional orientation: knowledge of this topic is essential for any medical practitioner, especially therapeutists, pediatritians, surgeons, oncologists etc.
The Lymphatics of the Abdomen and Pelvis
The parietal glands include the following groups: External Iliac.
Aortic.
Common Iliac. Hypogastric.
Preaortic.
Iliac Circumflex.
Lumbar.
Lateral
Epigastric.
Sacral.
Retroaortic.
The External Iliac Glands, from eight to ten in number, lie along the external iliac vessels. They are arranged in three
groups, one on the lateral, another on the medial, and a third on the anterior aspect of the vessels; the third group is, however, sometimes absent. Their principal afferents are derived from the inguinal and subinguinal glands, the deep lymphatics of
the abdominal wall below the umbilicus and of the adductor region of the thigh, and the lymphatics from the glans penis vel
clitoridis, the membranous urethra, the prostate, the fundus of the bladder, the cervix uteri, and upper part of the vagina.
The Common Iliac Glands, four to six in number, are grouped behind and on the sides of the common iliac artery, one or
two being placed below the bifurcation of the aorta, in front of the fifth lumbar vertebra. They drain chiefly the hypogastric
and external iliac glands, and their efferents pass to the lateral aortic glands.
The Epigastric Glands (lymphoglandulae epigastricae), three or four in number, are placed alongside the lower portion of
the inferior epigastric vessels.
The Iliac Circumflex Glands, two to four in number, are situated along the course of the deep iliac circumflex vessels;
they are sometimes absent.
The Hypogastric Glands (lymphoglandulae hypogastricae; internal iliac gland) surround the hypogastric vessels, and receive the lymphatics corresponding to the distribution of the branches of the hypogastric artery, i. e., they receive lymphatics from all the pelvic viscera, from the deeper parts of the perineum, including the membranous and cavernous portions of
the urethra, and from the buttock and back of the thigh. An obturator gland is sometimes seen in the upper part of the obturator foramen.
The Sacral Glands are placed in the concavity of the sacrum, in relation to the middle and lateral sacral arteries; they receive lymphatics from the rectum and posterior wall of the pelvis.
The efferents of the hypogastric group end in the common iliac glands.
The Lumbar Glands (lymphoglandulae lumbales) are very numerous, and consist of right and left lateral aortic, preaortic,
and retroaortic groups.
The right lateral aortic glands are situated partly in front of the inferior vena cava, near the termination of the renal vein,
and partly behind it on the origin of the Psoas major, and on the right crus of the diaphragm. The left lateral aortic glands
form a chain on the left side of the abdominal aorta in front of the origin of the Psoas major and left crus of the diaphragm.
The glands on either side receive (a) the efferents of the common iliac glands, (b) the lymphatics from the testis in the male
and from the ovary, uterine tube, and body of the uterus in the female; (c) the lymphatics from the kidney and suprarenal
gland; and (d) the lymphatics draining the lateral abdominal muscles and accompanying the lumbar veins. Most of the efferent vessels of the lateral aortic glands converge to form the right and left lumbar trunks which join the cisterna chyli, but
some enter the pre- and retroaortic glands, and others pierce the crura of the diaphragm to join the lower end of the thoracic
duct. The preaortic glands lie in front of the aorta, and may be divided into celiac, superior mesenteric, and inferior mesenteric groups, arranged around the origins of the corresponding arteries. They receive a few vessels from the lateral aortic
glands, but their principal afferents are derived from the viscera supplied by the three arteries with which they are associated. Some of their efferents pass to the retroaortic glands, but the majority unite to form the intestinal trunk, which enters the
cisterna chyli. The retroaortic glands are placed below the cisterna chyli, on the bodies of the third and fourth lumbar vertebrae. They receive lymphatic trunks from the lateral and preaortic glands, while their efferents end in the cisterna chyli.
The Lymphatic Vessels of the Abdomen and Pelvis
The lymphatic vessels of the walls of the abdomen and pelvis may be divided into two sets, superficial and deep.
The superficial vessels follow the course of the superficial bloodvessels and converge to the superficial inguinal glands;
those derived from the integument of the front of the abdomen below the umbilicus follow the course of the superficial epigastric vessels, and those from the sides of the lumbar part of the abdominal wall pass along the crest of the ilium, with the
superficial iliac circumflex vessels. The superficial lymphatic vessels of the gluteal region turn horizontally around the buttock, and join the superficial inguinal and subinguinal glands.
The deep vessels run alongside the principal bloodvessels. Those of the parietes of the pelvis, which accompany the superior and inferior gluteal, and obturator vessels, follow the course of the hypogastric artery, and ultimately join the lateral
aortic glands.
Lymphatic Vessels of the Perineum and External Genitals. - The lymphatic vessels of the perineum, of the integument of
the penis, and of the scrotum (or vulva), follow the course of the external pudendal vessels, and end in the superficial inguinal and subinguinal glands. Those of the glans penis vel clitoridis terminate partly in the deep subinguinal glands and
partly in the external iliac glands.
The visceral glands are associated with the branches of the celiac, superior and inferior mesenteric arteries. Those related
to the branches of the celiac artery form three sets, gastric, hepatic, and pancreaticolienal.
The Gastric Glands consist of two sets, superior and inferior.
The Superior Gastric Glands (lymphoglandulae gastricae superiores) accompany the left gastric artery and are divisible
into three groups, viz.: (a) upper, on the stem of the artery; (b) lower, accompanying the descending branches of the artery
along the cardiac half of the lesser curvature of the stomach, between the two layers of the lesser omentum; and (c) paracardial outlying members of the gastric glands, disposed in a manner comparable to a chain of beads around the neck of the
stomach. They receive their afferents from the stomach; their efferents pass to the celiac group of preaortic glands.
The Inferior Gastric Glands (lymphoglandulae gastricae inferiores; right gastroepiploic gland), four to seven in number,
lie between the two layers of the greater omentum along the pyloric half of the greater curvature of the stomach.
The Hepatic Glands (lymphoglandulae hepaticae), consist of the following groups: (a) hepatic, on the stem of the hepatic
artery, and extending upward along the common bile duct, between the two layers of the lesser omentum, as far as the porta
hepatis; the cystic gland, a member of this group, is placed near the neck of the gall-bladder; (b) subpyloric, four or five in
number, in close relation to the bifurcation of the gastroduodenal artery, in the angle between the superior and descending
parts of the duodenum; an outlying member of this group is sometimes found above the duodenum on the right gastric (pyloric) artery. The glands of the hepatic chain receive afferents from the stomach, duodenum, liver, gall-bladder, and pancreas; their efferents join the celiac group of preaortic glands.
The Pancreaticolienal Glands (lymphoglandulae pancreaticolienales; splenic glands) accompany the lienal (splenic) artery,
and are situated in relation to the posterior surface and upper border of the pancreas; one or two members of this group are
found in the gastrolienal ligament. Their afferents are derived from the stomach, spleen, and pancreas, their efferents join
the celiac group of preaortic glands.
The superior mesenteric glands may be divided into three principal groups: mesenteric, ileocolic, and mesocolic.
The Mesenteric Glands (lymphoglandulae mesentericae) lie between the layers of the mesentery. They vary from one
hundred to one hundred and fifty in number, and may be grouped into three sets, viz.: one lying close to the wall of the
small intestine, among the terminal twigs of the superior mesenteric artery; a second, in relation to the loops and primary
branches of the vessels; and a third along the trunk of the artery.
The Ileocolic glands, from ten to twenty in number, form a chain around the ileocolic artery, but show a tendency to subdivision into two groups, one near the duodenum and another on the lower part of the trunk of the artery. Where the vessel
divides into its terminal branches the chain is broken up into several groups, viz.: (a) ileal, in relation to the ileal branch of
the artery; (b) anterior ileocolic, usually of three glands, in the ileocolic fold, near the wall of the cecum; (c) posterior ileocolic, mostly placed in the angle between the ileum and the colon, but partly lying behind the cecum at its junction with
the ascending colon; (d) a single gland, between the layers of the mesenteriole of the vermiform process; (e) right colic,
along the medial side of the ascending colon.
The Mesocolic Glands (lymphoglandulae mesocolicae) are numerous, and lie between the layers of the transverse mesocolon, in close relation to the transverse colon; they are best developed in the neighborhood of the right and left colic flexures. One or two small glands are occasionally seen along the trunk of the right colic artery and others are found in relation
to the trunk and branches of the middle colic artery.
The superior mesenteric glands receive afferents from the jejunum, ileum, cecum, vermiform process, and the ascending
and transverse parts of the colon; their efferents pass to the preaortic glands.
The inferior mesenteric glands consist of: (a) small glands on the branches of the left colic and sigmoid arteries; (b) a
group in the sigmoid mesocolon, around the superior hemorrhoidal artery; and (c) a pararectal group in contact with the
muscular coat of the rectum. They drain the descending iliac and sigmoid parts of the colon and the upper part of the rectum; their efferents pass to the preaortic glands.
the Lymphatic Vessels of the Abdominal and Pelvic Viscera
The lymphatic vessels of the abdominal and pelvic viscera consist of (1) those of the subdiaphragmatic portion of the digestive tube and its associated glands, the liver and pancreas; (2) those of the spleen and suprarenal glands; (3) those of the
urinary organs; (4) those of the reproductive organs.
1. The lymphatic vessels of the subdiaphragmatic portion of the digestive tube are situated partly in the mucous membrane
and partly in the seromuscular coats, but as the former system drains into the latter, the two may be considered as one.
The Lymphatic Vessels of the Stomach are continuous at the cardiac orifice with those of the esophagus, and at the pylorus with those of the duodenum. They mainly follow the bloodvessels, and may be arranged in four sets. Those of the first
set accompany the branches of the left gastric artery, receiving tributaries from a large area on either surface of the stomach, and terminate in the superior gastric glands. Those of the second set drain the fundus and body of the stomach on the
left of a line drawn vertically from the esophagus; they accompany, more or less closely, the short gastric and left gastroepiploic arteries, and end in the pancreaticolienal glands. The vessels of the third set drain the right portion of the greater
curvature as far as the pyloric portion, and end in the inferior gastric glands, the efferents of which pass to the subpyloric
group. Those of the fourth set drain the pyloric portion and pass to the hepatic and subpyloric glands, and to the superior
gastric glands.
The Lymphatic Vessels of the Duodenum consist of an anterior and a posterior set, which open into a series of small pancreaticoduodenal glands on the anterior and posterior aspects of the groove between the head of the pancreas and the duodenum. The efferents of these glands run in two directions, upward to the hepatic glands and downward to the preaortic
glands around the origin of the superior mesenteric artery.
The Lymphatic Vessels of the Jejunum and Ileum are termed lacteals, from the milk-white fluid they contain during intestinal digestion. They run between the layers of the mesentery and enter the mesenteric glands, the efferents of which end in
the preaortic glands.
The Lymphatic Vessels of the Vermiform Process and Cecum are numerous, since in the wall of this process there is a
large amount of adenoid tissue. From the body and tail of the vermiform process eight to fifteen vessels ascend between the
layers of the mesenteriole, one or two being interrupted in the gland which lies between the layers of this peritoneal fold.
They unite to form three or four vessels, which end partly in the lower and partly in the upper glands of the ileocolic chain.
The vessels from the root of the vermiform process and from the cecum consist of an anterior and a posterior group. The
anterior vessels pass in front of the cecum, and end in the anterior ileocolic glands and in the upper and lower glands of the
ileocolic chain; the posterior vessels ascend over the back of the cecum and terminate in the posterior ileocolic glands and
in the lower glands of the ileocolic chain.
Lymphatic Vessels of the Colon. - The lymphatic vessels of the ascending and transverse parts of the colon finally end in
the mesenteric glands, after traversing the right colic and mesocolic glands. Those of the descending and iliac sigmoid parts
of the colon are interrupted by the small glands on the branches of the left colic and sigmoid arteries, and ultimately end in
the preaortic glands around the origin of the inferior mesenteric artery.
Lymphatic Vessels of the Anus, Anal Canal, and Rectum. - The lymphatics from the anus pass forward and end with those
of the integument of the perineum and scrotum in the superficial inguinal glands; those from the anal canal accompany the
middle and inferior hemorrhoidal arteries, and end in the hypogastric glands; while the vessels from the rectum traverse the
pararectal glands and pass to those in the sigmoid mesocolon; the efferents of the latter terminate in the preaortic glands
around the origin of the inferior mesenteric artery.
The Lymphatic Vessels of the Liver are divisible into two sets, superficial and deep. The former arise in the subperitoneal
areolar tissue over the entire surface of the organ, and may be grouped into (a) those on the convex surface, (b) those on the
inferior surface.
(a) On the convex surface: The vessels from the back part of this surface reach their terminal glands by three different
routes; the vessels of the middle set, five or six in number, pass through the vena-caval foramen in the diaphragm and end
in one or two glands which are situated around the terminal part of the inferior vena cava; a few vessels from the left side
pass backward toward the esophageal hiatus, and terminate in the paracardial group of superior gastric glands; the vessels
from the right side, one or two in number, run on the abdominal surface of the diaphragm, and, after crossing its right crus,
end in the preaortic glands which surround the origin of the celiac artery. From the portions of the right and left lobes adjacent to the falciform ligament, the lymphatic vessels converge to form two trunks, one of which accompanies the inferior
vena cava through the diaphragm, and ends in the glands around the terminal part of this vessel; the other runs downward
and forward, and, turning around the anterior sharp margin of the liver, accompanies the upper part of the ligamentum teres, and ends in the upper hepatic glands. From the anterior surface a few additional vessels turn around the anterior sharp
margin to reach the upper hepatic glands.
(b) On the inferior surface: The vessels from this surface mostly converge to the porta hepatis, and accompany the deep
lymphatics, emerging from the porta to the hepatic glands; one or two from the posterior parts of the right and caudate
lobes accompany the inferior vena cava through the diaphragm, and end in the glands around the terminal part of this vein.
The deep lymphatics converge to ascending and descending trunks. The ascending trunks accompany the hepatic veins
and pass through the diaphragm to end in the glands around the terminal part of the inferior vena cava. The descending
trunks emerge from the porta hepatis, and end in the hepatic glands.
The Lymphatic Vessels of the Gall-bladder pass to the hepatic glands in the porta hepatis; those of the common bile duct
to the hepatic glands alongside the duct and to the upper pancreaticoduodenal glands.
The Lymphatic Vessels of the Pancreas follow the course of its bloodvessels. Most of them enter the pancreaticolienal
glands, but some end in the pancreaticoduodenal glands, and others in the preaortic glands near the origin of the superior
mesenteric artery.
2. The lymphatic vessels of the spleen and suprarenal glands.
The Lymphatic Vessels of the Spleen, both superficial and deep, pass to the pancreaticolienal glands.
The Lymphatic Vessels of the Suprarenal Glands usually accompany the suprarenal veins, and end in the lateral aortic
glands; occasionally some of them pierce the crura of the diaphragm and end in the glands of the posterior mediastinum.
3. The lymphatic vessels of the urinary organs.
The Lymphatic Vessels of the Kidney form three plexuses: one in the substance of the kidney, a second beneath its fibrous
capsule, and a third in the perinephric fat; the second and third communicate freely with each other. The vessels from the
plexus in the kidney substance converge to form four or five trunks which issue at the hilum. Here they are joined by vessels from the plexus under the capsule, and, following the course of the renal vein, end in the lateral aortic glands. The perinephric plexus is drained directly into the upper lateral aortic glands.
The Lymphatic Vessels of the Ureter run in different directions. Those from its upper portion end partly in the efferent
vessels of the kidney and partly in the lateral aortic glands; those from the portion immediately above the brim of the lesser
pelvis are drained into the common iliac glands; while the vessels from the intrapelvic portion of the tube either join the
efferents from the bladder, or end in the hypogastric glands.
The Lymphatic Vessels of the Bladder originate in two plexuses, an intra- and an extramuscular, it being generally admitted that the mucous membrane is devoid of lymphatics. The efferent vessels are arranged in two groups, one from the anterior and another from the posterior surface of the bladder. The vessels from the anterior surface pass to the external iliac
glands, but in their course minute glands are situated. These minute glands are arranged in two groups, an anterior vesical,
in front of the bladder, and a lateral vesical, in relation to the lateral umbilical ligament. The vessels from the posterior surface pass to the hypogastric, external, and common iliac glands; those draining the upper part of this surface traverse the
lateral vesical glands.
The Lymphatic Vessels of the Prostate terminate chiefly in the hypogastric and sacral glands, but one trunk from the posterior surface ends in the external iliac glands, and another from the anterior surface joins the vessels which drain the membranous part of the urethra.
Lymphatic Vessels of the Urethra. - The lymphatics of the cavernous portion of the urethra accompany those of the glans
penis, and terminate with them in the deep subinguinal and external iliac glands. Those of the membranous and prostatic
portions, and those of the whole urethra in the female, pass to the hypogastric glands.
(4) The lymphatic vessels of the reproductive organs.
The Lymphatic Vessels of the Testes consist of two sets, superficial and deep, the former commencing on the surface of
the tunica vaginalis, the latter in the epididymis and body of the testis. They form from four to eight collecting trunks which
ascend with the spermatic veins in the spermatic cord and along the front of the Psoas major to the level where the spermatic vessels cross the ureter and end in the lateral and preaortic groups of lumbar glands.
The Lymphatic Vessels of the Ductus Deferens pass to the external iliac glands; those of the vesiculae seminales partly to
the hypogastric and partly to the external glands.
The Lymphatic Vessels of the Ovary are similar to those of the testis, and ascend with the ovarian artery to the lateral and
preaortic glands.
The Lymphatic Vessels of the Uterine Tube pass partly with those of the ovary and partly with those of the uterus.
The Lymphatic Vessels of the Uterus consist of two sets, superficial and deep, the former being placed beneath the peritoneum, the latter in the substance of the organ. The lymphatics of the cervix uteri run in three directions: transversely to the
external iliac glands, postero-laterally to the hypogastric glands, and posteriorly to the common iliac glands. The majority
of the vessels of the body and fundus of the uterus pass lateralward in the broad ligaments, and are continued up with the
ovarian vessels to the lateral and preaortic glands; a few, however, run to the external iliac glands, and one or two to the
superficial inguinal glands. In the unimpregnated uterus the lymphatic vessels are very small, but during gestation they are
greatly enlarged.
The Lymphatic Vessels of the Vagina are carried in three directions: those of the upper part of the vagina to the external
iliac glands, those of the middle part to the hypogastric glands, and those of the lower part to the common iliac glands. On
the course of the vessels from the middle and lower parts small glands are situated. Some lymphatic vessels from the lower
part of the vagina join those of the vulva and pass to the superficial inguinal glands. The lymphatics of the vagina anastomose with those of the cervix uteri, vulva, and rectum, but not with those of the bladder.
The lymph glands of the thorax may be divided into parietal and visceral - the former being situated in the thoracic wall,
the latter in relation to the viscera.
The parietal lymph glands include the sternal, intercostal, and diaphragmatic glands.
1. The Sternal Glands (lymphoglandulae sternales; internal mammary glands) are placed at the anterior ends of the intercostal spaces, by the side of the internal mammary artery. They derive afferents from the mamma, from the deeper structures of the anterior abdominal wall above the level of the umbilicus, from the upper surface of the liver through a small
group of glands which lie behind the xiphoid process, and from the deeper parts of the anterior portion of the thoracic wall.
Their efferents usually unite to form a single trunk on either side; this may open directly into the junction of the internal
jugular and subclavian veins, or that of the right side may join the right subclavian trunk, and that of the left the thoracic
duct.
2. The Intercostal Glands (lymphoglandulae intercostales) occupy the posterior parts of the intercostal spaces, in relation
to the intercostal vessels. They receive the deep lymphatics from the postero lateral aspect of the chest; some of these vessels are interrupted by small lateral intercostal glands. The efferents of the glands in the lower four or five spaces unite to
form a trunk, which descends and opens either into the cisterna chyli or into the commencement of the thoracic duct. The
efferents of the glands in the upper spaces of the left side end in the thoracic duct; those of the corresponding right spaces,
in the right lymphatic duct.
3. The Diaphragmatic Glands lie on the thoracic aspect of the diaphragm, and consist of three sets, anterior, middle, and
posterior.
The anterior set comprises (a) two or three small glands behind the base of the xiphoid process, which receive afferents
from the convex surface of the liver, and (b) one or two glands on either side near the junction of the seventh rib with its
cartilage, which receive lymphatic vessels from the front part of the diaphragm. The efferent vessels of the anterior set pass
to the sternal glands.
The middle set consists of two or three glands on either side close to where the phrenic nerves enter the diaphragm. On the
right side some of the glands of this group lie within the fibrous sac of the pericardium, on the front of the termination of
the inferior vena cava. The afferents of this set are derived from the middle part of the diaphragm, those on the right side
also receiving afferents from the convex surface of the liver. Their efferents pass to the posterior mediastinal glands.
The posterior set consists of a few glands situated on the back of the crura of the diaphragm, and connected on the one
hand with the lumbar glands and on the other with the posterior mediastinal glands.
The superficial lymphatic vessels of the thoracic wall ramify beneath the skin and converge to the axillary glands. Those
over the Trapezius and Latissimus dorsi run forward and unite to form about ten or twelve trunks which end in the subscapular group. Those over the pectoral region, including the vessels from the skin covering the peripheral part of the
mamma, run backward, and those over the Serratus anterior upward, to the pectoral group. Others near the lateral margin of
the sternum pass inward between the rib cartilages and end in the sternal glands, while the vessels of opposite sides anastomose across the front of the sternum. A few vessels from the upper part of the pectoral region ascend over the clavicle to
the supraclavicular group of cervical glands.
The Lymphatic Vessels of the Mamma originate in a plexus in the interlobular spaces and on the walls of the galactophorous ducts. Those from the central part of the gland pass to an intricate plexus situated beneath the areola, a plexus
which receives also the lymphatics from the skin over the central part of the gland and those from the areola and nipple. Its
efferents are collected into two trunks which pass to the pectoral group of axillary glands. The vessels which drain the medial part of the mamma pierce the thoracic wall and end in the sternal glands, while a vessel has occasionally been seen to
emerge from the upper part of the mamma and, piercing the Pectoralis major, terminate in the subclavicular glands.
The deep lymphatic vessels of the thoracic wall consist of:
1. The lymphatics of the muscles which lie on the ribs: most of these end in the axillary glands, but some from the Pectoralis major pass to the sternal glands. 2. The intercostal vessels which drain the Intercostales and parietal pleura. Those
draining the Intercostales externi run backward and, after receiving the vessels which accompany the posterior branches of
the intercostal arteries, end in the intercostal glands. Those of the Intercostales interni and parietal pleura consist of a single
trunk in each space. These trunks run forward in the subpleural tissue and the upper six open separately into the sternal
glands or into the vessels which unite them; those of the lower spaces unite to form a single trunk which terminates in the
lowest of the sternal glands. 3. The lymphatic vessels of the diaphragm, which form two plexuses, one on its thoracic and
another on its abdominal surface. These plexuses anastomose freely with each other, and are best marked on the parts covered respectively by the pleurae and peritoneum. That on the thoracic surface communicates with the lymphatics of the
costal and mediastinal parts of the pleura, and its efferents consist of three groups: (a) anterior, passing to the gland which
lie near the junction of the seventh rib with its cartilage; (b) middle, to the glands on the esophagus and to those around the
termination of the inferior vena cava; and (c) posterior, to the glands which surround the aorta at the point where this vessel
leaves the thoracic cavity.
The plexus on the abdominal surface is composed of fine vessels, and anastomoses with the lymphatics of the liver and, at
the periphery of the diaphragm, with those of the subperitoneal tissue. The efferents from the right half of this plexus terminate partly in a group of glands on the trunk of the corresponding inferior phrenic artery, while others end in the right
lateral aortic glands. Those from the left half of the plexus pass to the pre- and lateral aortic glands and to the glands on the
terminal portion of the esophagus.
The visceral lymph glands consist of three groups, viz.: anterior mediastinal, posterior mediastinal, and tracheobronchial.
The Anterior Mediastinal Glands (lymphoglandulae mediastinales anteriores) are placed in the anterior part of the superior
mediastinal cavity, in front of the aortic arch and in relation to the innominate veins and the large arterial trunks which arise
from the aortic arch. They receive afferents from the thymus and pericardium, and from the sternal glands; their efferents
unite with those of the tracheobronchial glands, to form the right and left bronchomediastinal trunks.
The Posterior Mediastinal Glands (lymphoglandulae mediastinales posteriores) lie behind the pericardium in relation to
the esophagus and descending thoracic aorta. Their afferents are derived from the esophagus, the posterior part of the pericardium, the diaphragm, and the convex surface of the liver. Their efferents mostly end in the thoracic duct, but some join
the tracheobronchial glands.
The Tracheobronchial Glands form four main groups: (a) tracheal, on either side of the trachea; (b) bronchial, in the angles between the lower part of the trachea and bronchi and in the angle between the two bronchi; (c) bronchopulmonary, in
the hilus of each lung; and (d) pulmonary, in the lung substance, on the larger branches of the bronchi. The afferents of the
tracheobronchial glands drain the lungs and bronchi, the thoracic part of the trachea and the heart; some of the efferents of
the posterior mediastinal glands also end in this group. Their efferent vessels ascend upon the trachea and unite with efferents of the internal mammary and anterior mediastinal glands to form the right and left bronchomediastinal trunks. The
right bronchomediastinal trunk may join the right lymphatic duct, and the left the thoracic duct, but more frequently they
open independently of these ducts into the junction of the internal jugular and subclavian veins of their own side.
In all town dwellers there are continually being swept into these glands from the bronchi and alveoli large quantities of the
dust and black carbonaceous pigment that are so freely inhaled in cities. At first the glands are moderately enlarged, firm,
inky black, and gritty on section; later they enlarge still further, often becoming fibrous from the irritation set up by the
minute foreign bodies with which they are crammed, and may break down into a soft slimy mass or may calcify.
The lymphatic vessels of the thoracic viscera comprise those of the heart and pericardium, lungs and pleura, thymus, and
esophagus.
The Lymphatic Vessels of the Heart consist of two plexuses: (a) deep, immediately under the endocardium; and (b) superficial, subjacent to the visceral pericardium. The deep plexus opens into the superficial, the efferents of which form right
and left collecting trunks. The left trunks, two or three in number, ascend in the anterior longitudinal sulcus, receiving, in
their course, vessels from both ventricles. On reaching the coronary sulcus they are joined by a large trunk from the diaphragmatic surface of the heart, and then unite to form a single vessel which ascends between the pulmonary artery and the
left atrium and ends in one of the tracheobronchial glands. The right trunk receives its afferents from the right atrium and
from the right border and diaphragmatic surface of the right ventricle. It ascends in the posterior longitudinal sulcus and
then runs forward in the coronary sulcus, and passes up behind the pulmonary artery, to end in one of the tracheobronchial
glands.
The Lymphatic Vessels of the Lungs originate in two plexuses, a superficial and a deep. The superficial plexus is placed
beneath the pulmonary pleura. The deep accompanies the branches of the pulmonary vessels and the ramifications of the
bronchi. In the case of the larger bronchi the deep plexus consists of two net-works - one, submucous, beneath the mucous
membrane, and another, peribronchial, outside the walls of the bronchi. In the smaller bronchi there is but a single plexus,
which extends as far as the bronchioles, but fails to reach the alveoli, in the walls of which there are no traces of lymphatic
vessels. The superficial efferents turn around the borders of the lungs and the margins of their fissures, and converge to end
in some glands situated at the hilus; the deep efferents are conducted to the hilus along the pulmonary vessels and bronchi,
and end in the tracheobronchial glands. Little or no anastomosis occurs between the superficial and deep lymphatics of the
lungs, except in the region of the hilus.
The Lymphatic Vessels of the Pleura consist of two sets - one in the visceral and another in the parietal part of the membrane. Those of the visceral pleura drain into the superficial efferents of the lung, while the lymphatics of the parietal pleura
have three modes of ending, viz.: (a) those of the costal portion join the lymphatics of the Intercostales interni and so reach
the sternal glands; (b) those of the diaphragmatic part are drained by the efferents of the diaphragm; while (c) those of the
mediastinal portion terminate in the posterior mediastinal glands.
The Lymphatic Vessels of the Thymus end in the anterior mediastinal, tracheobronchial, and sternal glands.
The Lymphatic Vessels of the Esophagus form a plexus around that tube, and the collecting vessels from the plexus drain
into the posterior mediastinal glands.
Practice skills
Students are supposed to give name and identify the mentioned anatomical structures on samples
Practice class 36. Review: vessels and nerves of thorax.
Practice class 37. Review: vessels and nerves of abdomen.
Practice class 38. Review: vessels and nerves of pelvis. Examination of self-taught tasks.
Practice class 39. Tutorial of module 2. Examination of self-taught tasks.
Practice class 40. Written tests and examination of practice skills on nerves and vessels of internal organs and body cavities.