OBJECTIVES EXAM 4
Scalp, Cranial Cavity, Meninges & Brain:
 Define the scalp, its structural layers, muscles, nerves, and vessels.
 Identify the prominent landmarks on the internal surface of the skull base.
 Identify the major blood vessels of the brain, the specializations of cranial
meninges, and cranial dural modifications.
 Identify the cranial nerves on the brain and their courses through the skull base.
 Identify the parts of the ventricular system and trace the flow of cerebrospinal
fluid from production to reabsorption.
Parotid Gland & Face:
 Identify three main neurovascular structures that traverse the parotid gland: the
facial nerve, the retromandibular vein and external carotid artery.
 Identify the branches of the facial nerve in the face.
 Identify muscles of facial expression and nerve supply.
 Describe blood supply to the face.
 Describe cutaneous nerve supply to the head and face.
Eye:




Describe the components of the eyelids with associated muscles, tarsal glands,
connective tissue fascia and conjunctiva.
Identify the extraocular and intraocular muscles, their function and innervation.
Identify all sensory, motor and autonomic nerves of the orbit and trace their
routes to and within the orbit.
Identify branches of ophthalmic arteries and veins.
Ear & Nasal Cavity:
 Define the three parts of the ear and the function of each part.
 Describe each of the four walls of the middle.
 Describe the structure and actions of the tympanic membrane, the auditory
ossicles, and the muscles of the middle ear.
 Trace the course of the facial nerve through the temporal bone and give the
origin, course, and functional components of each of its intracranial branches.
 Identify the auditory tube and explain its function.
 Describe the maxillary nerve, its distribution and functional significance.
 Describe the nasal cavity, openings, nasal septum, conchae, meatuses, and its
general neurovascular supply.
 List the paranasal sinuses and where each opens into the nasal cavity.
 Describe the hard and soft palate.
Infratemporal Fossa & Oral Cavity:
 Identify the masticatory muscles and give their functions.
 Define the boundaries and contents of the infratemporal fossa.
 Identify the branches of the trigeminal nerve and their functions related to
mastication and sensation from the face.
 Identify the chorda tympani nerve and give its function.
 Describe the structure and function of the temporomandibular joint.
 Describe the submandibular and sublingual salivary glands and give their
innervations.
 List the muscles of the tongue and their innervation.
 Describe the oral cavity, its oral vestibule and dental arches, and the hard and
soft palate.
Anterior Triangle:
 Identify and list the attachments, innervation and action of the
sternocleidomastoid, digastric and infrahyoid (strap) muscles.
 Identify the boundaries of the anterior and posterior cervical triangles and their
subdivisions.
 Describe the cutaneous branches of the cervical plexus and identify their areas
of distribution.
 Identify the deep cervical fascia, its various component layers and the resulting
compartmentalization of the neck.
 Locate and describe the specific features of the thyroid gland.
 Give the position of the parathyroid glands and consider the thyroid/parathyroid
gland relationship in terms of vascular supply and surgical intervention.
 Recognize and describe the contents of the carotid sheath and their relationships
with surrounding structures.
 Locate the vagus nerve and give its relationships to the fascia, vessels and
viscera of the region.
Posterior Triangle:
 Identify the boundaries of the posterior cervical triangle and its subdivisions.
 Identify the scalene muscles and the first rib and relate them to the
neurovascular structures at the root of the neck.
 Identify and list the parts and branches of the subclavian artery and vein, and
describe their course in the neck.
 Identify the neurovascular entities that have different relationships to structures
on the right and left sides of the root of the neck.
 In the root of the neck, locate the vagus and phrenic nerves and describe their
relationships to the organs, fascia, vessels, and viscera of the neck.
 Identify the deep cervical lymph nodes and explain their significance.
Viscera of Neck (Carotid Sheath, Pharynx, & Larynx):
 Review the arrangement, distribution and function of the cervical sympathetic
trunk.
 Review the carotid sheath and contents.
 Identify, trace and describe the general functions of cranial nerves IX
(glossopharyngeal), X (vagus), XI (spinal accessory), XII (hypoglossal).
 Describe the pharynx, its anatomical architecture and action of its musculature
during swallowing.
 List the basic functions of the larynx.
 Identify the main cartilages and membranes that form the internal framework
(skeleton) of the larynx.
 Describe the actions of the intrinsic muscles of the larynx in tensing, relaxing,
abducting or adducting the vocal folds.
 Describe the innervation and vascular supply of the larynx.
Cranial Nerves:
 List cranial nerves, Indentify origin and course of each nerve
 List functional components of each nerve and their innervation
 Identify the branches of each cranial nerve
 List parasympathetic ganglia and cranial nerves related to them (pre synaptic &
post- synaptic)
 Identify clinical conditions related to specific cranial nerve injuries
Learning Objectives and Explanations:
1. Identify and list the attachments, innervation and action of the sternocleidomastoid
muscle and infrahyoid (strap) muscles. (N 27,28,29,31, TG 7-12, 7-13, 7-16)
The names of these muscles are helpful in identifying their locations. For example:
"omo" means shoulder, and omohyoid goes from the shoulder to the hyoid bone.
Muscles
Origin
Insertion
Innervation
Action
Omohyoid
Inferior
belly: upper
border of
scapula
medial to
scapular
notch
Superior
belly:
intermediate
tendon
Superior
Ansa cervicalis
belly: lower
border of
hyoid lateral
to
sternohyoid
insertion
Inferior
belly:
intermediate
tendon
Depresses/stabilizes
hyoid bone
Sternohyoid
Posterior
surfaces of
manubrium
and sternal
end of
clavicle
Lower border Ansa cervicalis
of hyoid
bone, medial
to omohyoid
insertion
Depresses/stabilizes
hyoid bone
Sternothyroid
Posterior
surface of
manubrium
below
sternohyoid
origin
Oblique line Ansa cervicalis
of thyroid
cartilage
Depresses/stabilizes
thyroid cartilage
Thyrohyoid
Oblique line Lower border Ansa cervicalis Elevates larynx;
of thyroid
of hyoid bone (via fibers
Depresses/stabilizes
cartilage
running with
hyoid bone
hypoglossal
nerve that leave
XII distal to the
superior limb of
ansa)
Sternocleidomastoid Sternal head:
anterior
surface of
manubrium;
Clavicular
head: medial
one-third of
clavicle
Mastoid
process and
lateral aspect
of superior
nuchal line
Spinal accessory
nerve (XI), with
sensory supply
from C2 & C3
(for
proprioception)
Draws mastoid
process down to
same side; turns
chin up toward
opposite side
2. Identify the boundaries of the anterior and posterior cervical triangles and their
subdivisions. (N 28, TG 7-02A, 7-02B)


Anterior cervical triangle
o boundaries:
 medial: midline
 lateral: anterior border of the sternocleidomastoid muscle
 superior: lower border of the mandible
o subdivisions:
 muscular triangle
 medial: midline
 superolateral: superior belly of the omohyoid muscle
 inferolateral: sternocleidomastoid muscle
 submandibular triangle
 anterior: anterior belly of the digastric muscle (this muscle
is not in this lab, so for now it is sufficient to know its
location as a reference for triangle borders).
 posterior: posterior belly of the digastric muscle
 superior: lower border of the mandible
 submental triangle
 lateral: anterior belly of digastric muscle
 medial: midline
 inferior: hyoid bone
 carotid triangle
 lateral: sternocleidomastoid muscle
 superior: posterior belly of the digastric muscle
 anterior: superior belly of the omohyoid muscle
Posterior cervical triangle
o boundaries:
 anterior: sternocleidomastoid muscle
 posterior: trapezius muscle
 inferior: clavicle
o subdivisions:
 subclavian/omoclavicular triangle
 superior: inferior belly of omohyoid muscle
 anterior: sternocleidomastoid muscle
 inferior: clavicle
 occipital triangle
 anterior: sternocleidomastoid muscle
 posterior: trapezius muscle
 inferior: omohyoid muscle
3. Describe the cutaneous branches of the cervical plexus and identify their areas of
distribution. (W & B 191 and Fig 190; N 24,31,32,129,178, TG 7-11, 7-16A,7-16B, 7-13)
The cutaneous branches of the cervical plexus include the lesser occipital, the great
auricular, the transverse cervical, and the supraclavicular nerves. They emerge along the
lateral border of the sternocleidomastoid muscle in the order of lesser occipital, great
auricular, transverse cervical, and supraclavicular (superior to inferior). (Note: Netter 31
incorrectly indicates that the great auricular is superior to the lesser occipital. The lesser
occipital comes from C2 and the great auricular comes from branches of C2 and C3.)
Nerve
Source
Lesser occipital C2
Location
Ascends in the neck along the posterior
border of the sternocleidomastoid muscle;
pierces the cervical fascia near the muscle
and divides into branches
Area of
distribution
Skin and
subcutaneous tissue
behind the ear
Great auricular C2, C3 Appears at the lateral border of the
Skin of the ear and
sternocleidomastoid muscle just below the below the ear
lesser occipital nerve and goes toward the
auricle and the angle of the mandible
Transverse
cervical
C2, C3 Appears below the great auricular nerve at Skin of the neck
the lateral border of the
anteriorly
sternocleidomastoid muscle; crosses the
muscle horizontally to reach the anterior
triangle deep to the platysma muscle and
the external jugular vein
Supraclavicular C3, C4 Emerges below the transverse cervical
nerve at the lateral edge of the
sternocleidomastoid muscle; descends
through the inferior part of the posterior
triangle and divides into three branches that
pierce the platysma near the clavicle
Skin of the root of
the neck; upper
chest and upper
shoulder anteriorly
4. Identify the deep cervical fascia, its various component layers and the resulting
compartmentalization of the neck. (W & B 191-195 and Fig 3-6, N 35, TG 7-10,7-11)
Deep cervical fascia components:





superficial (investing) layer: (Note: this is the superficial layer of the deep
fascia, which is different from superficial fascia) extends between the trapezius
and the sternocleidomastoid muscles in the posterior triangle and between the
paired sternocleidomastoid muscles in the anterior triangle. It surrounds all the
deeper parts of the neck and splits to enclose the trapezius and
sternocleidomastoid muscles. It also splits above the manubrium to create the
suprasternal space (the jugular venous arch connecting the anterior jugular veins
goes through this space).
infrahyoid (muscular) fascia: has a superficial layer which encloses the
sternohyoid and omohyoid muscles and a deeper lamina which encloses the
sternothyroid and thyrohyoid muscles. Both layers create a semi-circle on the
anterior side of the neck and end superiorly at the hyoid bone. Inferiorly they pass
behind the sternum onto the left brachiocephalic vein and the pericardium.
visceral fascia: encloses the pharynx, esophagus, larynx, trachea, thyroid, and
parathyroid glands. It has two components: pretracheal fascia anteriorly and the
buccopharyngeal fascia posteriorly.
carotid sheath: encloses the internal and common carotid arteries, internal
jugular vein, and vagus nerve.
prevertebral fascia: forms a complete enclosure of the cervical vertebrae and
their associated longitudinal musculature, vessels, and nerves. There are also
some interfascial spaces. The most important is the retropharyngeal space. This
space is between the buccopharyngeal and prevertebral fascias and accommodates
the movements of the pharynx and associated parts during swallowing.
5. Locate and describe the specific features of the thyroid gland. (W & B 197-8, N 74,
TG 7-13, 7-14)
The thyroid gland is H-shaped with lateral lobes making up the vertical lines and the
isthmus making up the middle bar. There also sometimes is a pyramidal lobe which
extends upward from the isthmus or from the junction of the isthmus and one of the
lateral lobes. The thyroid gland arches over the trachea and is bound posterolaterally by
the carotid sheath contents and anterolaterally by the sternothyroid muscles. The upper
parts of the lateral lobes are molded against the cricoid and thyroid cartilages.
6. Give the position of the parathyroid glands and consider the thyroid/parathyroid gland
relationship in terms of vascular supply and surgical intervention. (W & B 201; N 74, 75,
TG 7-14)
The parathyroid glands are usually four (but may be two to six) small glands lying
posterior (superior parathyroids) or inferior (inferior parathyroids) to the thyroid gland.
Blood supply comes from branches of the inferior or superior thyroid arteries, or from the
longitudinal anastomosis between these vessels. Venous drainage flows into the thyroid
plexus of veins. Inadvertent removal or damage of the parathyroid glands can occur in
surgery on the thyroid gland because of variable positions of the parathyroid glands. If
the parathyroid glands atrophy or are all removed during surgery, the patient suffers from
tetany, severe convulsive muscle spasms resulting from a fall in serum calcium levels.
7. Discuss the general features of endocrine system and specifically those of the thyroid
and parathyroid glands.
You will get much more on this in Physiology and Histology, but for now this summary
is sufficient.
Thyroid gland


composed of two populations of cells: follicles and the surrounding parafollicular
cells
produces two hormones
o calcitonin: lowers calcium and phosphate levels in the blood and is
regulated by serum calcium levels
o thyroxine: increases basal metabolic rate. Also feeds back to decrease
TSH and TRH synthesis and release from the pituitary and hypothalamus.
Parathyroid gland

produces parathyroid hormone - increases blood calcium levels (opposite of
calcitonin) and lowers phosphate levels (same as calcitonin). It is regulated by
serum calcium levels
8. Recognize and describe the contents of the carotid sheath and their relationships with
surrounding structures (below the level of the hyoid bone). (N 32, 33, TG 7-17, 7-18, 713)
The carotid sheath contains the internal and common carotid arteries, the internal jugular
vein, and the vagus nerve. Through the middle neck levels, the superior root of the ansa
cervicalis lies in the sheath anteriorly. The carotid sheath is posterolateral to the thyroid
gland and anterior to the prevertebral fascia. The sympathetic trunk lies behind the medial
portion of the sheath. (N 75, TG 7-14,7-15)
9. Locate the vagus nerve and give its relationships to the fascia, vessels and viscera of
the region. (W & B 201-3; N 32, 33, TG 7-13, 7-14)
The vagus nerve runs between and posterior to the common carotid artery and the internal
jugular vein in the carotid sheath (the artery is medial, the vein lateral). The rest of the
question is answered above.
Questions and Answers:
1. Are the external jugular, anterior jugular, jugular venous arch, and communicating
veins bilaterally symmetrical in arrangement or size? Are they all present?
These veins are quite variable and are often asymmetrical. It will be unlikely that you will
find all of them in one specimen. (N 31, 256, TG 7-11)
2. How does the innervation to the thyrohyoid muscle differ from the other strap
muscles?
Thyrohyoid innervation comes from C1 & C2 via the hypoglossal nerve, arising after the
superior root of the ansa cervicalis leaves the hypoglossal nerve. (N 32, 135, TG 7-13, 718)
3. Trauma to the external branch of the superior laryngeal nerve to the cricothyroid
muscle during thyroid surgery may result in changes in voice quality. Why?
Because cricothyroid muscle tenses the vocal cords by pulling the thyroid and cricoid
cartilages closer together anteriorly. (N 74,78, 126, TG 7-26, 7-18)
4. Is there a thyroidea ima artery present?
Only if your cadaver is in the lucky 10% containing this artery.
5. To what vessels do the middle and inferior thyroid veins drain?
Middle thyroid: internal jugular vein
Inferior thyroid: left and right brachiocephalic veins (N 74, TG 7-13)
Learning Objectives and Explanations:
1. Identify the boundaries of the posterior cervical triangle and its subdivisions. (WB 187,
3-1; N28, TG7-02A, TG7-02B)
Border: Formed by:
anterior posterior border of the sternocleidomastoid muscle (SCM)
posterior anterior border of the trapezius
inferior middle third of the clavicle between the trapezius and SCM
apex
where the SCM and trapezius meet on the superior nuchal line of the occiptal
bone
roof
superficial layer of deep cervical fascia
floor
formed by the levator scapulae, middle scalene, and posterior scalene, which
are all covered by the prevertebral layer of deep cervical fascia
The posterior cervical triangle is subdivided into the following triangles by the inferior
belly of the omohyoid muscle:


Occipital triangle, whose contents are:
o part of external jugular vein
o posterior branches of cervical plexus of nerves
o accessory nerve
o trunks of brachial plexus
o transverse cervical artery
o cervical lymph nodes
Subclavian triangle (aka omoclavicular), whose contents are:
o third part of subclavian artery
o part of subclavian vein
o suprascapular artery
o supraclavicular lymph nodes
2. Identify the scalene muscles and the first rib and relate them to the neurovascular
structures at the root of the neck. (N30, N32, N33, N186, N192, N194, N429, TG7-15A,
TG7-15B, TG7-17, TG7-18)
For orientation, it is good to know the origins and insertions of the scalenes relative to the
rib:



The anterior scalene muscle descends inferolaterally from the transverse
processes of C3 through C6 to the scalene tubercle on the 1st rib.
The middle scalene muscle descends inferolaterally from the transverse processes
of C2 through C7 to the upper surface of the 1st rib.
The posterior scalene muscle passes from the transverse process of C5 through C7
to the lateral surface of the 2nd rib.
Nerves and their relations to the scalene muscles and 1st rib:



The relation of the scalene muscles to nerves mainly occurs between the anterior
and middle scalene muscles. In the space between these two muscles, known as
the interscalene triangle:
o C3, C4, and C5 spinal nerves emerge and give off their contributions to
the phrenic nerve, which runs inferiorly on the anterior scalene muscle
o inferior to the three aforementioned spinal nerves, the roots of the brachial
plexus (C5 through T1) emerge as well
Another nerve that has a specific relation with the scalene muscles is the vagus
nerve while it is contained in the carotid sheath. Plates N31, N32, TG7-14, TG720 show the vagus nerve descending on the origin of the anterior scalene muscle.
Other relevant nerves are the dorsal scapular nerve and long thoracic nerve, both
of which pass through the middle scalene muscle after branching off of the roots
of the brachial plexus (C5 for dorsal scapular, C5-7 for long thoracic).
Arteries and veins and their relations to the scalenes and 1st rib:

The most important relations to notice are those of the subclavian artery and vein.
The subclavian arteries are separated from the veins by the anterior scalene

muscle, with the artery being posterior to the muscle and the vein anterior to it.
Both of these vessels start posterior to the sternoclavicular joint and parallel each
other as they pass inferior to the clavicle and superior to the 1st rib to become the
axillary artery/vein. Since both vessels rest on the 1st rib, there are grooves that
mark their positions on the rib.
As for the branches/tributaries of the subclavian artery/vein, three branches of the
thyrocervical trunk (1st part of subclavian) rest on the anterior scalene muscle as
they travel to their destinations. These branches are the transverse cervical artery,
suprascapular artery, and ascending cervical artery (actually a branch of inferior
thyroid artery, the third branch of the thyrocervical trunk). Veins parallel these
arteries and ultimately reach the subclavian vein. (N32, TG7-15A, TG7-15B)
3. Identify and list the parts and branches of the subclavian artery and vein, and describe
their course in the neck. (N33, N70, N74, N238, TG7-15A, TG7-15B)
The subclavian artery arises superiorly from the brachiocephalic trunk (right side) or the
aortic arch (left side) and travels between the anterior and middle scalene muscles. It then
travels inferiorly between the clavicle and first rib to enter the pectoral region, where it
becomes the axillary artery. The subclavian artery is divided into three parts by the
anterior scalene muscle (this is similar to the pectoralis minor dividing the axillary artery
into three parts):



The first part of the subclavian artery is medial to the anterior scalene muscle and
gives off the following branches:
o vertebral artery - the cervical part of the vertebral artery ascends just
medial to the muscles and passes deeply at its apex to course through the
foramina of the transverse processes of C1 through C6. The suboccipital
part of the vertebral artery courses in a groove on the posterior arch of the
atlas before it enters the cranial cavity through the foramen magnum.
o internal thoracic artery - arises from the anteroinferior aspect of the
subclavian artery and passes inferomedially into the thorax. The cervical
part of this artery has no branches.
o thyrocervical trunk - arises from the anterosuperior aspect of the first part
of the subclavian artery, just medial to the anterior scalene muscle, and has
three branches:
 inferior thyroid artery
 transverse cervical artery - sends branches to muscles in the
posterior cervical triangle, the trapezius, and medial scapular
muscles
 suprascapular artery
The second part of the subclavian artery is posterior to the anterior scalene muscle
and only has one branch:
o costocervical trunk - arises from the posterior aspect of the subclavian
artery. It passes posterosuperiorly and divides into:
 superior intercostal artery - supplies first two intercostal spaces
 deep cervical artery - supplies posterior deep cervical muscles
The third part of the subclavian artery is lateral to the anterior scalene muscle and
only has one branch:
o dorsal scapular artery - occasionally arises as a branch of the transverse
cervical artery. When it is a branch of the subclavian, it passes laterally
through the trunks of the brachial plexus, anterior to the middle scalene
muscle, and then runs deep to the levator scapulae to reach the scapula and
supply the rhomboid muscles.
The subclavian vein begins at the lateral border of the 1st rib as a continuation of the
axillary vein and ends when it unites with the IJV, posterior to the medial end of the
clavicle (SC joint). The important part of the subclavian vein is that when it meets the
IJV, it forms the brachiocephalic vein. This union is known as the venous angle and is the
site where the thoracic duct and right lymphatic duct drain their lymph into the venous
circulation. The subclavian vein receives the external jugular vein, anterior jugular vein,
and vertebral vein. The external jugular vein receives the suprascapular vein and the
transverse cervical vein. One thing to note is that even though the inferior thyroid
ARTERY is a branch of the thyrocervical trunk of the subclavian artery, the inferior
thyroid VEIN drains into the brachiocephalic vein, separate from the other branches of
the thyrocervical trunk, which drain into the subclavian vein.
4. Identify the neurovascular entities that have different relationships to structures on the
right and left sides of the root of the neck. (N32,N33,N75,N193,N237,N238,N240,N266,
TG4-18, TG4-38, TG4-44, TG7-14, TG7-15)
Vagus nerves - The vagus nerves pass anterior to the first part of the subclavian artery
and posterior to the brachiocephalic vein and SC joint to enter the thorax. (N31, N32,
TG7-13, TG4-45)
Recurrent laryngeal nerves - branches of the vagus nerves - The right recurrent laryngeal
nerve loops inferior to the right subclavian artery at approximately the T1 vertebral level.
The nerve then ascends in the tracheoesophageal groove to supply all the intrinsic
muscles of the larynx, except the cricothyroid (will need to know this later). To better
orient yourself, remember that the vagus nerve descends anterior to the subclavian artery
and posterior to the vein. The left recurrent laryngeal nerve loops inferior to the arch of
the aorta behind the ligamentum arteriosum at approximately the T4/T5 intervertebral
disc level. Recurrent nerve ascends in the tracheoesophageal groove to supply all the
intrinsic muscles of the larynx, except the cricothyroid (will need to know this later).
Brachiocephalic trunk - This vessel is only found on the right side of the body as it
branches into the right common carotid artery and the right subclavian artery. On the left
side, there is no brachiocephalic trunk since the left common carotid artery and left
subclavian artery directly branch off of the arch of the aorta.
Subclavian arteries - The right subclavian artery arises from the brachiocephalic trunk,
posterior to the right SC joint. The first part courses superolaterally, extending between
its origin and the medial margin of the anterior scalene muscle. The left subclavian artery
arises from the arch of the aorta, ascends through the superior mediastinum and enters the
root of the neck posterior to the left SC joint. The subclavian veins both end at their
respective SC joints by uniting with the internal jugular vein to form the brachiocephalic
veins. The left brachiocephalic vein is longer than the right because it needs to cross the
branches of the aortic arch to reach the right brachiocephalic to form SVC.
Common carotid arteries - The right common carotid artery branches off the
brachiocephalic trunk and ascends lateral to the trachea. The left common carotid artery
branches off of the aortic arch and then ascends lateral to the trachea, thus it is a little
longer than the right common carotid artery.
Lymphatic ducts - the right lymphatic duct usually drains to the union of the right
subclavian and right internal jugular veins. The thoracic duct wraps around the posterior
aspect of the left internal jugular vein before it comes around to drain lateral to the left
brachiocephalic vein. (Note: these are the only two lymphatic vessels large enough to be
called ducts. Everything else is either a lymph trunk or simply a lymph vessel.)
5. In the root of the neck, locate the vagus and phrenic nerves and describe their
relationships to the organs, fascia, vessels, and viscera of the neck. (WB 220; N32, N33,
TG7-13 TG7-14)
For a description of the vagus, see Objective 4. The phrenic nerve arises by a large root
from C4 and is reinforced by smaller contributions from C3 and C5. It passes out along
the lateral border of the anterior scalene muscle and enters the chest along its medial
border. It lies behind the prevertebral layer of deep cervical fascia and is crossed by the
transverse cervical and suprascapular vessels. At the root of the neck, the phrenic nerve
passes between the first portion of the subclavian vein and subclavian artery and in front
of the internal thoracic artery and vein.
6. Identify the deep cervical lymph nodes and explain their significance. (N72, N239,
N266, TG7-74)
The deep cervical nodes are mostly lateral and posterior to the IJV. The nodes are divided
into superior and inferior subgroups at the point where the omohyoid muscle crosses over
the IJV. Thus, those deep nodes above this crossing are the superior deep cervical lymph
nodes and those below the crossing are the inferior deep cervical lymph nodes. (WB 208)
Channels from the inferior deep cervical lymph nodes, also called supraclavicular nodes,
join to form the jugular lymphatic trunks, which usually join the thoracic duct on the left
side and the right lymphatic duct on the right side (sometimes it will enter the right
venous angle directly).
Questions and Answers:
7. At what foramen on the base of the skull does the internal jugular vein originate?
The internal jugular vein originates at the jugular foramen. (N8, TG7-06)
8. Can you identify the middle cervical ganglion?
This is occasionally absent. When present, it will lie near the level of the inferior thyroid
artery and the cricoid cartilage and the transverse process of C6, just anterior to the
vertebral artery. (N130, TG7-15)
9 Organize those parts of the cervical sympathetic trunk you have seen so far.
Inferior cervical ganglion - In approximately 80% of people, it fuses with the 1st thoracic
ganglion to form the large stellate ganglion (a.k.a. cervicothoracic ganglion). It lies
anterior to the transverse process of C7and the neck of the 1st rib on each side and
posterior to the origin of the vertebral artery.
Middle cervical ganglion - This is occasionally absent. It lies near the inferior thyroid
artery at the level of the cricoid cartilage and the transverse process of C6, just anterior to
the vertebral artery.
Superior cervical ganglion - This is a huge ganglion that can be confused with the nodose
ganglion of the vagus. This is found at the level of C1 and C2. (N130, N208, TG7-15,
TG7-95)
10. Do you see connections (gray rami communicantes) between the trunk or ganglia and
spinal nerves?
Yes, but you may NOT see any white rami communicantes because those are only
present from T1 through L2. One white ramus reaches the stellate ganglion, only. (N130,
TG7-15, TG7-95)
11. Are these (transverse cervical and suprascapular arteries) individual arteries or are
they derived from a common trunk?
Both of these arteries should be branches of the thyrocervical trunk which is a branch of
the first part of the subclavian artery. Sometimes they arise as a common trunk.
Suprascapular vessels travel laterally immediately behind the clavicle, while the
transverse cervical arches higher across the posterior triangle. (N33, TG7-15A, TG715B)
12. Study its (thyroid gland) relation to the sympathetic trunk and middle cervical
ganglion.
The thyroid gland as a whole will be anteromedial to the sympathetic trunk as it ascends
on the longus colli muscle. The inferior aspect of the thyroid gland should be just medial
to the middle cervical ganglion. (N39, N130, TG7-14)
13. Define the interscalene triangle.
The interscalene triangle is defined as the area between the posterior border of the
anterior scalene muscle, anterior border of the middle scalene muscle, and the superior
border of the 1st rib. The major structures that are located in this structure are the trunks
of the brachial plexus. (N34, TG7-15)
14. In forced inspiration, what muscle raises the second rib?
The posterior scalene muscle, since it inserts onto the second rib. Anterior and middle
scalene muscles would effectively raise the second rib also, however they insert on the
first rib. (N34, N186, TG7-15)
Learning Objectives and Explanations:
1. Review the arrangement, distribution and function of the cervical sympathetic trunk.
(WB 211-12; N 35, 128, 130, 131, 209, TG 7-10, 7-15, 7-95)
The left and right cervical sympathetic trunks:
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are a continuation of the thoracic sympathetic trunks
lie behind and medial to the carotid sheath and in front of prevertebral muscles
may be a solid trunk or strands connecting 2 or 3 cervical ganglia
cervical ganglia represent consolidation of the original 1 ganglion per cervical
spinal nerve, which is the pattern in the thorax. This consolidation of ganglia
happens in areas where there are gray rami but no white rami, such as above T1 or
below L2.
there are only gray rami communicantes between the cervical trunk and spinal
nerves C1-C8, because the highest level for white rami is T1. This means that all
of the preganglionic fibers of the cervical sympathetic trunk originated at T1 or
below (generally T1-T5). Postganglionic fibers in the cervical sympathetic trunk
originate from one of the three cervical ganglia (or thoracic ganglia).
much of the sympathetic innervation of the deep structures of the head occurs via
perivascular sympathetic nerve plexuses that follow branches of the external and
internal carotid arteries.
The superior cervical ganglion sends gray rami to C1-C4 spinal nerves (variable) and also
gives off other branches. It lies opposite the transverse process of C2. Besides the gray
rami to the spinal nerves, branches of the ganglion include:
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external carotid nerve reaches external carotid artery to form the external carotid
plexus. These perivascular fibers follow branches of the external carotid to all the
structures it supplies. For example, parotid gland sympathetic innervation comes
via the perivascular external carotid plexus (vasoconstriction reduces salivation).
internal carotid nerve, forming the perivascular internal carotid plexus to the
brain, orbit, and forehead.
branches to the carotid body.
superior cervical cardiac nerve (accelerates heart rate and increases force of
contraction).
sympathetic contributions to glossopharyngeal (CN IX), vagus (CN X), and
hypoglossal (CN XII) nerves.
branches to join the pharyngeal plexus (along with glossopharyngeal and vagus).
The middle cervical ganglion (which may be absent) sends gray rami to C5-6 spinal
nerves. It is at the level of the cricoid cartilage, often close to where the inferior thyroid
artery crosses the sympathetic trunk. Besides the gray rami, branches include:

middle cervical cardiac nerve, which has cardioaccelerator fibers, visceral afferent
fibers to the heart, and fibers that go to the thyroid.
The cervicothoracic or stellate ganglion, the fusion of the inferior cervical and first
thoracic ganglia, sends gray rami to C6,7,8 and T1. It lies anterior to the transverse
process of C7 or the head of rib 1. Its other name, stellate ganglion, comes from the fact
that its multiple branches spread out like light rays from a star. Branches include:
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inferior cervical cardiac n.
perivascular fibers to vertebral a. and from there into the brain, onto basilar,
posterior cerebral, and cerebellar aa.
the ansa subclavia is a superficial strand that loops down from the middle cervical
ganglion anteriorly around the subclavian artery and joins the inferior cervical
ganglion behind the artery.
this ganglion also receives a white ramus from T1.
Functions of the cervical sympathetic trunk:
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recall that sympathetic nerves cause vasoconstriction, secretion (sweat glands),
pilomotor functions, and contraction of smooth muscle. Vasoconstriction can
reduce output of glands like parotid by reducing blood flowing in. Specifically,
the cervical sympathetic trunk controls:
vasoconstriction of all the blood vessels of the brain and head (perivascular fibers)
blood vessels to salivary glands and other oral glands (external carotid n.)
acceleration of heart rate and strength of cardiac contraction through superior,
middle, and inferior cervical cardiac nerves
innervation of hair muscles and sweat glands on the head
innervation of dilatator pupillae m. of the eye and superior tarsal m. of the eyelid.
(Think about the eyes going wide with fright, a sympathetic-stimulating emotion.)
Horner's syndrome involves a lesion of the sympathetic trunk. Two of the more
noticeable signs of this syndrome are constriction of the pupil and slight ptosis (drooping)
of the eyelid.
2. Review the carotid sheath and contents. (WB 201,203,206; N 32, 33, 35, 125, 126, TG
7-17, 7-18, 7-13, 7-10)
The carotid sheath is a tube-shaped fascia wrapping the common carotid a., internal
carotid a., internal jugular v., and vagus n. It lies anterolateral to the cervical sympathetic
trunk, behind the sternocleidomastoid muscle. The sheath blends with the thyroid fascia
anteromedially and with the deep surface of sternocleidomastoid anterolaterally.
Posteriorly it is attached to prevertebral fascia along the tips of the transverse processes
of vertebrae. It ends at the base of the skull where it attaches around the jugular foramen
and carotid canal. It is here at the base of the skull that the internal carotid artery and
internal jugular vein go their separate ways. Inferiorly, the carotid sheath fuses with
scalene fascia, adventitia of great vessels, and the fibrous pericardium.
Within the sheath, artery is medial, vein lateral, and nerve posterior and between the
vessels.
The superior root of ansa cervicalis (from cervical plexus C1-2) lies draped over the
anterior part of the carotid sheath.
The carotid sinus is the dilated terminal part of the common carotid artery, approx. 1 cm
long. It is a baroreceptor in the elastic wall which responds to changes in blood pressure.
The carotid sinus is innervated by a branch of the glossopharyngeal nerve.
The carotid body is an disc-shaped mass lying behind the bifurcation of the common
carotid artery. It has a chemoreceptor sensitive to blood oxygen concentration. The
carotid body is innervated by the nerve to carotid sinus from glossopharyngeal nerve, and
also receives the nerve to carotid body, a branch of the vagus n. (CN X), as well as
sympathetic fibers.
3. Identify, trace and describe the general functions of cranial nerves IX
(glossopharyngeal), X (vagus), XI (spinal accessory), XII (hypoglossal). (WB
91,205,206,218,239; N 118, N125, 127, 128, TG 7-90, 7-91, 7-93, 7-94)
I
Olfactory
Some Sensory
II
Optic
Say
III
Oculomotor
Money Motor
IV
Trochlear
Matters Motor
V
Trigeminal
But
Both
VI
Abducens
My
Motor
VII Facial
Sensory
Brother Both
VIII Vestibulocochlear Says
Sensory
IX
Glossopharyngeal Big
Both
X
Vagus
Brains Both
XI
Accessory
Matter Motor
XII Hypoglossal
Most
Motor
Glossopharyngeal, CN IX, Both motor and sensory.
Emerges from medulla in the groove dorsal/lateral to the olive, passes through jugular
foramen, passes along the posterior border of stylopharyngeus m.
The short story:
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Motor: innvervates stylopharyngeus m. (that's the only muscle it innervates)
Sensory: posterior 1/3 of tongue: general sensory (pain, etc) and special sensory
(taste); sensory to pharynx via pharyngeal plexus
The long story . . . Branches include:
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Tympanic n. - parasympathetic fibers to otic ganglion, which supplies parotid
gland (increases salivation) and mucous membrane of the middle ear
Carotid sinus nerve, with branches to carotid sinus and carotid body
Pharyngeal branches which form the pharyngeal plexus (along with vagus and
cervical sympathetics)
Branches to stylopharyngeus (the ONLY motor branches of this nerve)
Branches to tonsils
Lingual branches - afferent fibers from the tongue report taste sensations and
somatic sensations from the posterior third of the tongue
Vagus, X, Both motor and sensory.
Arises from the medulla, in the groove dorsal and lateral to the olive, in the same plane as
glossopharyngeal (CN IX) and accessory (CN XI). The vagus leaves the skull through the
jugular foramen, descends through the neck in the carotid sheath behind and between the
internal carotid/common carotid and the internal jugular v.
The short story:
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Vagus supplies all the muscles of the pharynx and soft palate and upper 2/3rds of
esophagus EXCEPT stylopharyngeus (from glossopharyngeal) and tensor veli
palatini (from mandibular division of trigeminal V3). It does this primarily
through the pharyngeal plexus. The inferior pharyngeal constrictor is innervated
by the superior laryngeal external branch.
Vagus, through the superior and inferior laryngeal nerves, also supplies all
muscles and sensory innervation of the larynx.
Motor: The inferior laryngeals (=recurrent laryngeals) supply all the muscles of
the larynx EXCEPT cricothyroideus. Superior laryngeal external branch supplies
cricothyroideus.
Sensory: The inferior laryngeals supply sensory fibers to the larynx below the
vocal folds, but their role is minor in sensation. Superior laryngeal internal branch
supplies sensory fibers to the larynx above the vocal folds. It is the principal
sensory nerve of the larynx, according to W+B.
It also supplies fibers to the dura, trachea, heart, etc
The long story...
Branches include:
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meningeal to posterior dura mater
auricular to back of external ear
pharyngeal, which contribute to the pharyngeal plexus. The pharyngeal plexus
(from vagus, glossopharyngeal, and cervical symp trunk) supplies the constrictor
muscles
superior laryngeal n. Arises from the inferior ganglion of the vagus. Passes
inferomedially toward the larynx. Has 2 branches.
o internal branch: sensory to the mucous membrane of epiglottis
o external branch: inferior pharyngeal constrictor m., cricothyroid m.
cervical cardiac
recurrent laryngeal
o right recurrent laryngeal loops under and behind the subclavian a.
o left recurrent laryngeal loops under aortic arch
o both recurrent laryngeals ascend between the esophagus and trachea and
enter the larynx from under the inferior constrictor muscle. Above the
cricothyroid articulation, name changes to inferior laryngeal n.
o branches of the laryngeals include: cardiac, tracheal, esophageal,
pharyngeal branch to inferior pharyngeal constrictor m.
o inferior laryngeals innervate all intrinsic muscles of the larynx EXCEPT
cricothyroideus
Accessory, CN XI, Motor nerve.
Arises from rootlets of C1-C5 which ascend within the vertebral column through foramen
magnum. It then descends through the jugular foramen, where it receives fibers from the
cranial portion of the accessory nerve. Upon leaving through the jugular foramen, the
accessory nerve lies between the internal carotid and internal jugular veins. It travels
laterally, piercing and innervating sternocleidomastoid. It then passes through the muscle,
goes dorsally under the superficial layer of deep cervical fascia to trapezius, where it
joins sensory branches of C3 and C4 to form the subtrapezial plexus.
Hypoglossal, CN XII, Motor nerve.
Motor nerve of the tongue arises from the medulla oblongata in the anterolateral sulcus
between the pyramid and the olive. The rootlets which form the hypoglossal unite in the
hypoglossal canal. It emerges from the canal medial to carotid sheath, then goes lateral.
Travels for a short distance with the superior root of ansa cervicalis. Turns forward near
angle of the mandible, loops around occipital artery, enters the submandibular triangle
deep to posterior belly of digastric, and goes superior to the greater horn of the hyoid
bone. Terminal branches distribute to styloglossus, hyoglossus, genioglossus, and
intrinsic muscles of the tongue. Carries C1 and C2 fibers that leave as the superior root of
ansa cervicalis, and the nerves to the thyrohyoid and geniohyoid muscles.
4. Describe the pharynx, its anatomical architecture and action of its musculature during
swallowing. (WB 235; N 35, 63, 65, 66, 67, N125, 126, 130, TG 7-10A, 7-10B, 7-20, 721, 7-22, 7-24)
The pharynx is the multi-purpose chamber that connects the nasal and oral cavities
superiorly with the esophagus and larynx inferiorly. It is multi-purpose in that it is the
common pipe for food, liquids, and air, and it is the job of the pharynx to see that these
invaluable items travel through the right pipe to the proper destination.
The pharynx is the part of the digestive system posterior to the nasal and oral cavities,
extending posteriorly and inferiorly past the larynx. It extends to the inferior border of the
cricoid anteriorly and the inferior border of C6 posteriorly. The posterior wall of the
pharynx lies against the prevertebral layer of deep cervical fascia.
In the pharynx the paths of food and air cross. Food travels from the mouth (anterior) to
the esophagus (posterior). Air travels from the choanae (posterior) to the trachea
(anterior).
The interior of the pharynx is divided into 3 parts:
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nasopharynx, most superior, is behind the nasal cavity and superior to the soft
palate. It is strictly respiratory. Air enters the nasopharynx through the posterior
openings of the choanae, which are bisected by the posterior edge of the nasal
septum. At the upper posterior end of the nasopharynx is the pharyngeal tonsil,
which is lymphoid tissue known as adenoids when enlarged. The auditory tube to
the middle ear opens into the lateral wall of the nasopharynx. Its opening is
covered by the torus tubarius. The salpingopharyngeal fold is a vertical fold of
mucous membrane extending inferiorly from the opening of the auditory tube.
oropharynx, the middle portion of the pharynx, is posterior to the oral cavity and
connects with the nasopharynx above and the laryngopharynx below. The dorsum
of the tongue is anterior to the oropharynx. The inferior border of the oropharynx
is the epiglottis. Anteriorly it is continuous with the oral cavity at the
palatopharyngeal folds or arches.
laryngopharynx, the most inferior part of the pharynx, lies below the oropharynx
and posterior to the larynx. It extends from the epiglottis superiorly down to the
inferior border of the cricoid at C6. Its posterior and lateral walls are formed by
the middle and inferior pharyngeal constrictor muscles. Internally, the walls are
formed by palatopharyngeus and stylopharyngeus muscles. The laryngeal inlet
connects the laryngopharynx with the larynx. (Aside: Lateral to the laryngeal inlet
are the piriform recesses, where foreign bodies can become lodged.) The
laryngopharynx is continuous inferiorly with the esophagus.
Structure of the pharynx:
The wall of the pharynx is composed of two layers of 3 muscles each. The external rings
of circular constrictor muscles - the superior, middle, and inferior constrictors - contract
serially to push a bolus down to the esophagus. The internal ring of longitudinal muscles
- palatopharyngeus, stylopharyngeus, and salpingopharyngeus - elevate and widen the
pharynx to accommodate a bolus during swallowing. The fascia covering the outside of
the posterior of the pharynx is the buccopharyngeal fascia. The interior fascia is the
pharyngobasilar fascia.
Innervation of the pharynx:
Motor:
Pharynx muscles are innervated by branches from pharyngeal plexus with 2 exceptions:
stylopharyngeus (glossopharyngeal, CN IX) and tensor veli palatini (supplied by
mandibular division of trigeminal, V3). Other than these two exceptions, the vagus is the
source of motor innervation to the pharynx. The inferior pharyngeal constrictor also
receives innervation from the recurrent laryngeal and external branch of the superior
laryngeal (which are also derived from the vagus).
Sensory:
The glossopharyngeal sensory contribution to the pharyngeal plexus is connected to the
mucosa of all three parts of the pharynx. (Sensory nerve supply to the nasopharynx is
primarily from the maxillary division of trigeminal, V2)
The stages of swallowing (deglutition) (W+B 238)
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Bolus begins to move from the mouth into oropharynx by action of muscles of
tongue and soft palate. (voluntary)
The soft palate is elevated by the levator veli palatini and (to a lesser extent)
tensor veli palatini muscles to seal off the nasopharynx. (actions are involuntary
from here down)
The salpingopharyngeus muscle (one of the internal longitudinal pharyngeal
muscles) contracts drawing the lateral pharyngeal walls upward.
As the bolus moves into the back of the pharynx, the palatopharyngeus and
stylopharyngeus mm. (the other 2 longitudinal muscles) elevate the larynx and
pharynx causing the cavity to widen to receive the bolus.
After food passes the epiglottis, the superior, middle, and inferior pharyngeal
constrictors - all circular muscles - contract, one after the other, to push the bolus
into the esophagus.
5. List the basic functions of the larynx.
The larynx connects the superior pharynx (oro- and naso-) with the trachea. It is
specialized for producing voice, and a special part of the larynx - the epiglottis - protects
the airway during swallowing. To achieve these added functions, the larynx has
additional cartilages, muscles, ligaments, and mucous membranes.
6. Describe the anatomy of the interior of the larynx. (N 65, 66, 77, TG 7-22, 7-24, 7-27)
The laryngeal cavity extends superiorly from the laryngeal inlet at the border with the
laryngopharynx to the inferior border of the cricoid. It is covered with a mucous
membrane, which is continuous with the pharynx above and trachea below. It has three
parts.
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The inlet and vestibule of the larynx are above the vestibular (false vocal) folds.
The epiglottis, arytenoid cartilages, cuneiform and corniculate cartilages,
aryepiglottic folds, and piriform recesses are components here. Just below the
inlet is the widening called the vestibule, which ends below at the rima vestibuli,
the aperture between the false vocal folds. The lateral walls of the vestibule are
formed by the quadrangular membranes. The free inferior margins of the
quadrangular membranes form the vestibular folds (or false vocal folds). The rima
vestibuli, the opening between the vestibular folds, is wider than the rima glottidis
or glottis, the space between the true vocal folds, below.
The ventricle of the larynx is a cavity just below the vestibular folds and just
superior to the true vocal folds. The ventricle functions as a resonance chamber.
The infraglottic cavity extends from the glottis - the space between the vocal folds
- to the beginning of the trachea below. The true vocal folds, at the superior end of
the infraglottic cavity, are two mucous-membrane-covered vocal ligaments
stretched between the vocal processes of arytenoids and the deep surface of the
anterior angle of the thyroid cartilage. Vocalis and thyroarytenoid muscles lie
lateral, parallel, and adjacent to the vocal ligaments. These are the parts of the
larynx directly involved in making sound.
7. Identify the main cartilages and membranes that form the internal framework
(skeleton) of the larynx. (N 78A, 78B, 78C, 78D, 78E, TG 7-25, 7-28, 7-26, 7-27)
The larynx has nine cartilages (three unpaired and three paired):
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Thyroid cartilage - largest, unpaired. Extends laterally but is not continuous
posteriorly, so it doesn't form a complete ring around the airway. Is composed of
two quadrilateral laminae fused together in the anterior midline where there is a
dip called the superior thyroid notch. This dip projects anteriorly to form the
laryngeal prominence (Adam's apple). Along the lateral margins of the cartilage
are the oblique lines running from the superior to inferior tubercles. The oblique
line provides a point of attachment for the sternothyroid and thyrohyoid muscles
anteriorly and the inferior pharyngeal constrictor muscle posteriorly. The superior
border of the thyroid cartilage attaches to the hyoid bone by the thyrohyoid
membrane. Inferior horns of the thyroid cartilage articulate with the lateral surface
of the cricoid at the cricothyroid joints. The interior of the thyroid cartilage is
covered by the mucous membrane of the interior of the larynx. The interior part of
the thyroid cartilage deep to the superior notch is the point of attachment for the
stem of the epiglottis, the vocal and vestibular ligaments, and three muscles:
thyroarytenoid and its thyroepiglottic and vocalis parts.
Cricoid cartilage - is an unpaired signet-ring-shaped cartilage with the narrow
band (the arch) facing anteriorly and the broadened signet portion (the lamina)
facing posteriorly. The cricoid is the only complete ring of cartilage to encircle
the airway. Cricoid attaches to the thyroid cartilage by the median cricothyroid
ligament and to the trachea below by the cricotracheal ligament. The cricothyroid
muscle attaches to the anterior and lateral borders of the cricoid cartilage, and the
inferior pharyngeal constrictor attaches to its posterior border. The posterior
superior aspect of the cricoid is notched, and on either side of the notch are
smooth surfaces for articulation with the bases of the 2 arytenoid cartilages. The
inner surface of the cricoid is lined with mucous membrane.
Arytenoid cartilages - paired, three-sided, pyramid-shaped bodies that lie on the
superior margin of the cricoid lamina. The anterior protrusion of the pyramid is
the vocal process which is connected to the vocal ligament. The muscular process
protrudes laterally, to which are attached the posterior and lateral cricoarytenoid
muscles. (Stretching between the posterior surfaces of the two arytenoids are the
transverse and oblique arytenoid muscles. Attached to the anterolateral surface of
the arytenoid are the thyroarytenoid muscle with its vocalis and thyroepiglottic
parts.)
Corniculate cartilages - paired, small cartilages that sit on top of the apices of the
arytenoids.
Cuneiform cartilages - paired, rod shaped bodies in the aryepiglottic fold lateral to
the epiglottis.
Epiglottic cartilage - an unpaired, spoon-shaped cartilage which is attached (by
the thyroepiglottic ligament) at its inferior tapered end (tubercle of the epiglottis)
to the superior thyroid notch. The superior end is free and curved anteriorly, while
the anterior surface is attached to the hyoid bone by the hyoepiglottic ligament. It
is covered by mucosa. The posterior surface of the epiglottis faces the vestibule of
the larynx. It is pitted to accommodate small mucous glands.
Membranes of the larynx:
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Thyrohyoid membrane - suspends the thyroid cartilage and thus the larynx from
the hyoid bone above. The median portion of this membrane is thickened, forming
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the median thyrohyoid ligament. Lateral thyrohyoid ligament on the sides of the
larynx extends between the superior horn of the thyroid cartilage and to the end of
the greater horn of the hyoid bone.
Quadrangular membrane - above the vocal ligament is a thin sheet of connective
tissue connecting the lateral part of the epiglottic cartilage with the arytenoid. Its
lower free margin, above the vocal ligament, is the vestibular ligament of the false
vocal (vestibular) folds.
Conus elasticus - is an elastic membrane hanging down like a sheet from the vocal
ligament above to the cricoid cartilage below. The lower attachment of this sheet
stretches in a semicircle from the base of one arytenoid to the other. The
thickened superior margins of the conus - the vocal ligaments - attach the vocal
processes of the arytenoids to the inner surface of the laryngeal prominence,
below the superior thyroid notch. This forms the V shape of the abducted vocal
ligaments when seen from above.
Hyoepiglottic and thyroepiglottic ligaments - attach the epiglottis to the hyoid
bone and thyroid cartilage anteriorly.
Cricotracheal ligament - connects the inferior border of the cricoid to the first ring
of the trachea.
8. Describe the actions of the intrinsic muscles of the larynx in tensing, relaxing,
abducting or adducting the vocal folds. (N 78C, 78D, 79, TG 7-26, 7-27, 7-28)
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Cricothyroid muscles (paired) - On the external surface of the larynx. Arise from
the anterior arch of the cricoid cartilage and fibers travel backward and upward to
insert into the inferior border of the thyroid cartilage. Action: pulls the thyroid
cartilage down and toward the cricoid. Result: increases the distance between the
arytenoids and the thyroid cartilage, tensing the vocal folds. Helps control pitch.
Posterior cricoarytenoid muscles (paired) - Lie on the dorsal surface of the cricoid
cartilage. Fibers originate near the posterior midpoint, and run laterally from there
in both directions to attach to the back of the muscular processes of the arytenoid
cartilages. Action: when muscles contract, they pull the muscular processes
posteriorly and the vocal processes laterally. Result: Abduction of the vocal folds.
These are the only abductors of the vocal folds. Without them, the vocal folds
adduct permanently, and you suffocate.
Lateral cricoarytenoid muscles (paired) - Originate from the upper anterior border
of the cricoid cartilage. Fibers pass posteriorly left and right and insert on the
anterior aspect of the muscular processes of the arytenoid cartilages. Action:
Upon contraction, muscular processes are pulled anteriorly and vocal processes
are pulled medially. Result: Adduction of the vocal folds.
Arytenoid muscles (two, but unpaired) - These muscles, oblique and transverse,
attach the posterior surfaces of the arytenoids to one another. Oblique fibers are
continuous with the aryepiglottic muscles, which help to pull epiglottis down
toward the larynx during swallowing. Action: Upon contraction, pulls the
arytenoids medially (toward each other). Result: Adduction of the vocal folds.
Thyroarytenoid muscles (paired) - Border the vocal ligaments. Arise from the
anterior inner surfaces of the thyroid laminae, deep to the laryngeal prominence,
and insert on the lateral borders of the arytenoid cartilages. Action: they pull the
arytenoid cartilages closer to the thyroid cartilages, Result: reduced tension of the
vocal ligament. In the process of shortening, these muscles also thicken and this
helps seal the glottis. Thus they are considered sphincters of the glottis.

Vocalis muscles (paired) - are composed of the fibers of thyroarytenoid muscles
closest to the vocal ligaments. Each vocalis attaches to the elastic tissue of the
vocal ligament. Action: Contraction affects frequency of vibration of the vocal
ligaments. Result: Control of pitch and the fine adjustments required in
vocalization.
9. Describe the innervation and vascular supply of the larynx. (N 76, 80, TG 7-26B, 726C, 7-28)
Innervation:

Vagus, through superior laryngeal and inferior laryngeal nerves, innervates the
entire larynx.
o Superior laryngeal, internal branch: the principal sensory nerve of the
larynx, sending fibers from the supraglottic portion of the larynx; also
sends parasympathetic fibers to the mucous glands of the interior of the
supraglottic portion of the larynx.
o Superior laryngeal, external branch: only innervates the cricothyroid
muscle.
o Inferior laryngeal: Is the continuation of the left and right recurrent
laryngeal nerves. It innervates all intrinsic muscles of the larynx except
cricothyroid.
Vascular supply:


Superior laryngeal artery, branch of the superior thyroid artery, pierces the
thyrohyoid membrane along with the internal branch of the superior laryngeal
nerve.
Inferior laryngeal artery, branch of the inferior thyroid artery, passes under the
inferior pharyngeal constrictor muscle along with the inferior laryngeal nerve.
Questions and Answers:
10. Identify the ascending pharyngeal artery (a branch of the external carotid) distributing
to the dorsal wall of the pharynx. Do you find any lymph nodes (retropharyngeal)?
Retropharyngeal lymph nodes are usually present in the tissue between visceral and
musculoskeletal parts of the neck, known as the retropharyngeal space, but difficult to
find unless they are enlarged by disease. They are associated with the deep cervical nodes
found in the carotid sheath just lateral to the space. (N 73, 136, TG 7-74)
11. Observe the pharyngobasilar fascia forming the pharyngeal wall above the superior
pharyngeal constrictor. What tissue is it?
The wall of digestive and respiratory tracts, of which the pharynx is common to both,
consists of a mucosal lining, a connective tissue layer - the submucosa - and a muscular
wall. The pharyngobasilar fascia is the submucosa of the pharyngeal wall. (N 67, TG 721)
12. Clear the stylopharyngeus muscle and trace to the pharynx. Between what two
muscles does it pass?
The stylopharyngeus muscle passes between the superior and middle pharyngeal
constrictors. (N 67, TG 7-21)
13. Consider the complete blood supply to pharyngeal constrictors. Innervation?
The pharynx is supplied by the ascending pharyngeal artery, branches of the facial,
maxillary and inferior thyroid. The pharynx receives nerves from the pharyngeal plexus
which is composed of branches of the glossopharyngeal nerve (sensory), the vagus
(motor and parasympathetic motor to the glands of the mucosa) and the sympathetic
trunk (vasomotor to the blood vessels of the pharynx). (N 69, 75, 125, 126, 130, 131, 136,
TG 7-22, 7-21, 7-20, 7-23, 7-24)
14. Define nasal, oral and laryngeal portions of pharynx. What boundaries separate these
regions?
The nasopharynx extends from the choanae anteriorly to the soft palate inferiorly; it is the
respiratory portion of the pharynx. The oropharynx extends from the soft palate above to
the epiglottis below and opens into the mouth anteriorly. The laryngopharynx extends
from the epiglottis to the beginning of the esophagus below. It opens into the larynx
anteriorly.
14a. What structures lie immediately deep (lateral) to the palatine tonsil? Where is the
lingual tonsil?
The superior pharyngeal constrictor muscle lies lateral to the palatine tonsil, along with
the vessels supplying the tonsil. The lingual tonsil is in the submucosa on the superior
surface of the root of the tongue just behind the sulcus terminalis. It is a large collection
of lymphoid nodules that give the posterior one-third of the tongue its warty appearance.
15. The cartilages of the larynx along with their articulations and membranes constitute a
separate, almost independent, musculoskeletal entity. What structural features differ in
male and female?
The thyroid cartilage in male and female are different in shape. In the female, the two
thyroid laminae meet in an angle of about 120 degrees. In the male, the thyroid laminae
meet at an angle of 90 degrees. Thus the laryngeal prominence (the so called "Adam's
apple") in the male is more obvious. The shape as well determines the length of the vocal
cords and their consequent pitch; the cords being shorter in women and thus a higher
pitched voice.
16. What is the action of the cricothyroid joint?
The cricothyroid muscle brings the arch of the cricoid and the thyroid cartilage together
with the pivot at this joint. During this action the vocal folds become more tense and the
pitch of the voice increases. Conversely paralysis of this muscle produces hoarseness of
voice.
17. What is the glottis?
The glottis is defined as the space between the true vocal folds. It is also called the rima
glottidis to differentiate it from the rima vestibuli, the space between the vestibular or
false vocal folds.
18. What is the source of the inferior laryngeal nerve and the inferior laryngeal artery?
The inferior laryngeal nerve is the terminal end of the recurrent laryngeal nerve. It is
motor to the intrinsic muscles of the larynx, while the recurrent laryngeal supplies the
trachea and esophagus as well. The inferior laryngeal artery is a branch of the inferior
thyroid artery; it accompanies the nerve into the space deep to the piriform recess.
19. Identify two structures that perforate the thyrohyoid membrane: the internal branch of
the superior laryngeal nerve and the superior laryngeal artery. What is the source of each?
The internal branch of the superior laryngeal nerve is a sensory nerve to the interior of the
larynx which arises from the vagus. The superior laryngeal artery and vein arise as the
first branches of the superior thyroid vessels. (N 69, 74, 126, TG 7-26, 7-28)
20. Does the external branch of the superior laryngeal nerve pass through or give off a
branch to the inferior pharyngeal constrictor muscle?
The external branch of the superior laryngeal nerve usually passes through the lower
portion of the inferior constrictor muscle (this portion a.k.a. cricopharyngeus m.)
supplying it and the cricothryroid muscle. (N 74, 75, 76, TG 7-20, 7-26)
Dissector Answers - Scalp, Cranial Cavity, Meninges & Brain
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Define the scalp, its structural layers, muscles, nerves, and vessels.
2. Identify the prominent landmarks on the internal surface of the skull base.
3. Identify the major blood vessels of the brain, the specializations of cranial
meninges, and cranial dural modifications.
4. Identify the cranial nerves on the brain and their courses through the skull base.
5. Identify the parts of the ventricular system and trace the flow of cerebrospinal
fluid from production to reabsorption.
Learning Objectives and Explanations:
1. Define the scalp, its layers, muscles, nerves, and vessels. (N98, N99A, N99B, N101,
N102, TG7-30)
The scalp consists of five layers of tissue. The first three (scalp proper) are connected
intimately and move as a unit in wrinkling the scalp.





Skin - thin except in the occipital region where it is thick. It has an abundant
arterial supply, good lymphatic and venous drainage, as well as numerous sweat
and sebaceous glands.
Connective tissue - thick, richly vascularized subcutaneous layer that is well
supplied with cutaneous (sensory) nerves. This second layer contains the arteries,
veins, and cutaneous nerves, which are held tightly in place by collagenous
bundles.
Aponeurosis (galea aponeurotica) - a strong tendinous sheath that covers the
calvaria as well as the frontalis and occipitalis portions of the epicranius muscle.
Laterally, the anterior and superior auricular muscles (moving the ear) also attach
to this aponeurosis.
Loose connective tissue - layer over the calvaria that allows for movement of the
first three layers of the scalp.
Pericranium (also called Periosteum) - the external bone of the calvaria. (WB
254).
For a detailed view of the distribution of the nerves and vessels of the scalp please see
255 WB.
2. Identify the prominent landmarks on the internal surface of the skull base. (N6, N7A,
N7B, N9, N11, TG7-07, TG7-08)
The internal surface of the skull is divided into three fossae (depressions):



Anterior cranial fossa - This fossa is shallow and the crista galli projects upward
from its surface. The cribriform plate contains multiple foramen through which
branches of the olfactory nerve pass. The lesser wing of the sphenoid marks the
posterior border of the anterior cranial fossa.
Middle cranial fossa - This fossa is of intermediate depth and is notable for
containing the sella turcica, which holds the pituitary. The bulk of the middle
cranial fossa is composed of the greater wings of the sphenoid and the squamous
portion of the temporal bones, upon which rest the temporal lobes. The posterior
border of the middle cranial fossa is a ridge of bone called the petrous portion of
the temporal bone. The middle cranial fossa contains the optic canal, superior
orbital fissure, foramen rotundum, foramen ovale, foramen spinosum, and
foramen lacerum.
Posterior cranial fossa - This fossa is relatively deep and contains the cerebellum.
Projecting posterior to the foramen magnum is the internal occipital protuberance.
The internal acoustic meatus is located on the petrous portion of the temporal
bone. The jugular foramen is anterolateral to the hypoglossal canal.
3. Identify the major blood vessels of the brain, the specializations of cranial meninges,
and cranial dural modifications. (N98A, N99B, N101, N102, N103, N104A, N104B,
N137, N138, N139, TG7-46, TG7-48, TG7-49, TG7-56A, TG7-56B, TG7-72, TG7-73)
Arterial supply




Internal carotid artery - gives rise to ophthalmic (which you will be responsible
for in a later lab), posterior communicating, anterior cerebral, and middle cerebral
arteries.
Vertebral arteries
1. Anterior spinal arteries - paired branches that unite in the midline.
2. Posterior inferior cerebellar arteries, from which arise the two posterior
spinal arteries
Basilar artery - formed by union of the vertebral arteries, it gives rise to anterior
inferior cerebellar, superior cerebellar arteries, and bifurcates into the posterior
cerebral arteries.
Circle of Willis or Cerebral arterial circle - forms an important means of collateral
circulation in case of obstruction. The circle itself has good collateral circulation,
but branches of the circle are end arteries and there is little collateral circulation in
the brain itself. Formed by the union of the anterior cerebral, anterior
communicating, posterior communicating, and posterior cerebral arteries.
Venous Return
Here is a diagram of the direction of venous return in the brain.
Meninges of the brain
I.
II.
Pia mater ("delicate mother")
o
is a delicate investment that is closely applied to the brain and dips into
fissures and sulci.
o
enmeshes blood vessels on the surface of the brain.
Arachnoid mater ("spidery mother")
o
is a filmy, transparent, spidery layer that is connected to the pia mater by
trabeculation.
o
is separated from the pia mater by the subarachnoid space, which is filled
with cerebrospinal fluid (CSF). It may contain blood after hemorrhage of a
cerebral artery (site of formation of subarachnoid hematoma).
o
projects into the superior sagittal sinus to form arachnoid villi, which serve
as sites where CSF diffuses into the blood.

Cerebrospinal fluid

is formed by vascular choroid plexuses in the ventricles of
the brain and is contained in the subarachnoid space.

circulates through the ventricles, enters the subarachnoid
space, and eventually is returned to the venous system
through the arachnoid granulations.

Arachnoid granulations

III.
are tuft-like collections of highly folded arachnoid that
project into the superior sagittal sinus and its lateral lacunae
(lateral extensions of the superior sagittal sinus).

release CSF into the superior sagittal sinus and often
produce erosion or pitting of the inner surface of the
calvaria (granular foveolae).
Dura mater ("tough mother")
o
outermost covering
o
two layers
1. periosteal dura - lines the cranial bones
2. meningeal layer - inner layer that is sometimes separated from the
periosteal layer, forming dural venous sinuses and partitions
Projections of the dura mater
 Falx cerebri is the sickle-shaped double layer of the dura mater,
lying between the cerebral hemispheres. It is attached anteriorly to
the crista galli and posteriorly to the tentorium cerebelli. Its
inferior concave border is free and contains the inferior sagittal
sinus, and its attachment to the frontal and parietal bones at the
sagittal suture encloses the superior sagittal sinus.
 Falx cerebelli is a small sickle-shaped projection between the
cerebellar hemispheres. It is attached to the posterior and inferior
parts of the tentorium and contains the occipital sinus in its
attachment to the occipital bone.
 Tentorium cerebelli is a crescentic fold of dura mater that supports
the occipital lobes of the cerebral hemispheres and covers the
cerebellum. Its internal concave border is free and defines the
tentorial notch, whereas its attachment to the occipital and
temporal bones encloses the transverse sinus posteriorly and the
superior petrosal sinus anteriorly.
 Diaphragma sellae is a circular, horizontal fold of dura that forms
the roof of the sella turcica, covering the pituitary gland. It has a
central aperture for the hypophyseal stalk or infundibulum.
4. Identify the cranial nerves on the brain and their courses through the skull base. (N11,
N104, N114, TG7-07, TG7-51, TG7-52)
Nerve
Cranial Exit
I
Olfactory
Cribriform plate
II
Optic
Optic canal
III
Oculomotor
Superior orbital fissure
IV
Trochlear
Superior orbital fissure
V
Trigeminal
Superior orbital fissure (V1); f. rotundum (V2); f. ovale (V3)
VI
Abducens
Superior orbital fissure
VII Facial
Enters internal auditory meatus, travels through petrous
temporal bone, leaves via stylomastoid f.
VIII Vestibulocochlear Enters internal auditory meatus, remains within petrous
temporal bone
IX
Glossopharyngeal Jugular f.
X
Vagus
Jugular f.
XI
Accessory
Jugular f.
XII Hypoglossal
Hypoglossal canal
5. Identify the parts of the ventricular system and trace the flow of cerebrospinal fluid
from production to reabsorption. (N108, TG7-46, TG7-49, TG7-50A, TG7-50B)
A. Parts of the ventricular system
o The cerebral hemispheres are hollow, each containing a lateral ventricle.
The ventricles contain a tuft of blood vessels called the choroid plexus,
which secretes CSF. The lateral ventricles communicate with the midline
third ventricle by way of the interventricular foramina. A thin membrane
and attached choroid plexus roofs the third ventricle. In the midbrain, the
narrow cerebral aqueduct connects the third and fourth ventricles.
o The fourth ventricle lies between the pons, cerebellum, and the medulla. It
communicates with the cerebral aqueduct, the central canal of the spinal
cord, and the subarachnoid space. The roof of the fourth ventricle caudal
to the cerebellum, the tela choroidea, is thin like that of the third ventricle
and has a choroid plexus. It is perforated by a small median aperture and
two lateral apertures that allow cerebrospinal fluid to exit the ventricular
system and bathe the brain and spinal cord. (WB 29)
B. The flow of CSF from production to reabsorption
o CSF is secreted (produced) by the choroidal epithelial cells of the choroid
plexuses in the lateral, third, and fourth ventricles.
o CSF leaves the lateral ventricles through the interventricular foramina and
enters the third ventricle. From there CSF passes through the cerebral
aqueduct into the fourth ventricle. It leaves this ventricle through its
median and lateral apertures and enters the subarachnoid space, which is
continuous around the spinal cord and brain. The arachnoid forms various
spaces around the brain called cisterns, filled with CSF, such as the
interpeduncular and quadrigeminal cisterns. CSF passes into the
extensions of the subarachnoid space around the optic nerves.
C. Reabsorption of CSF (reabsorption into the venous system) - the main site of CSF
absorption (reabsorption) into the venous system is through arachnoid
granulations. The subarachnoid space containing CSF extends into the arachnoid
granulations, which in turn project upward through the dura into the superior
sagittal sinus and lateral projections from it called lateral lacunae.
Summary: CSF is formed in the brain in the choroid plexus of ventricles, and drains via
arachnoid granulations projecting into the superior sagittal sinus.
Questions and Answers:
1. Note the choroid plexus; where is it found and what is its function? (TG7-50A, TG750B)
Choroid plexuses are relatively large, tuft-like carpets of capillaries. They lie in the floors
of the lateral ventricles and the roofs of the third and fourth ventricles. They give off
cerebrospinal fluid, filling the ventricles.
2. The spread of infection is mainly facilitated through what layer of the scalp? (N98A,
N101, N102, TG7-46, TG7-49)
The subaponeurotic connective tissue layer (areolar tissue) of the scalp facilitates the
spread of infection because of its loose character.
3. Note dural attachment to the calvaria and the base of the skull. Is there any difference?
(N98A, N101, N102, TG7-46, TG7-47, TG7-48, TG7-49)
The spinal dura consists of one layer and is a tube with lateral extensions covering nerve
rootlets. The cranial dura, on the other hand, splits to form two layers.
1. An external periosteal layer is the periosteum covering the internal surface of the
calvaria.
2. An internal meningeal layer, a strong fibrous membrane that is continuous at the
foramen magnum with the spinal dura mater covering the spinal cord.
The periosteal layer adheres to the internal surface of the skull, and its attachment is
tenacious along the suture lines and in the cranial base. The external periosteal layer is
continuous at the cranial foramina with the periosteum on the external surface of the
calvaria; it is NOT continuous with the dura mater of the spinal cord. In most areas, the
meningeal layer is intimately fused with the periosteal layer and cannot be separated from
it. The fused external and internal layers of dura over the calvaria can be easily stripped
from the cranial bones. A blow to the head can detach the periosteal layer from the
calvaria without fracturing the cranial bones. In the cranial base the two dural layers are
firmly attached and difficult to separate from the bones. Consequently, a fracture of the
cranial base tears the dura and results in leakage of CSF.
4. Examine falx cerebri, falx cerebelli, tentorium cerebelli, and diaphragma sellae. Are
these infoldings periosteal or meningeal? Define attachments and relationship of each and
the compartmentalization of the cranial cavity produced by these infoldings. (N103,
N104A, N104B, TG7-47, TG7-48, TG7-49A, TG7-49B)
The internal meningeal layer of dura draws away from the external periosteal layer of
dura to form dural infoldings, which separate the regions of the brain from each other and
form dural venous sinuses. These separations in the dural layers form the dural venous
sinuses (compartments). See the objective question above for attachments and
relationships of these dural infoldings.
5. What does each compartment contain? (N103, N104A, N104B, TG7-47, TG7-49)
The falx cerebri helps form the superior and inferior sagittal sinuses. The tentorium
cerebelli separates the cerebellum from the cerebral hemispheres. In the line of the
junction between the falx cerebri and the tentorium cerebelli lies the straight sinus. The
diaphragma sellae is a horizontal duplication of the meningeal dura that roofs the sella
turcica. The falx cerebelli is a partitioning of the dura which separates the cerebellar
hemispheres. It contains the occipital sinus. (WB 323-4)
6. What is the tentorial notch? (N104A, N104B, TG7-47)
The tentorial notch is the opening in the tentorium cerebelli for the brainstem
(specifically the midbrain).
7. Observe meningeal arteries in all cranial fossae. Which is the largest? How is it held
within the dura? Relation to greater wing of sphenoid? (Significance?) (N99B, N104A,
N104B, TG7-51)
The largest of the meningeal arteries is the middle meningeal artery. It is a branch of the
maxillary artery. It goes through the foramen spinosum and supplies most of the dura
mater except for the floors of the anterior and posterior cranial fossae. It runs forward for
a short distance in a groove on the greater wing of the sphenoid bone, lying between bone
and dura, and then divides into anterior and posterior branches. (WB 326, 269)
Significance: The dura is sensitive to pain, especially where it is related to the dural
venous sinuses and meningeal arteries. Consequently, piercing the dura where the
meningeal arteries enter the base of the skull or near the vertex causes pain and is a major
source of headaches. In addition, the rupture of the middle meningeal artery by fracture
of the greater wing of the sphenoid bone causes an epidural hematoma.
8. What is the innervation of dura? (N104A, N104B, TG7-51)
The dura is innervated by all three divisions of the trigeminal nerves, the vagus nerves,
and the hypoglossal nerves.
A. Anterior and posterior ethmoidal branches of the ophthalmic division of the trigeminal
nerve in the anterior cranial fossa.
B. Meningeal branches of the maxillary and mandibular divisions of the trigeminal nerve
in the middle cranial fossa.
C. Meningeal branches of the vagus and hypoglossal nerves in the posterior cranial fossa.
9. What cranial nerves exit through the jugular foramen? (N11, N104A, N104B, TG7-07,
TG7-51)
Cranial nerves IX, X, and XI.
10. Sinus rectus (is a portion of the great cerebral vein attached to it?) (N103, N104A,
N104B, TG7-47, TG7-49)
The sinus rectus, a.k.a. the straight sinus, is formed by the union of the inferior sagittal
sinus with the great cerebral vein.
11. Confluens of sinuses (significance, location, pattern, and variations). (N103, N104A,
N104B, TG7-47, TG7-49)
The confluens of sinuses is a meeting place of the superior sagittal, straight, occipital, and
the right and left transverse sinuses. This junction is a dilitation at one side of the internal
occipital protuberance. Sometimes it is a region of actual confluence, and sometimes the
superior sagittal and straight sinuses (either or both) bifurcate here to form the right and
the left transverse sinuses. (WB 325).
12. Superior petrosal sinus (connects what?) (N103, N104A, N104B, TG7-47)
The superior petrosal sinus connects the posterior end of the cavernous sinus to the bend
marking the transition between the transverse and sigmoid sinuses. It receives cerebellar
and inferior cerebral veins and veins from the tympanic cavity. (WB 326) .
13. Define emissary veins and the mastoid, condyloid, parietal, and ophthalmic emissary
veins. (N98A, N101, N102, TG7-73)
The emissary veins are small veins connecting the dural venous sinuses with the veins of
the scalp. They are valveless and, as a result, may conduct blood inward or outward in
accordance with the pressure existing in the sinuses and in the external veins. Some are
constant; others occur occasionally. The superior ophthalmic vein is the largest vein of
this type. It connects the angular vein of the face with the cavernous sinus. The mastoid
emissary vein unites the posterior auricular vein with the sigmoid sinus. The parietal
emissary vein occupies the parietal foramen and connects the veins of the scalp with the
superior sagittal sinus. The emissary vein of the foramen cecum connects the veins of the
nasal cavity with the superior sagittal sinus. The condyloid canal, when present, transmits
an emissary vein which passes between the lower end of the sigmoid sinus and veins of
the suboccipital triangle of the neck. (WB 326)
14. Remove the blood from the cavernous sinus and note trabeculae. Do the two sides
communicate? (N104A, N104B, TG7-47, TG7-60)
The cavernous sinuses usually communicate (WB 325). They are found on each side of
the sella turcica and the body of the sphenoid bone and lie between the meningeal and
periosteal layers of the dura mater.
15. Expose the internal carotid artery (course?) (N104A, N104B, N138, N139, TG7-47,
TG7-60, TG7-72)
The internal carotid artery:




has no branches in the neck
ascends within the carotid sheath in company with the vagus nerve and the
internal jugular vein.
enters the cranium through the carotid canal in the petrous part of the temporal
bone.
in the middle cranial fossa, gives rise to the ophthalmic artery and the anterior and
middle cerebral arteries and the posterior communicating artery.
16. Look for arachnoid granulations (villi). What is their function? (N98A, N101, N102,
N108, TG7-46, TG7-49, TG7-50)
The arachnoid granulations are tuftlike collections of highly folded arachnoid that project
through the dura mater into lateral lacunae of the superior sagittal sinus and into other
dural sinuses. Through their thin membranes, the cerebrospinal fluid is passed into the
blood stream. (WB 323)
17. Examine the pia mater on the brain. How does it differ from the arachnoid mater in
covering the brain? (N98A, N101, N102, TG7-46, TG7-49)
The pia mater on the brain is a delicate, intimate, areolar investment of brain and spinal
cord that enmeshes the blood vessels on their surfaces. It is a vascular membrane. On the
other hand, the arachnoid is a delicate transparent membrane composed of a blend of
collagenous and elastic fibers and squamous mesenchymal epithelial cells. It is NOT
vascular and is NOT attached directly to the surface of the brain or spinal cord.
Arachnoid trabeculae are thin strands that conect the arachnoid to the pia mater. (WB
322-23)
18. What is the arterial circle of Willis? (N139, TG7-56A, TG7-56B)
The circle of Willis, a.k.a. cerebral arterial circle, is an important anastomosis at the base
of the brain between the following arteries:





Anterior cerebral arteries
Anterior communicating arteries
Internal carotid arteries
Posterior communicating arteries
Posterior cerebral arteries
The various components of the cerebral arterial circle give many small branches to the
brain.
Dissector Answers - Parotid Gland & Face
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Describe the location of the parotid salivary gland posterior and deep to the ramus
of the mandible, within the parotid fossa.
2. Identify three main neurovascular structures that traverse the gland: the facial
nerve, the retromandibular vein and external carotid artery.
3. Identify the branches of the facial nerve in the face.
4. Identify some exemplary muscles of facial expression acting on the oral opening.
5. Trace the course of the facial artery and facial vein in the face.
Learning Objectives and Explanations:
1. Describe the location of the parotid salivary gland posterior and deep to the ramus of
the mandible, within the parotid fossa (N4, N25, TG7-30A, TG7-30B, TG7-31A)
The parotid gland extends into the parotid fossa, anteroinferior to the external acoustic
meatus, wedged between the ramus of the mandible and the mastoid process. The apex of
the parotid gland is posterior to the angle of the mandible, and its base is related to the
zygomatic arch.
2. Identify three main neuromuscular structures that traverse the gland: the facial nerve,
the retromandibular vein and external carotid artery. (N25, N69, N70, TG7-19, TG7-31)
From superficial to deep, the structures traversing the gland are arranged: facial nerve and
its branches, retromandibular vein, and external carotid artery. Retromandibular vein is
formed by the union of the superficial temporal and maxillary veins. It divides into
anterior and posterior divisions and drains the sides of the head, scalp, and deep face.
3. Identify the branches of the facial nerve in the face. (N25, N123, TG7-87)
Branches of the facial nerve include: temporal, zygomatic, buccal, marginal mandibular
and cervical. The temporal branch of the facial nerve emerges from the superior border of
the parotid gland and crosses the zygomatic arch. The zygomatic branches pass via two
or three branches to the eye to innervate the inferior part of the orbicularis oculi and other
facial muscles inferior to the orbit. Buccal branches pass external to the buccinator to
innervate this muscle and muscles of the upper lip. The (marginal) mandibular branch
innervates the muscles of the lower lip and chin. It emerges from the inferior border of
the parotid gland and crosses the inferior border of the mandible deep to the platysma to
reach the face. The cervical branch passes from the inferior border of the parotid gland to
the mandible to innervate the platysma.
4. Identify some exemplary muscles of facial expression acting on the oral opening.
(N26, N54, N69, N123, TG7-29, TG7-30, TG7-31, TG7-87)
Zygomaticus major, levator labii superioris, depressor labii inferioris, levator anguli oris,
depressor anguli oris, and orbicularis oris, and buccinator are all innervated by the facial
nerve (CN VII) and supplied by the facial artery. Zygomaticus major arises from the
upper lateral surface of the zygomatic bone to insert into the skin of the upper lip. It
elevates and draws the corner of mouth laterally. Levator labii superioris originates from
the inferior margin of the orbit to insert on the skin of upper lip. It elevates the upper lip.
Levator anguli oris attaches superiorly to the infraorbital margin and inferiorly to the
angle of the mouth. Depressor anguli oris depresses the angle of the mouth. Posterior
fibers of the platysma assist with this movement. Depressor labii inferioris, lateral to the
mentalis, attaches inferiorly to the mandible and merges superiorly with its contralateral
partner and the orbicularis oris and draws the lip inferiorly and slightly laterally.
Orbicularis oris originates from the skin and fascia of the lips and inserts in the skin and
fascia of the lips. It purses the lips. The buccinator runs from the mandible to the angle of
the mouth and lateral portion of the lips. It pulls the corner of the mouth laterally. It is
important to note that although this muscle lies fairly deeply in the face, it is still
innervated by the facial nerve, not the trigeminal nerve (which penetrates buccinator with
branches of the buccal NERVE, a sensory nerve, as opposed to buccal BRANCHES of
facial nerve, that are motor).
5. Trace the course of the facial artery and facial vein in the face. (N16, N69, N70, TG719, TG7-31)
Facial artery: arising from the external carotid, it winds to the inferior border of the
mandible deep to the platysma. It crosses the mandible, buccinator, and maxilla as it
courses over the face to the medial angle of the eye. The facial artery lies deep to the
zygomaticus major and levator labii superioris muscles. It eventually anastomoses with
the ophthalmic artery.
Facial vein: begins near the medial angle of the eye and the inferior border of the orbit as
the continuation of the angular vein. The facial vein runs inferolaterally through the face,
posterior to the facial artery.
Dissector Answers - Infratemporal Fossa & Oral Cavity
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Identify the masticatory muscles and give their functions.
2. Define the boundaries and contents of the infratemporal fossa.
3. Identify the branches of the trigeminal nerve and their functions related to
mastication and sensation from the face.
4. Identify the chorda tympani nerve and give its function.
5. Describe the structure and function of the temporomandibular joint.
6. Identify the muscles bordering the submandibular and paralingual spaces.
7. List and identify the major nerves and vessels of these spaces.
8. Describe the submandibular and sublingual salivary glands and give their
innervations.
9. List the muscles of the tongue and describe their origins.
10. Describe the oral cavity, its oral vestibule and dental arches (including temporary
and permanent dentitions), and the hard and soft palate.
Learning Objectives and Explanations:
1. Identify the masticatory muscles and give their functions. (N54A, N54B, N55, N69,
N46, TG7-31, TG7-34, TG7-85)
Masseter muscle
Origin: Zygomatic arch
Insertion: Lower half of the mandibular ramus
Blood supply: Masseteric artery
Nerve supply: Masseteric nerve
Action: Mandibular elevation (powerful crusher of food)
Temporalis muscle
Origin: Temporal fossa, temporal fascia
Insertion: Coronoid process and temporal crest of the mandibular ramus
Blood supply: Anterior and posterior deep temporal arteries
Nerve supply: Anterior and posterior deep temporal nerves
Action: Elevation and retraction of the mandible
Medial pterygoid
Origin: Medial surface of lateral pterygoid plate
Insertion: Medial surface of the ramus of the mandible (below mandibular foramen)
Blood supply: Arterial twigs of the maxillary artery
Nerve supply: Nerve to medial pterygoid
Action: Protraction and elevation of the mandible
Lateral pterygoid
Origin: Upper head - base of the skull (greater wing of sphenoid); Lower head - lateral
surface of lateral pterygoid plate
Insertion: Upper head - capsule and articular disc of the TMJ; Lower head - pterygoid
fovea of the condylar neck
Blood supply: Twigs from the maxillary artery
Nerve supply: Short nerves from the mandibular division of the trigeminal nerve
Action: Protraction and opening movements of mandible
2. Define the boundaries and contents of the infratemporal fossa. (N4, N54A, N54B,
,N55, TG7-04A, TG7-32A, TG7-32B)
Boundaries:
Medial: Lateral pterygoid plate.
Lateral: Medial surface of the ramus of the mandible.
Anterior: Tuberosity of the maxilla.
Posterior: Deep part of the Parotid region.
Superior: Base of the skull (greater wing of sphenoid bone)
Inferior: Medial pterygoid muscle.
Contents:
Medial pterygoid muscle
Lateral pterygoid muscle
Maxillary artery and vein
Pterygoid plexus of veins
Mandibular division of trigeminal nerve
Otic ganglion
3. Identify the branches of the trigeminal nerve and their functions related to mastication
and sensation from the face. (N45, N46, N122, TG7-29, TG7-81C, TG7-81D, TG7-85)
V1: Ophthalmic division
General sensory from the cornea, skin of forehead, scalp, eyelids, nose, and mucosa of
nasal cavity and paranasal sinuses
V2: Maxillary division
General sensory from the skin of the face over the maxilla, including upper lip, maxillary
teeth, mucosa of nose, maxillary sinuses, and palate
V3: Mandibular division (major nerve supply to masticatory muscles)
Sensory branches:





Auriculotemporal nerve - passing across roof of parotid fossa and emerges
between temporomandibular joint and external acoustic meatus. Sensory nerve to
auricle, scalp over temporal region, and temporomandibular joint.
Inferior alveolar nerve - passes through mandibular foramen into mandibular
canal, sensory for mandible and all mandibular teeth. This is the nerve
anesthetized by dentists when working on the mandibular teeth.
Lingual nerve - general sensory to the anterior 2/3 of the tongue.
Receives the chorda tympani, a branch of the facial nerve, from behind, which
provides the lingual nerve with preganglionic parasympathetic fibers (for
submandibular and sublingual glands) AND special sensory fibers for taste (for
the anterior 2/3 of the tongue)
Buccal nerve - sensory from skin and mucosa of cheek area
Motor Nerves (to all masticatory muscles):




Anterior and posterior deep temporal nerves
Nerves to medial and lateral pterygoids
Masseteric nerve
Mylohyoid nerve - off the inferior alveolar nerve; innervates the mylohyoid
muscle and anterior belly of the digastric muscle.
4. Identify the chorda tympani nerve and give its function. (N46, N123, TG7-37, TG7-84,
TG7-88B)
Chorda tympani is a branch of the facial (CN VII) nerve that carries taste fibers from the
anterior two-thirds of the tongue and joins the lingual nerve in the infratemporal fossa. In
addition, the chorda tympani carries preganglionic parasympathetic fibers (secretomotor
fibers) for the submandibular and sublingual salivary glands.
5. Describe the structure and function of the temporomandibular joint. (N14, TG7-32B,
TG7-32C, TG7-33)
The TMJ is both a hinge and gliding synovial joint, with an articular disc present between
the mandibular condyle and both the mandibular fossa and articular eminence on the
temporal bone. With the fibrous capsule attaching to the perimeter of the articular
surfaces and the edges of the articular disc, two articular cavities are formed. The upper
one is between the articular disc and temporal bone, while the lower one is between the
disc and mandibular condyle. The lateral and medial TM ligaments limit the posterior
movements of the mandible. Movements involved include: hinge movement at the lower
joint and gliding at the upper joint. The joint is innervated by the auriculotemporal nerve.
6. Identify the muscles bordering the submandibular and paralingual spaces. (N27, N28,
N46, N53A, N53C, N59, N63, TG7-12, TG7-37A, TG7-37B, TG7-38)
MUSCLE ORIGIN INSERTION ACTION INNERVATION
NOTES
mylohyoid nerve
elevates
[from inferior
body of hyoid and draws
Digastric
alveolar nerve, a
forms anterior
digastric via a fibrous
forward
muscle,
branch of the
boundary of
fossa of
loop over an
hyoid
anterior
mandibular
submandibular
mandible intermediate bone;
belly
division of the
triangle
tendon
depresses
trigeminal nerve
mandible
(CN V3)]
Digastric
muscle,
posterior
belly
mastoid
notch of
temporal
bone
elevates
body of hyoid and
via a fibrous
retracts
facial nerve (CN
loop over an
the hyoid
VII)
intermediate bone;
tendon
depresses
mandible
splits around
intermediate
posterior
tendon of
side of the
Stylohyoid
digastric to
styloid
insert on the
process
body of the
hyoid bone
elevates
and
facial nerve (CN
retracts
VII)
the hyoid
bone
elevates
the hyoid
mylohyoid midline raphe bone and
Mylohyoid line of
and body of
tongue;
mandible the hyoid bone depresses
the
mandible
mental
Geniohyoid spines of
mandible
mylohyoid nerve
[from inferior
alveolar nerve, a
branch of the
mandibular
division of the
trigeminal nerve
(CN V3)]
C1 ventral ramus
elevates
via fibers carried
body of hyoid hyoid;
by hypoglossal
bone
depresses
nerve (i.e., ansa
mandible
cervicalis fibers)
forms posterior
boundary of
submandibular
triangle
medial and
parallel to
posterior belly
of digastric in
submandibular
triangle
paired
mylohyoid
muscles form
the muscular
floor of oral
cavity
adjacent to the
midline and
superior to
mylohyoid


These muscles are all considered suprahyoid muscles. All "serve in the
swallowing reflex to elevate the tongue and floor of the mouth. They also help
open the jaw when the hyoid bone is held down by the infrahyoid muscles."
(W&B 214)
Note: W&B (277) points out that "the paralingual space...is continuous with the
space of the submandibular triangle." Although the hyoglossus, a tongue muscle,
is found in the submandibular triangle, it will be fully treated with the other
tongue muscles in Objective 9.
7. List and identify the major nerves and vessels of these spaces. (N46, N59, N122,
N123, N126, N69, N70, TG7-18, TG7-19, TG7-40B, TG7-40C, TG7-81, TG7-84, TG794)
SENSOR
NERVE
SOURCE
BRANCHES MOTOR
NOTES
Y
inferior
alveolar (from
to mylohyoid mandibular
none
division of
trigeminal, V3)
lingual n.
mandibular
division of
none
trigeminal, V3
preganglionic
submandibul parasympatheti
ar ganglion c from chorda
tympani n.
chorda
tympani
facial (CN
VII)
hypoglossal
n. (CN XII)
hypoglossal
nucleus of
medulla in
brain
to mylohyoid
m.,
terminates in
none
anterior belly
of digastric
m.
none
arises near
lingula of
mandible (and
often grooves
the medial
surface of the
ramus)
forms
hammock for
general
submandibular
sensation
duct by
to anterior
crossing it
two-thirds
twice in
of tongue
paralingual
space
postganglionic
parasympatheti
c to
submandibular
and sublingual
glands
secretomotor
to
submandibul
none
ar and
sublingual
glands
hangs off
lingual nerve
just above deep
part
submandibular
gland in the
paralingual
space
none
secretomotor
to
submandibul
ar and
sublingual
glands
indistinguishab
le from lingual
nerve in
submandibular
and paralingual
spaces
none
intrinsic and
extrinsic
none
muscles of
tongue
taste to
anterior
two-thirds
of tongue
only motor
nerve to tongue
ARTERY SOURCE
facial
external
carotid a.
submental facial a.
lingual
deep
lingual
external
carotid a.
lingual a.
sublingual lingual a.
VEIN
facial vein
submental
vein
BRANCHES
ascending palatine a.,
tonsilar br., submental
a., superior and
inferior labial as., lat.
nasal br., angular a.
SUPPLY
lower part of
palatine tonsil,
submandibular
gland, facial
muscles, & fascia
none
sublingual gland,
submental triangle
deep to
submandibular
gland
none
suprahyoid br., dorsal
tongue, suprahyoid
lingual brs., deep
muscles, palatine
lingual a., sublingual
tonsil
a.
runs deep to
hyoglossus m.
none
anterior tongue
terminal branch of
lingual a. from
bifurcation deep to
hyoglossus m.
none
sublingual gland,
mylohyoid m.
mucous membranes
of floor of mouth
terminal branch of
lingual a. from
bifurcation deep to
hyoglossus m.
TRIBUTARIES
submental vein,
others
none
NOTES
DRAINS INTO
REGION
DRAINED
common trunk for
lingual, facial,
submandibular
retromandibular
gland and others
vs., then internal
jugular
facial v.
NOTES
superficial to
submandibular
gland
submandibular
triangle anterior
to submandibular
gland, including
sublingual gland
vena
accompanies CN
comitans of
XII, usually
deep lingual v.,
tongue,
the
lingual v.
inferior to n.,
sublingual v.
sublingual region
hypoglossal
runs on
n.
hyoglossus m.
8. Describe the submandibular and sublingual salivary glands and give their innervations.
(N46, N61, N123, N133, TG7-31, TG7-37, TG7-40, TG7-84)
Submandibular gland: This salivary gland occupies most of the posterior part of the
submandibular triangle. The superficial portion is larger and lies inferior to the
mylohyoid muscle directly underneath the superficial layer of cervical fascia. The deep
portion folds around the posterior edge of the mylohyoid muscle to lie deep in the
sublingual space between the mylohyoid and hyoglossus muscles. The 5 cm long
submandibular duct arises from the deep part of this gland and passes forward and
medialward to open in the sublingual caruncle at the side of the lingual frenulum. The
facial artery and vein supply this gland, and lymphatic drainage is to the submandibular
lymph nodes.
Innervation of submandibular gland:


Sympathetic nerves from the superior cervical sympathetic ganglion reach the
submandibular gland via the facial plexus along the facial artery.
Parasympathetic innervation comes from the chorda tympani branch of the facial
nerve (CN VII). The chorda tympani gives rise to the submandibular ganglion,
and the gland is innervated by postganglionic parasympathetic fibers from this
ganglion.
Sublingual gland: This is the smallest salivary gland. It is located beneath the oral
mucosa in the floor of the mouth between the mandible on one side and the genioglossus
and hyoglossus muscles on the other side. The sublingual gland sits on the mylohyoid
muscle. Unlike the submandibular gland, which drains via one large duct, the sublingual
gland drains via approximately 12 small ducts along the sublingual fold along the floor of
the mouth. (This occurs basically in a line behind the sublingual caruncle.) Blood supply
is from the sublingual branch of the lingual artery and from the submental branch of the
facial artery.
Innervation of the sublingual gland: Same as the submandibular gland.


Sympathetic innervation comes from the superior cervical sympathetic ganglion
via a plexus along the facial artery.
Parasympathetic innervation comes from postganglionic fibers from the
submandibular ganglion. The submandibular ganglion receives preganglionic
fibers from the chorda tympani branch of the facial nerve (CN VII).
9. List the muscles of the tongue and describe their origins. (N53A, N53C, N59, N63,
N68, N126, TG7-40, TG7-38)
MUSCLE ORIGIN INSERTION ACTION INNERVATION
NOTES
Hyoglossus
body and
greater
intrinsic
horn of the muscles of
hyoid
the tongue
bone
depresses
side of
tongue;
retracts
tongue
inferior
fibers
mental
protrude
spine on fans out to
tongue;
inner
insert into the
Genioglossus
middle
aspect of tongue from
fibers
mental
tip to base
depress
symphysis
tongue;
superior
this extrinsic
muscle of the
hypoglossal nerve
tongue lies in
(CN XII)
submandibular
triangle
this extrinsic
muscle of the
tongue is fan
hypoglossal nerve
shaped and lies
(CN XII)
vertically next
to the median
plane
fibers draw
tip back and
down
Styloglossus
styloid
process
Superior
base of
longitudinal tongue
Inferior
base of
longitudinal tongue
Transverse
lingual
side of the
tongue
this extrinsic
retracts and
muscle runs
hypoglossal nerve
elevates
longitudinally
(CN XII)
tongue
along the side
of the tongue
apex of
tongue
intrinsic
muscle
hypoglossal nerve immediately
(CN XII)
under mucous
membrane of
dorsum
apex of
tongue
intrinsic
muscle runs
between
hypoglossal nerve genioglossus
(CN XII)
and hyoglossus
on inferior
surface of
tongue
submucous
septum of
tissue at side
tongue
of tongue
compresses
sides of
tongue;
hypoglossal nerve
shapes
(CN XII)
tongue for
speech and
mastication
intrinsic
muscle runs
transversely
between
superior and
inferior
longitudinal
layers
shapes
intrinsic
tongue for hypoglossal nerve muscle with
Vertical
speech and (CN XII)
fibers at border
mastication
of tongue
10. Describe the oral cavity, its oral vestibule and dental arches (including temporary and
permanent dentitions), and the hard and soft palate. (N56, N57A, N57B, N63, TG7-38,
TG7-32)
The oral cavity extends from the lips to the palatopharyngeal folds. The oral vestibule lies
between the lips and the teeth.
superior inferior
surface of surface of
tongue
tongue
The dental arches, upper and lower, are made, on each side, of 2 incisors, 1 canine, 2
premolars, and 3 molar teeth for the permanent dentition, and 2 incisors, 1 canine, and 2
molars for the temporary or deciduous dentition.
The hard palate is formed primarily by the palatine processes of the maxillary bones, with
the horizontal processes of the palatine bones forming the posterior third. The soft palate
stretches posteriorly. It is a fibromuscular septum that can be moved to close off the
nasopharynx.
Questions and Answers:
12. Can you find the deep temporal nerves and arteries? (N46, N69, TG7-34, TG7-85)
They should be present innervating and feeding the temporalis muscle, respectively. The
anterior and posterior deep temporal arteries are branches of the maxillary artery, and
their accompanying nerves are branches of mandibular division of trigeminal.
13. What is the articular eminence? (N14, TG7-06)
The articular eminence is a projection of bone at the anterior margin of the mandibular
fossa.
14. Consider the condylar movements at each (joint cavity formed by the articular
capsule). (N14, TG7-33)
See above, but briefly:
Hinge movement at the lower joint (initiation of mandibular opening)
Gliding at the upper joint (termination of mandibular opening).
15. What kind(s) of fibers does it (chorda tympani) carry? (N46, N123, TG7-84)
See above, objective 4.
16. Identify other branches of the mandibular division of the trigeminal, a mixed motor
and sensory nerve. (N46, TG7-84A, TG7-84B, TG7-84C, TG7-84D, TG7-85A, TG785B)
See above, objective 3.
17. Accompanying autonomic fibers? Otic ganglion? (N46, N125, TG7-84)
The autonomic fibers from the chorda tympani were mentioned above (objective 4).
Other fibers present involve the otic ganglion. Specifically, this structure is a
parasympathetic ganglion just below the foramen ovale, which receives preganglionic
parasympathetic fibers from the glossopharyngeal nerve (CN IX) via the lesser petrosal
nerve. Postganglionic parasympathetic fibers emerging from the ganglion join the
auriculotemporal nerve and reach the parotid gland.
18. Define the boundaries of the submandibular triangle. (N28, TG7-02, TG7-12)
The submandibular triangle is defined by the inferior border of mandible and the anterior
and posterior bellies of digastric muscle. Please note that the submandibular triangle is
the "suprahyoid portion of the anterior cervical triangle" (W&B 213)
19. Trace the facial artery and vein noting relations with the submandibular gland (which
one is superficial or deep to the gland?). (N69, N70, TG7-19)
The facial artery is deep to the superficial portion of the submandibular gland. The facial
vein crosses the superficial surface of the submandibular gland
20. Can you find the mylohyoid nerve? (N46, TG7-85)
The mylohyoid nerve arises from the inferior alveolar nerve, which is in turn a branch of
the mandibular division of the trigeminal nerve (CN V3). It arises near the lingula of the
mandible. The inferior alveolar nerve continues its course through the mandibular
foramen, but the mylohyoid nerve stays on the medial surface of the mandible. This
makes the nerve readily identifiable, as it is plastered to the inside of the mandible.
21. Locate the mylohyoid nerve (what muscles does it supply; what does it arise from?)
(N46, TG7-85)
The mylohyoid nerve supplies the mylohyoid muscle before burying itself in the anterior
belly of the digastric muscle.
22. On the tongue, identify the foramen cecum (significance?). (N58, TG7-39)
The foramen cecum is a small pit on the dorsum of the tongue located in the midline. It is
at the apex of the sulcus terminalis. It is an embryological remnant marking the site of the
diverticulum of the thyroid gland, the thyroglossal duct.
23. Where is the lingual tonsil? (N58, N63, TG7-39)
The lingual tonsil is in the submucosa on the superior surface of the root of the tongue
just behind the sulcus terminalis. It is a collection of lymphoid nodules that give the
posterior one-third of the tongue its warty appearance.
24. Consider the motor and sensory (special and general) innervation of the tongue. (N62,
N126, TG7-39, TG7-90, TG7-94)
GENERAL
TASTE (SPECIAL
MOTOR
SENSATION
SENSATION)
Hypoglossal n. (XII)
ANTERIOR TWOLingual n. (V)
Chorda tympani (VII)
-- extrinsic and
THIRDS
intrinsic muscles
Glossopharyngeal n. (IX)
POSTERIOR
Glossopharyngeal
(includes vallate
ONE-THIRD
n. (IX)
papillae)
EPIGLOTTIC
Superior laryngeal Superior laryngeal n. (X),
REGION OF
n. (X)
internal branch
TONGUE
25. Read about the intrinsic muscles of the tongue. (N126, TG7-38)
These are all muscles with attachments entirely within the tongue. Like all true tongue
muscles (intrinsic and extrinsic), they are innervated by the hypoglossal n. (CN XII).
They are the superior longitudinal muscle, the inferior longitudinal muscle, the transverse
lingual muscle, and the vertical muscle. All are treated in more detail in the objectives
section (but the only thing that I think we need to be aware of according to the laboratory
manual is that intrinsic muscles, as a group, exist).
26. Consider actions of both intrinsic and extrinsic groups of muscles in moving the
tongue and changing the shape of the organ. (N53A, N53C, N59, N63, N68, N126, TG738, TG7-40)
The actions of the extrinsic muscles are covered in the objectives section. In addition, the
palatoglossus, which is not a true tongue muscle, assists in elevation of the tongue. The
intrinsic muscles assist in all of the actions of the tongue but are particularly involved in
deviations of the tongue from side to side. Note that extrinsic and intrinsic muscles
combine for all of the actions of the tongue. "In eating, the tongue forms itself into a
trough-like receptacle, conducts the food between the teeth for their tearing and crushing
actions, and prevents food from falling to the floor of the mouth. Finally it makes firm
pressure against the palate above and forces the mixed food and saliva into the
oropharynx" (W&B 276).
Dissector Answers - Eye
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Identify the prominent bony features of the orbit with included foramina and
fissures.
2. Describe the components of the eyelids with associated muscles, tarsal glands,
connective tissue fascia and conjunctiva.
3. Identify the extraocular muscles, their function and innervation.
4. Identify all sensory, motor and autonomic nerves of the orbit and trace their routes
to and within the orbit.
5. Identify branches of ophthalmic arteries and veins.
Learning Objectives and Explanations:
1. Identify the prominent bony featrues of the orbit with included foramina and fissures.
(N2, N11, TG7-03, TG7-57)
There are 7 bones that make up the orbit:

Frontal - entire roof of orbit. There are 3 prominent foramina to know in this
region - the supraorbital notch (superior margin) and the anterior and posterior
ethmoidal foramina (at junction of frontal/ethmoid bones). Nerves and vessels
pass FROM the orbit TO the nasal cavity through these foramina

Ethmoid bone - a very delicate bone in medial wall of orbit.

Maxilla - medial wall and much of floor. Infraorbital groove is a deep groove on
the orbital floor, where infraorbital n. lies. The anterior lacrimal crest is on the
medial margin. (note relation with sphenoid bone, info below)

Lacrimal - very small bone; gives a crest - posterior lacrimal crest; between the
post. and ant. crests is the fossa for the lacrimal sac (not to be confused with the
lacrimal fossa of the roof of the orbit, where the gland is located under the frontal
bone).

Zygomatic - lateral margin and the rest of the floor

Sphenoid - forms the apex; there are a number of openings:
1. medially: optic canal for optic n./ophthalmic a.
2. laterally: superior orbital fissure for a number of nerves (III, IV, V1, VI) &
superior ophthalmic v.; it separates the greater and lesser wings of this
bone
3. inferior orbital fissure between sphenoid and maxilla: through here brs. of
maxillary nerve and artery pass; also veins from deep face region pass
through here connecting with veins within orbit

Palatine - not very important; however, note below under bony orbit, its small role
in the floor of the orbit
Orbit (bony): pyramidal-shaped space, formed by seven bones of the skull - four walls
and an apex; medial walls are parallel and 2 cm apart, the space in between consists of
the ethmoidal air cells and sphenoid sinus; the lateral walls diverge at 45 degrees from
the medial walls, and left and right are 90 degrees apart; the margins of the orbital
aperture are strong; the bone of the margins is much heavier than that of the walls within
the cavity
Roof - orbital plate of frontal bone, and near the apex, lesser wing of the sphenoid bone;
concave, especially laterally where the lacrimal fossa accommodates the lacrimal gland;
the frontal sinus frequently extends over the roof of the orbit nearly to its apex
Lateral wall - formed in front by the zygomatic bone and behind by the greater wing of
the sphenoid bone; the lateral wall, stronger, separates the orbit from the temporal fossa
Floor - slopes upward toward medial wall; formed by orbital surface of maxilla,
supplemented laterally and anteriorly by the zygomatic bone and medially and posteriorly
by the palatine bone; near the middle of the floor is the infraorbital groove extending
forward from the inferior orbital fissure, ending in the infraorbital canal; the floor of the
orbit is a bony separation between the orbit and the maxillary sinus
Medial wall - nearly vertical; consists of frontal process of the maxilla, the lacrimal bone
and the orbital lamina of the ethmoid bone, and a small part of the body of the sphenoid
bone; anteriorly the medial wall forms only a thin partition between the orbit and the
ethmoidal air cells and sphenoid sinus
Openings - the principle openings of the orbit lie at the junction of its walls
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Optic canal - junction of roof and medial wall; transmits ophthalmic artery and
optic nerve (covered by meninges)
Superior orbital fissure - upper lateral angle at apex of orbit; transmits CN III, IV,
V1, VI, sympathetic fibers from cavernous plexus, and superior ophthalmic vein
Inferior orbital fissure - junction of lateral wall and floor; from apex of the orbit
2/3rds distance to base; accommodates structures which have only an indirect
relation to orbit, i.e., infraorbital nerve and artery, communication between
inferior ophthalmic vein and pterygoid plexus, and infraorbital & zygomatic brs.
of V2
Other fissures/openings
o Supraorbital notch/foramen
o Zygomatico-orbital foramen for zygomatico-orbital n. in lat wall
o Ant. & post. ethmoidal foramina
o Canal for nasolacrimal duct, leads inferiorly from lacrimal groove
Other features of the bony orbit
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anterior lacrimal crest: see maxilla bone
posterior lacrimal crest: see lacrimal bone
lacrimal fossa: depression on roof laterally to accommodate the lacrimal gland
anterior ethmoidal foramen: see frontal bone
posterior ethmoidal foramen: see frontal bone
optic canal: see sphenoid bone, and see below
superior orbital fissure: see below
inferior orbital fissure: see sphenoid bone, and see below
periorbita (orbital periosteum): fascia surrounding the orbit and its contents
2. Describe components of eyelids with: muscles, tarsal glands, connective tissue fascia
& conjunctiva. (N26, N81, N82, TG7-30, TG7-57, TG7-58A, TG7-58B, TG7-58C)
Orbicularis oculi m: sphincter m. of eyelids; the lacrimal portion of the orbicularis oculi
m. is associated with the posterior offshoot of the medial palpebral ligament; a small
fascicle of muscle fibers covers the deep surface of this band, arising from the posterior
crest of the lacrimal bone; passing behind the lacrimal sac, the muscle divides into two
slips for insertion into the medial parts of the tarsal plates of both lids ; fibers also attach
to the lateral wall of the sac, creating a suction action when the lids are closed
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palpebral part: arises from the medial palpebral ligament, makes up the muscular
layer of the eyelid; fibers run elliptically toward lateral palpebral raphe (where
muscle bundles of the two lids intermingle)
orbital part: surrounds the bony orbit
Palpebral fissure: opening of eye itself; slit between two eyelids, a.k.a. palpebrae
Lateral angle, canthus, commissure: lateral corner of eye
Medial angle, canthus, commissure: medial corner of eye; at this corner are the lacrimal
caruncle, semilunar fold
Lateral palpebral ligament: attach the lateral portion of the tarsal plates to the zygomatic
bone, deep to the raphe
Medial palpebral ligament: about 5mm long, arises from the frontal process of the
maxilla, anterior to the lacrimal groove; extends lateralward into the eyelid in front of the
lacrimal sac and divides; its parts continuous with the tarsal plates of the upper and lower
eyelids; an offshoot of the ligament leaves its posterior surface lateral to the lacrimal sac
and attaches to the posterior lacrimal crest of the lacrimal bone
Conjunctival sac
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palpebral conjunctiva: the part of the conjuctiva that lines the inside of the lid
bulbar conjunctiva: the part of the conjuctiva that covers the eyeball
fornix: reflection of the conjunctiva from the eyeball to the eyelid; a potential
space filled with nothing but tears; the lacrimal gland secretes tears and they fill
this sac; superior fornix directly receives tears from the lacrimal gland through
small ducts that empty from the deep lobe of the gland
Cornea: sclera, pupil, iris; the transparent cornea is dense, its surface is bulbar
conjunctiva, is nonvascular and it is richly supplied with sensory nn from the ciliary
nerves
Pupil: the central aperture of the iris; size is controlled by smooth muscle of the iris
Iris: thin, contractile membrane, having a central aperture, the pupil; within the loose
stroma of the iris are two involuntary mm: sphincter pupillae m. (same parasympathetic
innervation as the ciliary m.) and dilator pupillae muscle (sympathetic supply from
superior cervical ganglion, reach the eye from the cavernous plexus through the short
ciliary nn.); iris separates chambers of the eye, filled with aqueous humor
Lacrimal caruncle: mound of skin found at medial canthus (corner of eye)
Lacrimal lake: located in the medial canthus, collects tears as they distribute over eye
through blinking
Semilunar fold: the edge of the lacrimal caruncle narrows out to form a thin fold of skin
Lacrimal apparatus
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lacrimal papillae: slight elevations on the edge of the eyelids at the medial corner;
in each of these is a little opening or punctum
lacrimal puncta (pores): little openings in the lacrimal papillae; these openings
drain fluid from the lacrimal lake by sucking the tears into the lacrimal canaliculi.
The lacrimal fluid then passes through them into the lacrimal sac.
lacrimal gland: produces tears, fills conjunctival sac; uppermost lateral part of the
orbit, in the lacrimal fossa of the frontal bone; the gland is divided into superficial
and deep parts by the levator palpebrae superioris m; on the deep lobe there are a
number of small ducts that empty DIRECTLY into the superior conjunctival
fornix
lacrimal sac: tears sucked by lacrimal puncta from lake into canaliculi to the sac,
where they drain on through the duct into the inferior meatus of the nasal cavity
nasolacrimal duct: continuation of the lacrimal sac, extends downward and
slightly lateralward and backward to the inferior meatus of the nose; occupies the
nasolacrimal canal formed by the maxilla, the lacrimal bone and the inferior nasal
concha, but traverses the mucous membrane of the nose obliquely, so that its
opening is partially guarded by the lacrimal fold
Orbital septum: (the superior palpebral fascia in the upper lid and the inferior palpebral
fascia in the lower lid), continuous with the periosteum of the bones of the superior and
inferior margins of the orbit and ends in the anterior surfaces of the tarsal plates
Tarsal plates: dense fibrous plates of tarsofascial layer; inferior is narrower than superior;
they give support and form to the eyelids; semilunar in shape; straight edge is at the lid
margin; medially, tarsal plates are continuous with the bifurcated ends of the medial
palpebral ligament; laterally they attach to the zygomatic bone by the lateral palpebral
ligament, deep to the corresponding muscular raphe; embedded within, at the posterior
surface, are the tarsal glands
Tarsal glands: embedded in the posterior surface of the tarsal plate in each lid; vertically
arranged and parallel, they number ~30 in upper, a little less in lower; these glands
secrete an oily substance that waterproofs the palpebral margins, so tears don't seep over
the lid margins
Orbital sheath: when the optic nerve enters the orbit through the optic canal (sphenoid
bone), it brings with it a meningeal coat of dura, arachnoid, and pia mater; these cover the
nerve all the way to the back of the eyeball
Bulbar fascia: the fascia that covers the eye; forms a loose capsule within which the
eyeball can move in all 3 axes of rotation; the sheath is continuous with the muscle
sheaths that surround the various muscles of the eye; anchored to orbital margins via
check ligaments
Muscle sheaths: the fascia covering the eye muscles, continuous with the bulbar fascia,
and connects to the medial and lateral sides of orbit by check ligaments; this anchors the
bulbar fascia to orbital margins by check ligaments
Check ligaments: connect muscle sheaths to sides of orbit; anchors bulbar fascia to
orbital margins
Annulus: at apex of orbit, dense fascial ring, a.k.a. common ring tendon; surrounds both
the optic canal and 1/2 superior orbital fissure; the four rectus mm. arise from it
Summary of eyelid:
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movable folds capable of closing in front of the eye, providing protection - upper
lid is larger, more movable (due to having an elevator muscle - levator palpebrae
superioris)
the eyelid is composed of five layers
o skin: thin
o subcutaneous tissue: lax, scanty, rarely contains fat; anterior edge of lid
are cilia (eyelashes); cutaneous nn. of eyelid = brs of V1 and brs. of
infraorbital br. of V2; rich vascular supply
o muscular layer: mostly palpebral portion of orbicularis oculi m, arises
from med palb lig
o tarsofascial layer: an important plane of division in the eyelid between a
superficial zone continuous with subcutaneous tissues of face/scalp and a
deeper area continuous with space of the orbit; this layer consists of:
 tarsus: dense fibrous plate; embedded within are the tarsal glands
 orbital septum: membrane
o conjunctiva: lines inner surface of each eyelid (palpebral) and is reflected
over the anterior portion of the sclera and cornea of the eyeball as the
bulbar conjunctiva
3. Identify extraocular muscles, their function and associated innervation. (N84, N86,
N121, TG7-59, TG7-61B, TG7-62A, TG7-62B, TG7-63A, TG7-63B)
There are 7 extraocular muscles - 6 that move the eyeball and 1 elevator of the upper
eyelid. All except inferior oblique muscle are at the apex of the orbit and pass forward at
the sides of the eyeball. Of the 6 muscles that attach to the eyeball, 4 are straight (rectus)
and 2 are oblique.
Levator palpebrae superioris m.
As the uppermost extraocular muscle, it expands beneath the roof of the orbit and ends
anteriorly in a wide aponeurosis
Origin: above and in front of optic canal
Insertion: superficial fibers - upper border of the superior tarsus (smooth muscle/ superior
tarsal m.); deep layer of m. - ends in sup. fornix of conjunctiva
Innervation: III (sup. div.) Continuously active during waking hours except during
closing of the lids
Simple lowering of the upper lid is accomplished by decrease of levator activity, but
blinking is result of contraction of orbicularis oculi m.
Muscular annulus
Origin point for all 4 rectus muscles
Superior rectus m.
Elevates & Adducts (Up & In); rotates superior pole of eyeball medially
Origin: annulus
Insertion: sclera just posterior to cornea
Innervation: III (sup. div.)
Narrowest of rectus mm
Inferior rectus m.
Depresses & Adducts (Down & In) rotates superior pole of eyeball laterally
Very inferior part of orbit
Origin: annulus
Insertion: sclera
Innervation: III (inf. div.)
Medial rectus m.
ADducts eye ONLY
Origin: annulus
Insertion: sclera just posterior to cornea
Innervation: III (inf. div.)
Broadest of rectus mm.
Lateral rectus m.
ABducts eye ONLY
Origin: two heads - one on either side of sup orbital fissure; separated by the nerves and
the ophthalmic vein that enter the orbit through the fissure
Insertion: tendinous expansion into sclera behind the margin of the cornea
Innervation: VI
Longest of rectus mm.
Superior oblique m.
Depresses & Abducts (Down & Out); rotates superior pole of eyeball medially
Extreme medial upper part of orbit;
Origin: immediately above the optic canal, runs forward to trochlea, attached in the
trochlear fovea of the frontal bone
Insertion: sclera behind the equator of eye
Innervation: IV
Runs forward, enters J-shaped ring of dense connective tissue: trochlea
Inferior oblique m.
Elevates & Abducts (Up & Out); rotates superior pole of eyeball laterally
Origin: near orbital margin
Insertion: eyeball
Innervation: III (inf. div.)
The only muscle that takes origin close to the orbital margin (the other 5 extraocular mm.
take origin at apex); here it moves obliquely backward and inferior to attach to eyeball
Summary of Clinical Testing
Medial and lateral rectus can be tested by simply adducting and abducting the eye,
respectively, looking for discrepancies in the degree of motion to one side or the other.
For the obliques and superior and inferior rectus, think of situps. People do bent-leg
situps to prevent iliopsoas muscle from acting in trunk flexion, so that the six-pack
muscles get a better workout. By flexing the hip, iliopsoas is prevented from doing its
other action, trunk flexion.
Superior and inferior rectus can both adduct the eye in addition to elevating or depressing
the gaze. So, prevent them from doing their second actions by doing the first - adduct the
eye or turn the gaze inward toward the nose. Now the superior and inferior rectus are not
able to do elevation or depression (just like bent-leg situps), so only superior oblique can
depress the gaze, and only inferior oblique can elevate the gaze.
Turn the gaze outward, and now the oblique muscles are too short to do their other
actions of elevation and depression. Ask the patient to look up or down to test superior or
inferior rectus muscles.
4. Identify nerves and trace them to and from cavernous sinus. (N86, N104, TG7-60A,
TG7-60B)
The nerves of the orbit are the:
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3 motor nn. to its muscles (CN III, IV, VI) [LR6, SO4, AO3]
sensory ophthalmic division of CN V
optic nerve arises in the retina of the eye, the other nn. enter the orbit through the
sup. orbital fissure
Sensory
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optic n. (CN II)
ophthalmic n. (V1)
o frontal n. divides into the supraorbital n and supratrochlear n, which
supply upper eyelid, forehead and scalp
 supraorbital n.
 supratrochlear n.
o nasocilliary n.: sensory nerve to the eye, supplies several brs. to the orbit
 anterior ethmoidal n. - terminal br. of nasocilliary, supply mucous
membrane of the sphenoidal and ethmoidal sinuses and the nasal
cavities, and the dura of the ant. cranial fossa
 long cilliary nn. - brs. of nasociliary n., transmit afferent fibers
from the iris and cornea and some post-synaptic sympathetic fibers
to dilator pupillae
o lacrimal n.: arises in lat wall of cavernous sinus, passes to the lacrimal
gland, giving brs. to conjunctiva and skin of superior eyelid and providing
secretomotor fibers from zygomatic n. (V2)
Motor
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oculomotor n. (CN III): aside from supplying most ocular mm., it supplies
parasympathetic innervation to the sphincter pupillae m. of the iris and the ciliary
m. of accommodation; it has 3 nerve components: somatic efferent (motor),
general somatic afferent (to same mm), general visceral efferent (mm of iris and
ciliary body with a synapse in the ciliary ganglion)
o superior division: sup. rectus/ levator palpebrae superioris m.
o
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inferior division: proceeds forward in orbit below optic n.; medial rectus,
inferior rectus, inferior oblique & motor br. to ciliary ganglion
trochlear n. (CN IV): smallest of CN's, supplies only one muscle - the sup.
oblique; only CN that emerges from the dorsal aspect of the brainstem; most
superior nerve entering in superior orbital fissure; in orbit it is medial to frontal
nerve
abducens n. (VI): like CN IV, it supplies only ONE muscle: the lat. rectus m.;
enters the cavernous sinus by piercing the dura mater on the dorsum sellae of the
sphenoid bone, turning over a notch in the bone below the posterior clinoid
process; passing forward within sinus on lateral side of internal carotid a., enters
orbit through the lower potion of the superior orbital fissure; at apex of orbit,
passes between the two heads of origin of lateral rectus m., inferior to other nn. in
this location
Autonomic
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sympathetic
parasympathetic
o preganglionics from oculomotor (III)
o cilliary ganglion: located between optic nerve and lat. rectus m, ~1cm
from post limit of orbit; motor root from inf. br. of CN III, fibers
contained in this root synapse in ciliary ganglion; the sensory root of
ganglion is a br. of nasociliary n. of CN V1; the sympathetic root from the
cavernous plexus passes to the ganglion adjacent to the sensory root; the
nerve fibers of both the sensory and sympathetic roots pass through the
ganglion WITHOUT synapsing; 6-10 short ciliary nn. leave ant. part of
ganglion and course forward above and below optic nerve, to pierce the
back of the eyeball
o short ciliary - postganglionic parasympathetics to sphincter pupillae and
ciliary muscles of eyeball, postganglionic sympathetics to dilator pupillae
o postganglionic parasympathetics from pterygopalatine ganglion to
lacrimal glands; preganglionics from facial, CN VII, via greater petrosal
5. Identify branches of ophthalmic arteries and veins. (N85, N87, N70, TG7-62, TG7-73)
Ophthalmic a.: branch of the intracranial portion of the internal carotid, as it emerges
from the cavernous sinus; passes directly forward and enters orbit through optic canal,
below and lateral to optic nerve; curves across optic nerve toward medial side of orbit,
anteriorly; brs include: Central artery of the retina, Lacrimal, Short posterior ciliary,
Supraorbital, Long posterior ciliary, Posterior ethmoidal, Anterior ciliary, Anterior
ethmoidal, Medial palpebral, Supratrochlear (terminal branch), Doral nasal (terminal
branch), Muscular brs.
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central artery of retina (runs within optic nerve): is the first and one of the
smallest branches; arises close to the optic canal and pierces optic near at the
middle of its intraorbital course; accompanied central vein of retina; its brs on
retina are: superior nasal, superior temporal, and inferior nasal and inferior
temporal
superior ophthalmic v.: begins in nasofrontal vein, enters orbit through
supraorbital foramen (notch), after communicating with supraorbital vein; has
tributaries which correspond to upper branches of ophthalmic a, usually joined by
inf. ophthalmic vein at medial end of sup. orbital fissure; may leave head between
two head of lat. rectus or above the muscular cone; ends in cavernous sinus;
DOES NOT CONTAIN VALVES.
Review:
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cavernous sinuses: lie on either side of body of sphenoid, extend from sup. orbital
fissure (in front) to the apex of petrous portion of temporal bone (in back); formed
between the meningeal and periosteal layers of dura and trabeculae from each
layer cross space, giving it a reticular (cavernous) structure; for more on this
review item see page 325 in Woodburne and Burkel
anterior cranial fossa: limited behind by post borders of lesser wings of sphenoid
and groove for optic chiasma; floor is formed by orbital plates of frontal bone,
cribriform plate of ethmoid and lesser wings and fore part of body of sphenoid;
anterior midline is the crest of frontal bone leading to the foramen cecum, through
which emissary vein passes from nasal cavity to beginning of sup. sagittal sinus;
for more see page 319-320 WB.
Questions and Answers:
1. Define conjunctival sac. (N81, TG7-58)
See objective 2 above.
2. Define tarsal glands. (N81, TG7-58)
See objective 2 above.
3. What is the flow of lacrimal fluid across the eye? (N82, TG7-58)
Tears secreted from the lacrimal gland moves across eye via blinking, toward the medial
canthus and lacrimal lake; drained off by lacrimal canaliculi; empty into lacrimal sac,
then pass through nasolacrimal duct to inferior meatus of nasal cavity
*NOTE: when formed in normal amounts, the amount reaching nose evaporates; it is
when the amount is increased (by emotion or other causes) that it flows from the nose
**NOTE: the parts of the lacrimal apparatus are: lacrimal gland; lacrimal canaliculi;
lacrimal sac; nasolacrimal duct
4. Define orbicularis oculi m.: palpebral part vs. orbital part. What are differences? (N26,
TG7-30, TG7-57, TG7-58)
The orbital part of orbicularis oculi surrounds the bony orbit, while the palpebral part
extends into the lids.
5. What is the attachment of the medial palpebral ligament? (N81, TG7-57)
It attaches to the frontal process of the maxilla and extends into the eyelids to attach to
both tarsal plates.
6. Define layers of superior lid. (N81, TG7-58)
Skin, subcutaneous tissue, palpebral part of orbicularis oculi, tarsofascial layer (tarsal
plate attached to orbital septum, with tarsal glands embedded within plates), palpebral
conjunctiva.
7. What is the relationship of lacrimal gland to eyelid? (N82, TG7-58B)
The lacrimal gland lies superolaterally in the bony orbit, deep to the conjunctival fornix.
8. Define tarsal plate and attachments. (N81, TG7-57, TG7-58)
The tarsal plates are attached to the medial and lateral palpebral ligaments and the orbital
septum.
9. Define orbital septum. (N81, TG7-57)
The orbital septum is a fascial sheet extending from the orbital margins to the tarsal
plates within the eyelids.
10. Where does the lacrimal part of orbicularis oculi attach? (N26, TG7-57)
The lacrimal part of orbicularis oculi arises from the lateral wall of the lacrimal sac and
the bone posterior to it. It passes into the lids to insert on the tarsal plates.
10a. What is the action of the lacrimal portion of the orbicularis oculi muscle? (N26,
TG7-57)
The lacrimal portion of the orbicularis oculi muscle pulls backward and holds the eyelids
close against the eyeball. It also aids in dilating the lacrimal sac, creating a syphon-like
action during blinking.
11. What is the drainage to the lacrimal sac? (N81, N82, TG7-43, TG7-58)
Lacrimal puncta drain the lacrimal fluid through lacrimal canaliculi into the lacrimal sac.
12. What muscles does the trochlear n. (CN IV) supply? (N86, N121, TG7-80)
Trochlear nerve innervates superior oblique muscle, which acts around a trochlea or
pulley.
12a. How can you test the action of the superior oblique muscle? (N84, TG7-59)
To test the superior oblique muscle, the patient is asked, first, to direct the gaze medially
and then down. By turning the gaze medially, the inferior rectus is shortened and
prevented from performing its other action, turning the gaze down.
13. What is the distribution of anterior ethmoidal branch of the nasociliary nerve (V1)?
(N86, N42, TG7-45, TG7-63)
Supplies twigs to ant. ethmoidal air cells; supplies internal nasal branches to mucosa of
septum and nasal wall; ends as the external nasal br., supplies skin on lower half of the
bridge of the nose (more pg 297 WB).
14. Define parts of lacrimal gland. (N82, TG7-58)
The orbital part of lacrimal gland lies in the lacrimal fossa of the orbital plate of the
frontal bone. The palpebral part extends down into the lateral part of the upper lid by
wrapping around the lateral margin of the levator palpebrae superioris.
15. What is the relation of lacrimal gland to levator palpebrae sup. aponeurosis? (N82,
TG7-58)
The orbital part of the lacrimal gland lies superior to the aponeurosis, while the smaller
palpebral part passes around the lateral edge of the aponeurosis and beneath it.
16.What is the innervation to the two heads of the lateral rectus m.? (N86, N121, TG7-63,
TG7-86)
Abducens nerve (CN VI).
17. What are the relations of oculomotor and nasociliary nn. to optic n. and ciliary
ganglion? (N86, N121, TG7-63)
The inferior division of the oculomotor nerve sends a short motor root up to the ciliary
ganglion, which lies lateral to the optic nerve. The inferior division then passes anteriorly
along the lateral edge of the inferior rectus. Nasociliary sends a branch to reach ciliary
ganglion and then passes anteromedially superior to the optic nerve.
18. Define short ciliary nn. from ciliary ganglion to bulb. (N86, N121, TG7-62, TG7-79)
Short ciliary nerves carry postganglionic parasympathetics and sympathetics and sensory
fibers from the ciliary ganglion to the back of the eyeball.
18b. What does the superior ophthalmic v. drain into? (N85, N104, TG7-61, TG7-73)
Cavernous sinus through the superior orbital fissure.
19. What are the actions of extraocular mm (ant. view?) (N84, TG7-59)
Superior oblique - turns pupil down and out (abducts & depresses)
Inferior oblique - up and out
Superior rectus - up and in
Inferior rectus - down and in
Medial rectus - in
Lateral rectus - out
20. With clinical testing of the mm., what are their actions and innervation? (N84, TG759)
See chart and explanation above.
21. How is the sheath (meninges) of optic n. formed? (N87, TG7-64)
The meninges pass through optic canal with the optic nerve.
22. How far does the subarachnoid space extend? (N87, TG7-64)
To the back of the eyeball.
Dissector Answers - Ear & Nasal Cavity
Learning Objectives:
Upon completion of this session, the student will be able to:
1. Define the three parts of the ear and the function of each part.
2. Describe each of the four walls of the middle ear cavity and identify deeper
structures responsible for certain of their features.
3. Describe the structure and actions of the tympanic membrane, the auditory
ossicles, and the muscles of the middle ear.
4. Trace the course of the facial nerve through the temporal bone and give the origin,
course, and functional components of each of its intracranial branches.
5. Identify the auditory tube and explain its function.
6. Describe the maxillary nerve, its distribution and functional significance.
7. Describe the nasal cavity, its general morphology including walls, openings, nasal
septum, conchae, meatuses, and its general neurovascular supply.
8. List the paranasal sinuses and where each opens into the nasal cavity.
9. Describe the hard and soft palate.
Learning Objectives and Explanations:
1. Define the three parts of the ear, and the function of each part. (W&B pp 302-307;
N92, N93, N94A, N94B, TG7-65, TG7-68A, TG7-68B, TG7-70)
The three parts of the ear are: external ear, middle ear and internal ear.
Functions:
External ear: is comprised of the oval auricle and the external acoustic meatus. The
external acoustic meatus is a canal, approximately 2.5cm long, which leads from the
auricle to the tympanic membrane. The auricle is the cartilaginous portion of the outer
ear, attached to the skull by ligaments and muscles, and covered by skin.
Middle ear: includes the tympanic cavity proper, the space directly internal to the
tympanic membrane, and the epitympanic recess, the space above it. The middle ear is a
narrow cavity in the temporal bone where the energy of sound waves is converted into
mechanical energy through a chain of ossicles.
Internal ear: consists of the cochlea, for auditory sense, and a series of
intercommunicating channels, the semicircular ducts, the utricle and the saccule, for the
sense of balance and position. The internal ear provides the essential organs of hearing
and of equilibrium.
2. Describe each of the four walls of the middle ear cavity and identify the deeper
structures responsible for certain of their features. (N92, N94A, N94B, TG7-65, TG768A, TG7-68B)
Lateral wall: formed by the tympanic membrane which is set obliquely into the external
acoustic meatus and faces outward, downward and forward. The tympanic membrane has
three layers: 1) the outer surface is the modified skin of the external meatus 2) the
intermediate layer is composed of radial and circular fibers which provide strength for the
membrane and 3) the internal layer is composed of mucous membrane. The tympanic
membrane is one cm in diameter and has a fibrocartilaginous ring at the greater part of its
circumference which fixes it into the tympanic sulcus at the inner end of the external
acoustic meatus. Where the membrane lacks this ring, at its upper limit, the membrane is
termed the membrana flaccida. Membrana flaccida is one sixth the area of the total
membrane and lacks the fibrous stratum which provides rigidity. The other five-sixths of
the membrane, called the membrana tensa, has this strengthening fibrous layer. The head
of the malleus is attached to the fibrous layer on the inner surface of the membrane and
extends to a little below the center of the membrane. On N93, TG7-69A, TG7-69B, TG769C, TG7-69D, the head/handle of the malleus appears to make a projection into the
membrane along its course. The most indrawn point of the tympanic membrane is termed
the umbo. Additionally, the radial fibers which compose part of the intermediate layer of
the tympanic membrane, diverge from the handle of the malleus. The circular fibers are
more at the edge of the membrane.
Medial wall: composed mainly of the promontory which is a bony eminence formed by
the cochlea. The promontory is grooved because of branches of the tympanic plexus
which lie under its mucous membrane. There are two fossa in the medial wall, formed by
the oval vestibular window and the round cochlear window. The fenestra vestibuli
(vestibular window or oval window) lies above the promontory, and is an opening in the
medial wall which is actually closed in life by the stapes. The fenestra cochlea, or round
window, is below and behind the promontory and is another opening which is closed in
life, only this time by a membrane. This membrane yields to the surge of fluid in the
closed system of canals of the inner ear produced by the piston-like action of the
footplate of the stapes at the vestibular window. (WB 305) There are two prominences in
the medial wall. One is the prominence of the facial canal and lies above the vestibular
window. This carries the facial nerve and sometimes the bone over the facial nerve is
quite thin. The other prominence is the prominence of the lateral semicircular canal and is
the most superior in the lateral wall.
Anterior wall: divides the tympanic cavity and the carotid canal. The caroticotympanic
nerves from the sympathetic plexus on the internal carotid artery perforate the anterior
wall and join up with the tympanic plexus. The anterior wall is incomplete because at its
superior edge are the openings for both the auditory tube and the semicanal for the tensor
tympani muscle. These openings are separated by the septum canalis musculotubarii, a
very long name for a very thin shelf of bone.
Posterior wall: at the top of the posterior wall is the aditus ad antrum, the entrance to the
mastoid antrum, which is the common cavity in the mastoid bone into which the mastoid
air cells open. Below the entrance of the mastoid antrum is the fossa incudis, the part of
the posterior wall which receives the short process of the incus. Also below the aditus ad
antrum is the pyramidal eminence, a conical elevation of bone which juts forward from
the posterior wall in front of the vertical portion of the facial canal. The eminence is
hollow and its walls give rise to the stapedius muscle. A small branch of the facial nerve
goes through the stapedius muscle at the base of the pyramidal eminence.
[WB 305-306]
3. Describe the structure and actions of a) the tympanic membrane, b) the auditory
ossicles, and c) the muscles of the middle ear. (N93,N94A, N94B, N96, TG7-68, TG769A, TG7-69B, TG7-69C, TG7-69D)
a) Tympanic membrane: The structure of the tympanic membrane is described in some
detail in the description of the lateral wall of the middle ear cavity in Objective 2 above.
Sound waves travel through the external acoustic meatus and set the tympanic membrane
into vibration.
b) Auditory ossicles: The auditory ossicles are three small bones, the malleus, the incus
and the stapes. The three bones are united by true joints and form a lever system which
converts the vibrations in air impinging on the tympanic membrane into mechanical
energy to oscillate the footplate of the stapes in the vestibular window. This lever system
causes a decrease in amplitude but an increase in power of the piston-like action of the
stapes. Their fixation in space depends on the attachments of the malleus to the tympanic
membrane and of the stapes in the oval window and on ligaments which suspend the
bones from the walls of the cavity.
Malleus: Supposedly shaped like a hammer. Its handle, or manubrium, is attached firmly
to the upper half of the tympanic membrane. Its anterior process arises from the neck of
the malleus and projects forward toward the petrotympanic fissure, to which it is
connected by ligamentous fibers. Its head projects upward into the epitympanic recess.
The posterior aspect of its head receives the incus.
Incus: Supposedly resembles an anvil. Body of incus articulates with head of malleus.
Short process of incus extends backward into fossa incudis and is attached there by
posterior incudal ligament. The long process of incus descends vertically, parallel to
handle of malleus and articulates with the stapes.
Stapes: Is supposed to and actually does kind of look like a stirrup. Its head is hollow and
receives the end of the long process of the incus. The neck of the stapes is where the
stapedius muscle (described next) inserts. Two crura diverge from the neck (which
continues from the head) and then the crura are connected by a flattened oval plate, the
base of the stirrup. The base of the stirrup is attached to the margin of the vestibular
window ( or oval window) by ligamentous fibers. Additionally, the articulation between
the malleus and incus is a synovial joint, a saddle-shaped articulation more specifically.
And the articulation between the incus and the stapes is a synovial joint and more
specifically, a ball and socket joint.
c) Muscles of the middle ear: The tensor tympani muscle arises from the septum canalis
musculotubarii (that very thin shelf of bone in the anterior wall), the cartilaginous part of
the auditory tube and part of the greater wing of the sphenoid bone. The muscle is 2 cm
in length and seems to lie on the septum. Its tendon wraps around the end of the septum
(at the processus cochleariformis) to enter the tympanic cavity. It inserts into the handle
of the malleus at its root and acts to draw the handle of the malleus and the tympanic
membrane toward the medial wall. This action increases the tension and dampens the
vibrations of the membrane. The tensor tympani muscle is innervated by a twig of the
medial pterygoid branch of the mandibular nerve. The fibers of the stapedius muscle arise
from the hollow pyramidal eminence (part of the posterior wall.) The central tendon of
the stapedius muscle inserts in the posterior surface of the neck of the stapes. The
contraction of the stapedius muscle tilts the footplate of the stapes which tends to dampen
its vibrations. It therefore seems to serve a protective function. Remember from the
description of the posterior wall that a small branch of the facial nerve travels to the
stapedius muscle at the base of the pyramidal eminence.
[Woodburne & Burkel 305 to 306]
4. Trace the course of the facial nerve through the temporal bone and give the origin,
course, and functional components of each of its intracranial branches. (N86, N94A,
N94B, N97, N123, TG7-67, TG7-68A, TG7-68B, TG7-87)
The facial nerve is composed of two unequal roots; the larger motor root supplies all the
muscles of facial expression, the smaller root, the nervus intermedius, contains taste
fibers from the anterior 2/3 of the tongue, fibers of general sensation from the external
acoustic meatus, parasympathetic and visceral afferent fibers for the submandibular,
sublingual, lacrimal, nasal and palatine glands.
The two roots enter the internal acoustic meatus with the vestibulocochlear nerve (CN
VIII), and divide into branches. Facial roots pass lateralward in the meatus between the
cochlea and semicircular canals and at the lateral end of the meatus they fuse and form
the geniculate ganglion. The geniculate ganglion is the sensory ganglion of the facial
nerve. It is located at the abrupt bend taken by the nerve as it turns from the acoustic
meatus into the posteriorly directed facial canal.
Intracranial branches of the facial nerve: greater petrosal nerve, geniculotympanic nerve,
and chorda tympani.
The greater petrosal nerve arises adjacent to the geniculate ganglion, it passes a short
course in the bone, and emerges at the hiatus of the canal for the greater petrosal nerve,
into the middle cranial fossa. After passing forward between the dura mater and the
trigeminal ganglion, crossing the foramen lacerum lateral to the internal carotid artery,
the greater petrosal nerve unites with the deep petrosal nerve (a sympathetic branch of the
internal carotid plexus) to form the nerve of the pterygoid canal. Function: the greater
petrosal nerve provides parasympathetic innervation of the lacrimal, nasal and palatine
glands, and sensory from the soft palate.
The geniculotympanic branch passes from the ganglion to the lesser petrosal nerve (lesser
petrosal nerve is a continuation of the tympanic nerve, which is a branch of the
glossopharyngeal).
The facial nerve then enters the bony facial canal distal to the geniculate ganglion, which
passes posteriorly in the medial wall of the tympanic cavity above the vestibular window,
and then behind the window, turns nearly vertically downward along the posterior wall of
the cavity. The facial nerve emerges from the skull at the stylomastoid foramen. In its
downward course along the posterior wall of the cavity, the facial nerve gives off a
branch to the stapedius muscle, a branch to the auricular branch of the vagus nerve, and
the chorda tympani.
The chorda tympani arises 5 mm proximal to the stylomastoid foramen, turns sharply
upward and enters a canal in the bone which takes it into the tympanic cavity. The chorda
passes forward over the medial surface of the tympanic membrane and under its mucous
membrane, and leaves the tympanic cavity near the anterior border of the membrane.
This anterior opening leads to the petrotympanic fissure, which is how the chorda exits
the skull. Function of chorda tympani: taste from the anterior 2/3 of the tongue,
parasympathetic innervation to the submandibular and sublingual glands. (W&B 309,
240, 287)
5. Identify the auditory tube and explain its function. (N55, N65, N67, N92, N94A,
N94B, TG7-24, TG7-65, TG7-68A, TG7-68B)
The auditory (eustachian) tube is a communication between the nasal portion of the
pharynx and the tympanic cavity that allows for equalization of pressure on either side of
the tympanic membrane. It is located in the anterior wall of the middle ear, and is
comprised of bone (1/3 of the length) at the tympanic end, and cartilage (2/3 of it) on the
pharyngeal end. Through the mucous membrane of the tube the pharyngeal mucosa is
continuous with that lining the tympanic cavity and mastoid air cells, which allows
passage of infectious material to the middle ear and mastoid area (otitis media).
6. Describe the maxillary nerve, its distribution and functional significance. (N49, N122,
TG7-81, TG7-83A, TG7-83B, TG7-83C)
The maxillary division of the trigeminal nerve (Cranial Nerve V2) is entirely sensory. It
supplies cutaneous innervation to the midface, from lower eyelid to upper lip, via its
infraorbital nerve and branches of its zygomatic nerve, the zygomaticofacial and
zygomaticotemporal. The zygomatic nerve and its zygomaticotemporal branch also relay
the postganglionic parasympathetic fibers from the pterygopalatine ganglion to the
lacrimal gland. The maxillary division also supplies sensory innervation to the nasal
cavity and palate via the nasopalatine nerve (to nasal septum), posterior superior lateral
nasal branches, posterior inferior lateral nasal branches (from greater palatine), and the
greater and lesser palatine nerves (to hard and soft palate respectively). These nerves also
carry postganglionic parasympathetic fibers from the pterygopalatine ganglion to the
nasal and oral mucous glands. A small pharyngeal branch of the maxillary division
reaches the nasopharynx and sphenoid sinus. The maxillary division reaches all of the
upper teeth and gingiva via its posterior superior alveolar nerve (to molars) and its middle
superior alveolar (premolars) and anterior superior alveolar (canine and incisors)
branches of the infraorbital nerve.
7. Describe the nasal cavity, its general morphology including walls, openings, nasal
septum, conchae, meatuses, and its general neurovascular supply. (N37A, N37B, N37C,
N42A, N42B, N43, N44, N45, N46, N47, TG7-41, TG7-42, TG7-43A, TG7-43B, TG745AB, TG7-45CD)
Walls of the nasal cavity:




Roof - primarily the cribriform plate of the ethmoid bone.
Floor - hard palate formed by palatine processes of the maxillae and the
horizontal processes of the palatine bones
Medial wall - nasal septum
Lateral wall - inferior, middle, and superior concha project from the lateral wall.
Beneath each is a space or meatus - inferior meatus, middle meatus, and superior
meatus. Above and behind the superior concha is a sphenoethmoidal recess.
Openings: nostrils or nares open onto the face, and choanae open posteriorly into the
nasopharynx.
Nasal septum: anteriorly, the septum is cartilagenous; posteriorly, it is bony. The upper
bony septum is formed by the perpendicular plate of the ethmoid, which articulates below
with the vomer.
Meatuses:




inferior meatus - receives the nasolacrimal duct (conducting tears from the orbit)
anteriorly
middle meatus - the bulla ethmoidalis projects medially beneath the middle
concha, with middle ethmoidal air cells opening on its surface. Below the bulla, a
curved groove, the hiatus semilunaris, receives the frontonasal duct from the
frontal sinus anterosuperiorly. Posteroinferiorly, it receives the maxillary sinus.
Between these openings the anterior ethmoidal air cells empty into the hiatus.
superior meatus - receives the posterior ethmoid air cells
sphenoethmoidal recess - receives the sphenoid sinus
Nerve supply: Olfactory epithelium, containing olfactory nerves, is found in and near the
roof. Anteriorly, branches of the anterior ethmoidal nerve from ophthalmic division of
trigeminal nerve (CN V1) distribute. Lateral wall - posterior superior and inferior lateral
nasal branches. Nasal septum - nasopalatine nerve.
Blood vessels: Sphenopalatine artery supplies most of the nasal cavity via its posterior
lateral nasal branches and its septal branches. Branches of the anterior and posterior
ethmoidal arteries also reach the anterior and superior portions of the nasal cavity.
8. List the paranasal sinuses and where each opens into the nasal cavity. (N41A, N41B,
N41C, N52, N53, TG7-43A, TG7-43B, TG7-44A, TG7-44BC)
Frontal sinus: middle meatus via hiatus semilunaris
Maxillary sinus: middle meatus via hiatus semilunaris
Ethmoid air cells (small air spaces within the ethmoid bone):



anterior ethmoid air cells - middle meatus via hiatus semilunaris
middle ethmoid air cells - middle meatus via bulla ethmoidalis
posterior ethmoid air cells - superior meatus
Sphenoid sinus: sphenoethmoidal recess
9. Describe the hard and soft palate. (N63, N64A, N64B, TG7-23, TG7-24)
The hard palate is formed primarily by the palatine processes of the maxillary bones, with
the horizontal processes of the palatine bones forming the posterior third. The soft palate
stretches posteriorly. It is a fibromuscular septum that can be moved to close off the
nasopharynx.
Questions and Answers:
10. Consider the structure and functions of conchae. (N37A, N37B, N37C, N70, TG7-22,
TG7-43A, TG7-43B)
The concha are scroll-like in shape. Also called turbinates, they cause inspired air to be
turbulent so as to facilitate the warming and humidifying action of the mucous
membrane, whose surface area is increased by the conchae.
11. Consider drainage of sinuses and air cells. (N37A, N37B, N37C, N52, N53, TG743B, TG7-44A, TG7-44BC)
See above.
12. What is the primary function of the tensor veli palatini? (N68, N69, N72, TG7-24,
TG7-65)
The most important function of tensor veli palatini is to open the auditory tube by pulling
its lateral wall inferiorly. This flushes the middle ear cavity with fresh air, thereby
equalizing pressure within the middle ear.