DIGESTIVE SYSTEM I
I. Digestive system - General considerations
A. Digestive tract - general structure.
1. A hollow tube with lumen of variable diameter.
2. Extends from mouth to anus
3. The wall, starting with the esophagus, shows different
specializations along its length that relate to function of
various components of digestive tract.
4. Various glands (e.g. salivary glands )and organs (liver, gall
bladder, pancreas) are also components of this system.
5. The wall of most of the digestive tract consists of 4 major
layers, the a) mucosa, b) submucosa, c) muscularis externa
and d) adventitia or serosa. In the oral region, only the
mucosa is easily defined.
II. ORAL CAVITY
A. The oral cavity is lined with a keratinized or
nonkeratinized stratified squamous epithelium
depending on what region you’re in.
1. This epithelium is often called the mucous
epithelium.
2. The transition between the stratified keratinized
squamous epithelium of the skin and the stratified
non-keratinized squamous epithelium of much of
the oral cavity occurs at the lips.
3. The superficial (surface) cells of the nonkeratinized epithelium are nucleated (as opposed
to those of keratinized epithelium of skin which are
not) and have only a few granules of keratin in their
cytoplasm.
http://www.finchcms.edu/anatomy/histology/
organology/digestive/o_d_3.html
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_3.html
4. Below the stratified squamous epithelium is a layer of loose connective tissue, the lamina
propria.
a. This lamina propria shows some interdigitation with the stratified squamous epithelium of
the oral region as the dermis of the skin does with the epidermis.
b. It contains blood and lymph vessels, small glands, nerves and aggregations of
lymphocytes.
5. Together, the stratified squamous epithelium and
the lamina propria form the oral mucosa - No
muscularis mucosae
6. Sublingual and submandibular salivary glands lie
in tissues below the mucosa (this would be the
equivalent of the submucosa or sometimes below it).
7. There is no distinct boundry between the lamina
propria and the submucosa and no true muscularis
externa in oral region - what muscle there is will be
striated. No serosa/adventitia.
1
2
3
4
5
6
7
8
9
vestibule
hard palate
soft palate
uvula
palatoglossal arch
palatine tonsil
palatopharyngeal arch
posterior wall of oropharynx
pterygoid hamulus
1
frenulum of tongue
2
ridge formed by deep
lingual vein
3
sublingual fold
4
sublingual caruncle
5
opening of submandibular
duc
B. The roof of the mouth consists of soft and hard
palates.
1. The hard palate has an intramembranous bone
backing which is covered by a keratinized mucous
epithelium.
2. The soft palate has a core of skeletal muscle and is
covered by a non-keratinized mucous epithelium.
http://mywebpages.comcast.net/wnor/lesson10.htm
C. Tongue
1. The tongue consists of a mass of striated
muscle covered by a mucosa consisting of
a non-keratinized, stratified, squamous
epithelium and lamina propria in most
places.
a. The mucous epithelium is strongly
adherent to the muscle below
b. This is because the C.T.of the lamina
propria penetrates into spaces between the
muscle bundles.
2. Tongue muscle is striated and composed
of bundles that are oriented in 3 planes.
a. This sort of structure increases both the
potential stiffness and the mobility of the
tongue.
http://www.lab.anhb.uwa.edu.au/mb140/
3. The dorsal surface of the tongue can be divided into
two areas by a V-shaped boundary found in the
posterior dorsal tongue surface.
a. The dorsal surface of the anterior 2/3 of the tongue is
covered by various types of papillae. Beneath the
surface are serous and mucous glands.
b. The posterior 1/3, behind the V, is composed of small
bulges that contain lymphatic nodules.
* These include the lingual tonsils that consist of lymph
nodules surrounding a single crypt.
1
anterior 2/3rd of tongue
2
posterior 1/3rd of tongue
3
palatogossal fold
4
palatine tonsil
5
fungiform papillae
6
circumvallate papillae
7
sulcus terminalis
8
foramen cecum
9
foliate papillae
http://mywebpages.comcast.net/wnor/lesson10.htm
4. The type of papillae found (see below) depends on what part of tongue you look at.
5. Types of papillae found on the dorsal surface of the tongue.
a. Filiform papillae - have an elongated conical shape.
* These papillae have a keratinized surface, are the most numerous and are found
over the entire dorsal surface.
* There are no taste buds in the epithelium covering filiform papillae.
http://www.siumed.edu/~dking2/erg/GI064b.htm
http://www.lab.anhb.uwa.edu.au/mb140/
b. Fungiform papillae - these are mushroom shaped.
* There are far fewer fungiform than filiform papillae.
* They are found interspersed between the filiform papillae over the entire anterior dorsal
surface of the tongue.
* A few taste buds may be found in the epithelium covering these papillae.
http://www.finchcms.edu/anatomy/histology/organology/digestive/images/ff674.jpg
http://www.doctorspiller.com/oral-dental_anatomy.htm
http://www.iob.uio.no/studier/undervisning/histologi/section/014/index.php
http://anatomy.iupui.edu/courses/histo_D502/D502f04/Labs.f04/digestive%20I%20lab/s41.20x.ug.jpg
c. Foliate papillae - these are arranged as closely packed folds along the posterior lateral margins of
the tongue and are only common in young children.
* There are numerous taste buds in the epithelium covering foliate papillae.
* Serous glands drain through openings at their bases.
http://www.doctorspiller.com/oral-dental_anatomy.htm
http://img224.imageshack.us/i/68foliate2yf1.jpg/
d. Circumvallate papillae - these are extremely large circular papillae which have a flattened
surface that extends above the other tongue papillae. About 12 in number.
* Circumvallate papillae are distributed in the V region of the posterior dorsal surface of the tongue.
* Many taste buds can be found in the epithelium covering their lateral surfaces.
http://www.lab.anhb.uwa.edu.au/mb140/
6. A deep groove encircles the body of the
circumvallate papilla.
a. Serous (von Ebner’s) glands (serous) drain
into the base of this groove.
b. The flow of fluid from these glands serves to
wash surface of the papilla and clean materials
from taste buds so they are ready for new
gustatory stimuli.
c. Other serous and mucous glands in other
parts of oral region serve the same sort of
purpose for cleansing other types of papillae.
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.finchcms.edu/anatomy/histology/organology/digesti
ve/images/ff677.jpg
7. Taste buds
a. Oval multicellular structures
b. Cells surround a cavity that communicates
with the oral cavity via a small pore between the
apexes of the cells.
c. Dissolved substances enter the cavity
through this pore and come into contact with
the microvilli of gustatory cells (neuroepithelial
sensory cells) of the taste bud.
d. These chemical stimuli are transduced to an
electrical impulse that is transmitted through
afferent axons of cranial nerves 7, 9, and 10
that synapse on the basal portions of the neuroepithelial cells.
e. Action potentials travel along these axons to
the portions of the brain responsible for our
sense of taste.
http://www.esg.montana.edu/esg/kla/ta/tastebud.jpg
http://www.lab.anhb.uwa.edu.au/mb140/
f. Taste buds are composed of 3 cell types
* Gustatory (taste) cells
* Sustentacular (support) cells
* Basal cells - stem cells for replacement of gustatory cells
** gustatory cells live for about 7-10 days
g. Both gustatory and sustentacular cells have similar structure, i.e. long microvilli
that extend into the lumen of the taste bud.
http://www.esg.montana.edu/esg/kla/ta/tastebud.jpg
DIGESTIVE SYSTEM 1B
ADULT TOOTH STRUCTURE
TOOTH DEVELOPMENT
Teeth
1.
In adult humans there are 32 permanent
teeth.
2.
These are preceded during childhood by 20
deciduous teeth.
3.
The tooth lies in a bony socket, the
alveolus, that is covered my an oral mucosa
called the gingiva (gums) that consists of,
a. keratinized stratified squamous
epithelium
b. lamina propria of loose connective tissue
that lies directly adjacent to the bone of the
alveolus.
The tooth consists of two major parts,
a. the crown - the portion that
protrudes above the gum line.
and
b. the root - the portion that extends
into the alveolus.
Internally, the tooth consists of a layer of
dentin that surrounds a pulp consisting of
loose connective tissue, nerves and blood
vessels. In the dentin, directly adjacent to
the pulp is a layer of specialized cells
called odontoblasts - secrete organic
matrix that calcifies and forms the dentin.
Odontoblasts extend thin processes
(Tome’s fibers), along which the organic
matrix of the dentin is secreted.
Crown region
Dentin is covered by a layer of calcified organic
matrix - the enamel
a. Hardest substance in body
b. Formed by ameloblasts before tooth “erupts”
from socket
Lamina
propria
Root region
Dentin (mineralized organic matrix) surrounds the
pulp.
In the root region, the dentin is covered by
calcified organic matrix - the cementum - similar
to bone, but no haversian system
Between the cementum and the bone of the
socket lies the periodontal ligament - consists of
fibroblasts and associated collagen fibers with
glycosaminoglycans in between.
a.
forms cushion between tooth and bone
b.
Attaches tooth to bone - Sharpey’s fibers
(insert into bone and cementum)
http://www.usc.edu/hsc/dental/ohisto/Cards/per/02_bb.html
http://www.dental.pitt.edu/informatics/periohistology/en/gu0404.htm
Alveolar bone
http://www.iob.uio.no/studier/undervisning/histologi/section/043/index.php
http://www.iob.uio.no/studier/undervisning/histologi/section/043/index.php
Where the gingiva meets the tooth specialized epithelium - junctional
epithelium - binds epithelium to enamel.
•Junctional epithelium is non-keratinized stratified
squamous without “dermal” papillae
•Bound to enamel by cuticle (looks like extra thick
basal lamina - called epithelial attachment of
Gottlieb)
•Cells of junctional epithelium tightly attached to
cuticle by hemidesmosomes
•Between this attachment and the gumline is the
gingival sulcus. Lined by sulcular epithelium. This
is a non-keratinized stratified squamous
epithelium.
•When dentist probes around your teeth checking depth of sulcus.
•If too deep, indicates breakdown between
enamel and junctional epithelium - periodontal
disease
http://www.iob.uio.no/studier/undervisning/histologi/section/043/index.php
TOOTH DEVELOPMENT
http://en.wikipedia.org/wiki/Image:Molarsindevelopment11-24-05.jpg
There are a number of terminologies that are used to describe the
early development of teeth prior to the cap stage.
In some cases, there is disagreement about what a given term
represents (e.g. dental lamina, tooth bud).
The following description of tooth development tries to make sense
out of the available reference material I’ve been able to find;
however, be aware that you may see other terminologies used in
dental school.
24
1. Prior to the 6th week of gestation in human embryos, the
developing jaws are solid masses of tissue with little differentiation.
2. Tooth development begins during the 5th - 6th week of gestation.
25
3. The first indication is the appearance of a thickened plate of
epithelium (labial lamina = vestibular lamina) between the tongue
and the upper and lower jaw. This, and the following events occur in
both the upper and lower jaw.
4. This thickened epithelium spreads over the inner (oral) jaw surface.
5. An invagination (labial groove) forms in this thickened epithelium.
This becomes the vestibule that separates the lip or cheek from the
gum.
26
6. The labial (vestibular) lamina overlying the forming gums gives rise to the
dental lamina (dental ledge). Neural crest cells in the underlying mesenchyme
induce the vestibular lamina epithelium to grow into the surrounding gum tissue.
This forms a C-shaped band of tissue in the gums of the upper and lower jaw that
is called the dental ledge or dental lamina.
27
6. The labial or vestibular lamina overlying the forming gums gives rise to the
dental lamina. Neural crest cells in the underlying mesenchyme induce the
dental lamina epithelium to grow into the surrounding gum tissue. This forms a Cshaped band of tissue in the gums of the upper and lower jaw that is called the
dental ledge or dental lamina.
In regions where a tooth will form, a further ingrowth of the dental lamina forms
the tooth bud.
A - dental lamina; B - Mesenchymal neural crest
http://dentistry.ouhsc.edu/oral-histology/
7. In 10 distinct regions of each jaw, the cells of the dental ledge
proliferate rapidly by mitosis forming a cup-shaped structure called
the enamel organ that is surrounded by jaw mesenchyme. The
enamel organ remains connected to the vestibular or labial lamina by
the cord-like remains of the dental lamina.
8. Five enamel organs will develop on the right and left sides of both the
upper and lower jaw. These will form the child’s “milk” (primary)teeth.
Enamel
organ
http://dentistry.ouhsc.edu/oral-histology/
http://32teethonline.com/pedopage2.htm
9. The mesenchyme that fills the enamel organ cup will become the
dental papilla which eventually forms the dentin and the pulp of the
tooth.
10. The enamel organ and dental papilla are surrounded by a sheath of
connective tissue called the dental sac.
11. The entire structure is called the cap stage of tooth development.
A, Enamel organ; B, Dental lamina; C, Vestibular lamina; D, Dental Papilla; E, Dental sac
http://dentistry.ouhsc.edu/oral-histology/
30
12. The cap stage of tooth development continues to differentiate, forming the bell
stage. Concurrent with this, the successional lamina, that will form the
secondary tooth later in life, forms as a outgrowth of the remaining dental lamina.
13. This differentiation includes the enamel organ. As is the case for the optic cup,
the cup of the enamel organ consists of two adjacent layers of cells that result from
the formation of the cup. These are an inner layer of cells (adjacent to the dental
papilla) that is called the inner enamel epithelium and an outer layer of cells
(adjacent to the dental sac)called the outer enamel epithelium.
A - Inner enamel epithelium; B - Outer enamel epithelium; C - Stellate reticulum; D - Successional
31
lamina; E - Dental lamina; F - Dental papilla; G - Dental sac.
http://dentistry.ouhsc.edu/oral-histology/
14. The ectodermally derived tissue between these two layers forms a matrix of cells called
the stellate reticulum. This matrix is essentially a connective tissue with lots of
extracellular material (mainly mucopolysaccharides) between the cells.
15. The inner enamel organ epithelium will eventually differentiate into cells called
ameloblasts that will form the enamel of the tooth.
16. Neural crest cells in the dental papilla will form an epthelial layer directly adjacent to
the ameloblasts that will differentiate into cells called odontoblasts which will form the
tooth dentin.
17. The remainder of the dental papilla will form the dental pulp of the tooth.
A - Inner enamel epithelium; B - Outer enamel epithelium; C - Stellate reticulum; D - Successional
lamina; E - Dental lamina; F - Dental papilla; G - Dental sac.
32
http://dentistry.ouhsc.edu/oral-histology/
18. The lips of the cup that forms the enamel organ are called the cervical loop. This
structure consists of a portion of the inner and outer enamel epithelium at the region
where they join.
19. Research indicates that the inner enamel epithelium portion of the loop is a source of
stem cells for the developing ameloblasts (the cells that produce the tooth enamel). The
cervical loop will partially degenerate as the root of the tooth develops and will become
the Epithelial Root Sheath of Hertwig. In species with continuously growing teeth (e.g.
rodents), the cervical loop is retained through adulthood, thus emphasizing its importance
in providing stem cells to produce ameloblasts for enamel formation.
A - Inner enamel epithelium; B - Outer enamel epithelium; C Stellate reticulum; D - Successional lamina; E - Dental lamina;
F - Dental papilla; G - Dental sac.
A, Cervical loop; B, Inner enamel
epithelium; C, Outer enamel
epithelium; D, Stratum intermedium;
E, Stellate reticulum
33
http://dentistry.ouhsc.edu/oral-histology/
20. As differentiation of the inner enamel epithelium proceeds, cells called
preameloblasts differentiate from the epithelium, adjacent to the dental papilla.
These cells induce neural crest cells in the adjacent dental papilla to differentiate into
preodontoblasts.
A - Inner enamel epithelium; B - Outer enamel epithelium; C Stellate reticulum; D - Successional lamina; E - Dental lamina;
F - Dental papilla; G - Dental sac.
A - Preameloblasts; B - Preodontoblasts; C
- Stellate reticullum; D - Dental papilla
34
http://dentistry.ouhsc.edu/oral-histology/
21. The preodontoblasts become odontoblasts as they begin to secrete predentin
(which will become dentin). The predentin blocks nutrients from moving from the pulp to
the preameloblasts. This causes the preameloblasts to become ameloblasts and begin their
secretion of enamel. The odontoblasts and ameloblasts move away from each other as the
dentin and enamel layers increase in thickness.
22. As this begins to occur, the developing tooth enters the crown stage.
1 - Ameloblasts; 2 - Enamel; 3 - Dentin; 4 - Odontoblasts; 5 - Pulp
A - Odontoblasts; B - Predentin; C - Ameloblasts;
D - Dentin; E - Enamel
http://www.histol.chuvashia.com/atlas-en/digestive-05-en.htm
http://dentistry.ouhsc.edu/oral-histology/
35
23. Once enamel depostion is completed and the crown is fully formed, the enamel
organ collapses and the cells form a sheath called the reduced enamel epithelium
that covers the crown of the tooth until eruption. This epithelium may be considered
stratified and consists of the ameloblast layer, called mature or protective
ameloblasts at this point, and the cellular remnants of the rest of the enamel organ.
A - Reduced enamel epithelium; B - Maturative/protective ameloblasts; C - Capillary
36
http://dentistry.ouhsc.edu/oral-histology/
24. Once the formation of the crown is completed, the root forms. The inner and outer
enamel epithelial layers of the cervical loop region continue to grow toward the future
base of the tooth. These tissues form the epithelial root sheath of Hertwig.
25. The root sheath induces the formation of additional odontoblasts that form the
dentin of the root.
26. The central region of the root is called the radicular pulp cavity.
D
C
B
F
E
Epithelial root
sheath of Hertig
A
A - Epithelial diaphragm; B - Radicular pulp cavity; C - Dentin; D
- Enamel space; E - Alveolar Bone; F, Root
37
http://dentistry.ouhsc.edu/oral-histology/
26. The leading edge of the root sheath turns inward toward the root of the tooth and
forms the epithelial diaphram.
D
C
B
F
E
A
A - Radicular pulp cavity; B - Dentin; C Dental sac; D - Point at which epithelial root
sheath begins to disintegrate; E - Epithelial
diaphram
A - Epithelial diaphragm; B - Radicular pulp cavity; C - Dentin; D
- Enamel space; E - Alveolar Bone; F, Root
http://dentistry.ouhsc.edu/oral-histology/
38
27. Once the root odontoblasts have formed and are secreting dentin, the epithelial
root sheath begins to break down. At this time, cells from the dental sac that
surrounds the developing tooth migrate to the surface of the newly formed dentin and
become cementoblasts. These cells secrete the cementum layer that acts as an
attachment region between the root of the tooth and the peridontal ligament. The
periodontal ligament binds the root of the tooth to the bone of the alveolar socket.
A, Enamel organ; B, Dental lamina; C, Vestibular lamina; D, Dental Papilla;
E, Dental sac
A - Cementoblasts; B - Odontoblasts; C - Predentin
http://dentistry.ouhsc.edu/oral-histology/
39
29. As the epithelial root sheath degenerates it leaves small groups of cells that are in the
peridontal ligament around the root and that are called epithelial rests.
A - Epithelial rests; B - Mantle dentin; C - Globular dentin; D - Circumpulpal dentin
40
http://dentistry.ouhsc.edu/oral-histology/
30. Once the tooth is fully formed it is ready to undergo eruption. This process occurs after
birth and involves active movement of the tooth such that it penetrates the gum tissues and
extends above them.
31. It is likely that there are a number of factors involved in eruption. While there is no
consensus on the cause of tooth eruption, there seems to be agreement that root growth,
alveolar bone remodeling, and possibly the peridontal ligaments are involved in this process.
32. In humans, eruption of the milk (primary) teeth generally begins in the second month and
continues until the end of the second year.
33. Thirty-two permanent (secondary) teeth develop, 20 from the successional laminae of the
milk teeth and 12 from additional tooth buds along the dental lamina in same manner as
primary teeth. The primary teeth will be replaced and 12 additional teeth will be added to the
dentition.
34. Twenty-eight of the secondary
teeth erupt between the ages of 6
and 13 years. The four wisdom
teeth may erupt between 17 and
21 years; however, they often
remain impacted.
41
http://www.uic.edu/classes/orla/orla312/Teeth%20in%20Function%3B%20Life%20History%20of%20Teeth.htm
DIGESTIVE SYSTEM IC
Esophagus and Stomach
The wall of the digestive tract
starting with the esophagus.
A. The wall of the digestive tract (starting with the
esophagus) can be divided into 4 layers,
1. Mucosa - Mucous layer
a. epithelial lining
b. lamina propria of loose connective tissue - includes blood,
lymph vessels, and sometimes glands.
c. Smooth muscle region called muscularis mucosae lies
below the lamina propria.
http://arbl.cvmbs.colostate.edu/hbooks/
pathphys/digestion/basics/gi_microanatomy.html
d. The mucosa forms selectively permeable barrier to the
contents of digestive tract. In the stomach and small
intestine, it takes part in both the digestion of food and in the
small intestine, the transport of nutrients into the body.
e. The movements caused by the muscularis mucosae act to
increase contact of the mucosa epithelium with food in the
digestive tract.
f. glands may be present in lamina propria.
http://www.meddean.luc.edu/lumen/
MedEd/Histo/HistoImages/hl8-04.jpg
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.leeds.ac.uk/chb/pcd2130/Img0014.jpg
1. Mucosa
f. The lamina propria is often rich in macrophages. Aggregations of “free” lymphoid
cells and lymph nodules may also be present
* This area can be said to act as a barrier to bacterial invasion.
* These cells in lamina propria (and also the submucosa) act to help prevent
spread of infectious organisms into the body via the digestive tract.
http://www.finchcms.edu/anatomy/histology/organology/lymphoid/o_l_8.html
2. Submucosa
http://www.leeds.ac.uk/chb/pcd2130/Img0014.jpg
a. Another layer of loose C.T. with many blood and lymph vessels that lies just below the
muscularis mucosae.
b. This layer also contains nerve plexuses each called a Meissner's plexus
(parasympathetic).
c. Glands and Lymph nodules may also be present in this layer.
http://www.leeds.ac.uk/chb/pcd2130/Img0014.jpg
3. Muscularis externa - smooth muscle layer
a. In most regions, circular and longitudinal bands of smooth muscle.
b. closest to lumen - circular smooth muscle.
c. furthest from lumen = longitudinal smooth muscle.
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Oral/Oral.htm
http://www.meddean.luc.edu/lumen/
MedEd/Histo/HistoImages/hl8-30.jpg
3. Muscularis cont.
d. C.T. lies between these two layers
e. A myenteric (Auerbach's) nerve plexus and blood and lymph vessels are present in this layer
of C.T. between the two muscle layers (sympathetic and parasympathetic components).
f. Note - while the circular and longitudinal muscle layers are responsible for gross movements
of the digestive tract, we shouldn't forget that the muscularis mucosae causes movements of
the mucous layer that are independent of the rest of the digestive tract.
g. The longitudinal, circular and oblique smooth muscle layers of the stomach
undergo relatively slow rhythmic contractions that act to mix ingested food with
various stomach secretions and also move the food through the digestive tract.
h. These muscles can also respond to adverse conditions with very strong and
rapid contractions. (Often seen at frat parties.)
4. Serosa or adventitia
a.
Thin layer of loose C.T.
b.
Around most of the esophagus it is
an adventitia - blends with
surrounding tissue
c.
In peritoneal cavity, it is a serosa
covered externally by a simple
squamous epithelium.
d.
The simple squamous epithelium is
a continuation of the lining of the
peritoneal cavity - mesothelium
e. This layer is rich in blood and lymph
vessels as well as adipose cells
http://www.leeds.ac.uk/chb/pcd2130/Img0014.jpg
III. Esophagus
A. Basically a muscular tube that transports
food from mouth to stomach.
B. Lining same as in much of the oral cavity nonkeratinized stratified squamous epithelium.
C. Layers same as general digestive tract as
outlined above.
1. mucosa
a. epithelium
b. lamina propria
c. muscularis mucosae
2. submucosa
3. muscularis externa
a. inner circular muscle
b. outer longitudinal muscle
4. adventitia or serosa
D. Specializations of esophageal
tissues
1.
Tubuloacinar mucus secreting
glands called esophageal glands
proper are present in the
submucosa. Their ducts extend to
the esophageal lumen.
2.
Small branched mucus secreting
glands are also sometimes found in
the lamina propria near the
stomach. These are called
esophageal cardiac glands.
http://www.georgetown.edu/dml/educ/micro/gastro/3.htm
3.
The muscular layer of the
esophagus changes from
striated muscle near mouth, to
smooth muscle near stomach.
Why would this be the case?
4. A serosal layer with a simple squamous epithelium as its outermost
component is only found in the peritoneal cavity, below the diaphragm
and near the stomach. The rest of the esophagus has an adventitia outer layer of loose C.T. that blends with surrounding tissues.
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_27.html
http://education.vetmed.vt.edu/Curriculum/VM8304/lab_companion/Histo-Path/VM8054/LABS/Lab18/EXAMPLES/Exesoph3.htm
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_34.html
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_27.html
IV. Stomach
A. There are 3 major regions of the stomach,
each with a different histologic structure.
1. The cardia - cardiac stomach
2. The body (corpus) and fundus
3. The pylorus - pyloric stomach
http://www.lab.anhb.uwa.edu.au/mb140/
B. The inner surface of the stomach is thrown into
folds called rugae that include both mucosa and
submucosa.
1. The mucosa of the rugae is also folded. These folds form
invaginatoins, such that the basal areas of the invaginations
penetrate into mucosal lamina propria.
2. The upper portion of these invaginations in the mucosa are
called the gastric pits - foveolae gastricae.
a. The epithelial lining of the the pits and general surface area
of the stomach consists of simple columnar epithelium of
mucous secreting cells in all parts of the stomach.
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/
digestion/stomach/anatomy.html
3. The gastric glands of the stomach connect to the bottoms of
the gastric pits. The cellular structure of these glands is
different in the different parts of the stomach.
http://www.finchcms.edu/anatomy/histology/organology/digestive/images/ff746.jpg
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.lab.anhb.uwa.edu.au/mb140/
C. Cardiac stomach
1. A narrow circular region where esophagus
connects to stomach.
2. Mostly simple, unbranched, slightly coiled,
tubular cardiac glands in lamina propria - produce
mostly mucous.
3. Cell types present
a. mucous secreting cells
b. lysozyme secreting cells
c. enteroendocrine cells
d. a few parietal cells
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_36.html
http://www.lab.anhb.uwa.edu.au/mb140/
Cardiac Stomach
http://www.med.uiuc.edu/histo/large/atlas/objects/804.htm
D. Body (corpus)and fundus
1. Has branched, tubular gastric glands.
2. Each gastric gland is divided into 3 regions
a. isthmus
b. neck
c. base
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_36.html
http://www.lab.anhb.uwa.edu.au/mb140/
Gastric glands of fundus and body of stomach - structure
3. Five cell types are present in gastric glands of the
body and fundus
a. Isthmus mucous cells - present in isthmus.
* Similar to mucous secreting epithelial cells of gastric
pit region.
* Secrete neutral mucus that protects surface from
acid.
http://www.finchcms.edu/anatomy/histology/
organology/digestive/images/ff746.jpg
http://www.meddean.luc.edu/lumen/MedEd/Histo/HistoImages/hl8A-41.jpg
http://www.finchcms.edu/anatomy/histology/organology/digestive/o_d_36.html
b. Neck mucous cells
•
May be present in clusters in neck of
gastric gland (also found in other regions of
gland), secrete acid glycoprotein mucus.
•
Irregular in shape with basal nucleus.
•
Thought to be stem cells for other cell
types in the gastric glands
http://wbiomed.curtin.edu.au/teach/humanbiol/hb134/134hist/stomh.htm
c. Parietal (oxyntic) cells
* Most present in upper half of gland. Fewer
in basal portion of gland.
* These are rounded or pyramidal cells with
spherical nucleus and eosinophilic
(acidophilic) cytoplasm.
* These are the cells that produce
hydrochloric acid.
http://www.finchcms.edu/anatomy/histology/
organology/digestive/o_d_36.html
* When examined with EM, deep
invaginations of plasmalemma into
cytoplasm can be seen that form intracellular
canaliculi. Lined with microvilli.
* Large number of mitochondria and a
descrete golgi apparatus are present near
the base of each cell.
* There are NO SECRETORY GRANULES.
http://www.finchcms.edu/anatomy/histology/organology/
digestive/images/ff758.jpg
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.lab.anhb.uwa.edu.au/mb140/
* Resting cell and actively secreting cell have
different structure.
** In the resting cell there are many
tubulovesicular structures that can be seen
below the plasmalemma in the apical region.
** In the active cell, the tubulovesicular
structures fuse with the plasmalemma to
form many microvilli in the canaliculi and
thereby increase the surface area through
which HCl can be actively transported into
lumen of canaliculi.
*Both neural and hormonal factors cause
secretion by these cells.
http://www.finchcms.edu/anatomy/histology/organology/digestive/images/ff758.jpg
d. Chief (zymogenic) cells (basophilic)
* Predominant basally in glands.
* Typical protein synthesizing and
secreting cell structure.
* Granules (membrane bound vesicles)
of inactive enzyme pepsinogen in
cytoplasm.
* When inactive pepsinogin is released
into acidic environment of stomach it is
activated.
* Forms proteolytic enzyme pepsin.
* Also, some lipase is secreted.
http://www.finchcms.edu/anatomy/histology/organology/diges
tive/o_d_36.html
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.meddean.luc.edu/lumen/MedEd/Histo/Hi
stoImages/hl8A-43.jpg
http://www.meddean.luc.edu/lumen/MedEd/Histo/HistoImag
es/hl8A-45.jpg
e. Enteroendocrine cells - hormonal
Amine Precursor Uptake and Decarboxylation (APUD)
cells, Argentaffin cells (old terminology)
•
There are a number of different types of these
cells.
•
Granules of secretory material collect at base
of cell and are released into underlying tissue.
•
Have hormonal function.
•
At least one kind (Argentaffin cell)releases
hormone 5-hydroxytryptamine (5-HT) also called
serotonin
•
5-HT stimulates the activity of smooth muscle
and can greatly increase the movements of the
muscle layer of the stomach.
•
http://www.finchcms.edu/anatomy/histology/organology/digestive/i
mages/enteroendocrine.gif
(Actually, this is an intestinal gland)
http://www.meddean.luc.edu/lumen/MedEd/Histo/HistoImag
es/hl8A-50.jpg
Also found in intestinal glands.
Enteroendocrine cells might be
considered a sort of diffuse endocrine
gland.
E. Pylorus
1. Has deep, branched, gastric pits that connect to
pyloric glands that have similarities in structure to
glands of both the cardiac and body/fundic portions of
stomach.
2. These glands secrete lysozyme (into gland lumen)
and gastrin (into surrounding tissues - enteroendocrine
cells).
a. Gastrin is a hormone that stimulates the secretion of
HCl by parietal cells that are mostly in body and fundus
of stomach.
http://www.lab.anhb.uwa.edu.au/mb140/
http://www.finchcms.edu/anatomy/histology/organology/diges
tive/images/ff765.jpg
F. Cells of epithelial lining of stomach are
constantly being replaced.
G. The muscle layer of the stomach has 3 sub layers
instead of 2.
1. This is accomplished by mitotic activity of
cells in neck regions of gastric glands (neck
mucus cells).
1. External muscle sublayer is longitudinal.
2. Cells move from mitotic regions in two
directions,
3. Inner muscle sublayer is oblique.
a. Upward to replace the columnar mucous
secreting cells*.
2. Middle muscle sublayer is circular.
H. Serosa
* Replacement of these cells occurs every 5
days.
b. Downward to replace cells of gastric gland
epithelium, e.g. chief cells and parietal cells**.
** This replacement is relatively slow.
http://www.finchcms.edu/anatomy/histology/organology/digestive/images/ff758.jpg