1. Layers of the wall of the alimentary canal
1. Tunica Mucosa: innermost layer which surrounded the lumen, composed from:
• Epitheliails mucosa (epithelium)
• Lamina properia (loose connective tissue)
• Muscularis mucosa (two-three layers of smooth muscle fibers).
2. T. Submucosa: C.T. supports mucosa with blood &lymphatic vessles and nerve.
3. T. Muscularis: Inner circular and outer longitudinal layers of smooth muscle.
4. T. Adventitia or serosa: Mesothelium (simple squamous epithelium).
Esophagus
long muscular tube extended from pharynx to the stomach.
T. Mucosa: (epithelium) stratified squamous epithelium non keratinized . (L. properia) LCT. (Muscularis M.) Single layer of longitudinally Smooth muscle.
T. Submucosa: C.T. with esophageal glands (upper & lower parts).
T. Muscularis: inner circular &outer longitudinally muscle layers, in upper one middle third of esophagus these consist of skeletal muscle in rest part its completely smooth muscle.
T. adventitia: its brous C.T. to the diaphragm after that it is serosa.
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2. STOMACH Histologically divided into two types.
The stomach is a sac-like dilation of G.I.T. just caudal to the diaphragham, between esophagus and duodenum , receives food from esophagus and delivered its contents into duodenum.
Anatomically divided into several regions:
Cardiac region(near the esophagus).
Fundic region (expanded blind middle region ).
Pyloric region(near the duodenum).
Histologically divided into two types.
Non glandular stomach (Rumen, Reticulum, and Omasum) in (ruminants).
Glandular stomach (abomasum and simple stomach).( carnivores, equine)
The mucosa and submucosa of empty stomach are thrown into folds, known as rugae that disappear in the distended.
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3. Non glandular compartment
1. Rumen:
presents of ruminal papillae. These papillae are long in the blind sac of rumen and absent on the pillars. Their function is to increased the absorbing surface.
T. mucosa Epithelium is stratified squamous keratinized (thin). Lamina properia: D.I.C.T.
Muscularis mucosa: absent.
T. submucosa: loose connective tissue.
T. Muscularis: two-three layers of smooth muscle
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4. 2. Reticulum: 3.Omasum: T. mucosa:
is a continuation of rumen ,it is similar to the rumen in both
function and structure, and the differences between both
parts in the following :
T. mucosa: Epitheliails: the reticular has short folds which
subdivided into primary, secondary and tertiary folds. Lined
with same epithelium of rumen.
3.Omasum:
the omasal mucosa is leaf-like primary, secondary
and tertiary folds.
T. mucosa:
Epitheliails like in other parts.
Lamina properia is DICT ,
Muscularis mucosa two layers extended into folds.
T. Submucosa:
is composed from loose connective tissue.
T. Muscularis:
two layers, the inner layer extends between the two
layers of muscularis mucosa and into the folds.
T.serosa: as in other parts
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5. Simple stomach Divided into: 1. Non glandular portion:
This portion lined with stratified squamous keratinized epithelium underlined with properia of DICT .
2. Glandular portion ( including abomasum):
T.mucosa: presents the gastric pits (foveolae), at the bases of which the opening of gastric glands.
Epitheliails mucosa is simple columnar epithelium occasionally goblet cells are found toward the gastric pits the epithelium cells decreased in size and are cuboidal.
Lamina properia composed of gastric glands (simple tubular branched gland) which divided into three regions (neck, body, and Fundic ) containing following types of cells:
1. Mucous neck cells: located along surface lining cells , it produce mucous which protects the stomach.
2. Parietal cells (oxyphilic) found numerously in cardiac and few in pyloric regions of stomach produce HCL .
3. Diffused Endocrine system (DES) group of cells that produce hormones such as gastrin, somatstatine, and cholecystokinin.
4. Argentaffin cells.
5. Chief cells (zymogene cells) are numerously in the Fundic region of gland , it produce enzymes (pepsinogen , rennin, and lipase),these cells are found in pyloric region.
Note: the Fundic region has all types of above cells.
Muscularis mucosa compose of two-four layers of smooth muscle fibers.
T. Submucosa: is loose connective tissue without glands and has meissners plexuses.
T.Muscularis: three layers inner oblique layer, middle circular layers, and outer longitudinal layer.
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