Glandular Stomach
- true stomach
- includes ruminant abomasum
- has 4 parts
What are the 4 parts of the grandular stomach?
- cardia = transitional zone between esophagus and stomach
- fundus
- body
- pylorus = funnel shaped region opens into SI
Where is gastric acid produced?
Fundus and Body of Stomach
T/F: The glandular stomach shows all the layers of the GI tract.
True
Rugae
- temporary folds in mucosa and submucosa of glandular stomach
- they flatten out when the stomach fills with food
Mucosa of glandular stomach
- epithelium = simple columnar (mucus secreting)
- epithelium invaginates deeply into lamina propria = forms gastric pits
- invagination depths vary with different regions
- cells lining surface = surface mucous cells
- gastric glands open into gastric pits
Cardiac Region of Glandular Stomach
- most extensive in pigs; minor in other species
- transition from stratified squamous to simple columnar epithelium
- gastric (cardiac) glands usually lined by mucus-secreting cells
- gastric pits are 1/3 of entire lamina propria (medium depth)
Fundic Region of Glandular Stomach
-gastric pits are about 1/4 or less of lamina propria (relatively shallow)
How many parts are in the gastric (fundic) gland?
What are they?
4
- Isthmus = opening of gland into pit above it
- Neck = constricted area near isthmus
- Body = main tube
- Base = dilated adenomere
5 types of cells in fundic region
- chief (zymogen) cells
- parietal (oxyntic) cells
- mucus neck cells
- enteroendocrine cells
- germinal cells
Chief Cells
- most numerous in lower region of gland
- foamy or lacy appearance
- stain light blue with H and E stain d/t RER
- pyramid-shaped with a basally positioned round nucleus
- apically positioned secretory granules (zymogen granules) present in fasted animals
Secretions of Chief Cells
- pepsinogen = converted to pepsin, a proteolytic enzyme in acidic environment
- Rennin in young animals = curdles milk by coagulating casein
- gastric lipase
Parietal Cells (Oxyntic Cells)
- bright-staining eosinophilic cytoplasm d/t mitochondria
- large cells scattered throughout gland from neck to base
- “wedged” between chief cells
- spheroidal shaped with round nucleus
- contain intracellular canaliculi that extend from apical plasma lemma into cytoplasm
- canaliculi are occluded by many microvilli
What do parietal cells produce?
What stimulates the production of this product?
HCl
Stimulated by:
- cholinergic nerve endings
- gastrin
- histamine
Mucus Neck Cells
- lines neck of gland
- interspersed among parietal cells
- Mucoid product is different than that of the surface mucus cells:
- less viscous than surface lining mucus
- contain acidic glycosaminoglycans
-protection from hydrolytic activity of HCl
Enteroendocrine Cells
- endocrine/paracrine cells within enteric epithelium
- not limited to GI tract, but scattered all over body among epithelial cells
- stains with silver and chromium stains
- Examples in stomach
- G cells secrete gastrin
- D cells secrete somatostatin
- EC cells secrete seratonin and substance P
Germinal Cells
- stem cells
- found in gland neck and bottom of pits
Pyloric Region
- gastric pits are 1/2 of lamina propria (deepest pits of all regions)
- histologically similar to cardiac gland
- contains muscular sphincter in most species at the gastroduodenal junction
