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Stomach Mucosa

Page history last edited by PBworks 16 years, 3 months ago

Stomach Mucosa - Gastric Glands

Stomach mucosa composed of 3 layers - 1.) simple mucous-secreting columnar epithelium, 2.) a layer of loose connective tissue of lamina propria, and 3.) the smooth muscle of muscularis mucosa.

In the fundus and the body area of a stomach, the epithelium invaginates into the lamina propria layer, making up the "gastric glands." These glands empty into "gastric pits."

A gastric gland contains 4 types of cells:

1. Mucous neck cells

Mucous neck cells are low columnar mucous-secreting cells found in the neck of the gastric glands. They produce alkaline secretion to lubricate and protect stomach lining from highly acidic environment.

2. Chief Cells

Chief cells are prominently found in the gastric glands as pyramidal shape cells with pink zymogen granules. Their basal surface are basophillic from the presence of high RERs for protein synthesis. These granules contain pepsinogen, a precursor of gastric pepsin, and lipase. Pepsinogen are cleaved into its active form, pepsin, under low pH environment. Chief cells are found at the base of the gastric glands with a lifetime of a year.

3. Parietal cells

Parietal cells are large, polygonal shaped cells with centralized nuclei and highly acidophillic cytoplasm. These cells are found around the neck of the gastric glands and can be distinguished from other cells by the presence of intracellular calnaliculae. They produce and secret HCl, stomach acid, and intrinsic factor (IF). H+ is pumped into the lumen of the stomach via H+/K+ countertransporter and binds with Cl-. H+/K+ countertransporter is the target of H+-blocker medication used in gastric ulcer disease. On the other hand, IFs form complexes with Vitamin B12 and capture the vitamin for absorption in the ileum. Parietal cells are turned over once every year.

4. Enteroendocrine cells

Enteroendocrine cells are located at the base of gastric glands and secret their products into the vascular system. Their secretions regulate motility and secretions of other cells in the gastrointestinal tract. Entereoendocrine cell's products include histamine, serotonin, motilin, somatostatin, cholecystokinin (CKK), gastric inhibitory peptide (GIP), etc. An example of enteroendocrine cell type is enterochromaffin cells which produce and secrete histamine, a hormonal activator of HCl secretion.

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