Notes

Exocrine Cells of Stomach

Located in tubular gastric glands that comprise gastric pits
– Epithelial cells at entrance of gastric pits: secrete thick mucus
– Mucous layer
– Submucosa layer
Secrete products into stomach lumen
Secretions convert food to chyme

Mucous cells (mucous neck cells): secrete alkaline, bicarbonate mucus, which protects our stomach wall from erosion in an acidic luminal environment.
Chief cells: secrete pepsinogen, an inactive enzyme that, once activated, breaks down proteins.
Pepsinogen is a zymogen
– An inactive enzyme that, once activated, breaks down proteins.
– A substance must convert to its active form, pepsin
Pepsin
– Breaks down peptide bonds to promote chemical breakdown.
Parietal cells
– Secrete HCl which denature proteins.
HCl functions:
– Converts pepsinogen → its active form: pepsin.
– Aids in the breakdown of food → smaller particles.
– Denatures proteins via its acidic environment.
– Kills most of the microorganisms that we ingest with our food, thus, providing a protective function. (Tight junctions between the digestive tract epithelium and mucus production serve as a protective barrier).
– Facilitates chemical breakdown; it denatures proteins but, unlike pepsin, it doesn't break peptide bonds.

Rapidly divide and mature into cells that produce gastric mucosa
– Replenishes gastric mucosal cells every 3 days due to constant exposure to the harsh, acidic environment in the stomach.