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Gastric Secretion And Digestion In The Stomach Notes

Medicine Notes > Gastrointestinal (GI) System Notes

This is an extract of our Gastric Secretion And Digestion In The Stomach document, which we sell as part of our Gastrointestinal (GI) System Notes collection written by the top tier of Bristol University students.

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Lecture 7 & 8 Gastric secretion and digestion in the stomach






Basic functions of stomach digestion o Reservoir- Gastric motility o Digest proteins- Pepsins o Essential for vit B12 absorption- Intrinsic factor (cells of the corpus) Gastric secretion o 1.5-2.5 litres per day; pH 0.9-1.5 o Composition: HCl, pepsins (pepsinogen first), intrinsic factor, mucus & HCO3(keeps lining of stomach intact in presence of acid) Gastric mucosa divided into 3 regions o CARDIAC GLANDULAR REGION
? Main function is mucus secretion
? Not very many acid secreting cells o OXYNIC GLANDULAR REGION
? Few gastrin & histamine producing cells (regulatory molecules)
? Secrete: HCl, intrinsic factor, pepsinogens, mucus, histamine o PYLORIC GLANDULAR REGION
? Secrete: Mucus, Gastrin, Somatostatin (last two= regulatory molecules)
? Won't see gland producing acid Structure of gastric mucosa o Gastric pits (G cells)= Gastrin o Surface epithelial cells= Mucus, HCO3o Mucus neck cells= Mucus o Parietal cell= HCl, Intrinsic factor o Chief cell= Pepsinogens o Endocrine cells= Histamine (ECL cell), Somatostatin (D cell) Secretion of HCl o Function of HCl
? Promote pepsin activation (from pepsinogen)
? Kill/inhibit microorganisms
? Stimulate secretions in small intestine
? Helps iron & calcium absorption in small intestine (WON'T BE TESTED) o Morphological changes that accompany HCl secretion
? Resting parietal cells

* Tubulovesicles (released into apical membrane, signal)

* Not a large surface area (no finger like projections)
? Active parietal cells

* Larger secretory membrane, more H+ pumps, K+ and Clchannels

* Increase in surface area (finger like projections)

* Total transport across membrane= Number transporters X Active o Cellular mechanisms of HCl secretion

1. H+/K+ ATPase uses energy to pump out H+ ions into lumen and K+ in

2. Apical membrane K+ channels recycle K+ ions across apical membrane

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