Gastric Secretion And Digestion In The Stomach Notes
This is a sample of our (approximately) 4 page long Gastric Secretion And Digestion In The Stomach notes, which we sell as part of the Gastrointestinal (GI) System Notes collection, a 1st (70-80%) package written at Bristol University in 2012 that contains (approximately) 57 pages of notes across 19 different documents.
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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)
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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