Digestion In The Intestine Notes
This is a sample of our (approximately) 4 page long Digestion In The Intestine 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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Digestion In The Intestine Revision
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Lecture 9 Digestion in the intestine
Secretions in the intestine o Duodenum
1 litre per day, pH 7.6
Composition: mucus, water enterokinase, water etc. o Liver
0.5 litres per day, pH 7.4
Composition: bile acids, cholesterol, phospholipids etc. o Pancreas
1~2 litres per day, pH 7.8-8.4 (very alkaline, secretes lots of HCO3-)
Composition: salts and enzymes (enteropeptidase) Secretions of the pancreas o Endocrine- insulin and glucagon o Exocrine- salts and water, enzymes o Functions of pancreatic juices
Salts and water (HCO3-, NaCl, Water)= make right environment for enzymes
Enzymes (proteases, lipases, a-amylases)= digest major classes of foodstuffs o Structure of the pancreas
Like a bunch of grapes
Main collecting duct= large stalk; Interlobular duct= small stalk; Acinar=
Acinar cells fall of zymogen granules for secretory purposes o Movement of newly synthesised proteins through secretory pathway (in Acinar cell)
Rough ER-->Golgi-->Condensing vacuoles-->Zymogen granules
5-15g of protein each & every day o Secretion of enzymes
Key stimulators: CCK & Secretin (lesser role but does give rise to cAMP)
Cause the release of vesicles by exocytosis
CCK acts on receptor on basolateral membrane giving rise to IP3 and DAG in cell that leads to exocytosis of materials into lumen (enteric NS acting on M3 receptors has same effect)
Secretin receptors activated to give rise to cAMP, Somatostatin inhibits this
Things released into lumen:
• Proteases (Trypsin, chymotrypsin, carboxypeptidases)= as Zymogens
• Lipases & a-amylases= as enzymes o Composition of pancreatic juice made by both Acinar & duct lining epithelial cells
• "Leaky" epithelium
• Active/inactive enzymes & Cl1 secreted transcellularly
• Na+ and H20 secreted paracellularly
Duct-lining epithelial cells
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