PGY300lec6GI copy

PGY300lec6GI copy - Small Intestine Silverthorn pages...

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Small Intestine Silverthorn pages 704-707 Dr John A. Krasney
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villus crypt Absorption Secretion
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Small Intestine Duodenum Jejunum Ileum 3 m in length (~9 feet). Very large surface area (300 m 2 ) due to plicae, crypts, villi and microvilli.
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Functions of Small Intestine Final digestion and absorption of nutrients is the exclusive function of the small intestine in mammals. Secretion of fluid (crypt cells). Absorption of fluid and nutrients (enterocytes located on villi).
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Intestinal Absorption of Water and Electrolytes The small intestine absorbs net amounts of water (7.5 L/day), Na + , Cl - and K + . The absorption of water and electrolytes follows osmotically the primary active transport of Na + and the secondary active transport of nutrients (monosaccharides, amino acids, peptides). Solvent Drag. • Small intestine also secretes NaCl, NaHCO 3 and water from Crypt cells.
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Intestinal Crypt Cell Secretion (One L/Day) Crypt Cell Lumen
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Crypt Cell Secretion Similar to pancreatic duct cell; Cl- enters cell via basolateral Na + - K + -2Cl - co-transporter. Secretagogues are Ach, Serotonin, histamine, bacterial enterotoxins, laxatives. Secretagogues activate CFTR channel (via ATP).
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CFTR channels are stimulated by v.choleri increasing ATP in Cholera leading to massive Cl - secretion, diarrhea and death due to dehydration. CFTR channels are defective in Cystic
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This note was uploaded on 01/10/2010 for the course PGY 300 taught by Professor Krasney during the Fall '05 term at SUNY Buffalo.

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PGY300lec6GI copy - Small Intestine Silverthorn pages...

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