Digestive System

Digestive System - THE DIGESTIVE SYSTEM ASSIGNED READING:...

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THE DIGESTIVE SYSTEM ASSIGNED READING: PAGES 966-969; 973-1005 IN SALADIN 5TH EDITION
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DIGESTIVE FUNCTION Stages of digestion: Ingestion: intake of food Digestion: mechanical and chemical breakdown of food Absorption: uptake of macro- molecules into the epithelial cells of the digestive tract and then into the blood or lymph Compaction: absorbing water and consolidating indigestibles into feces Defecation: elimination of feces
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GENERAL ANATOMY Digestive tract (aka: alimentary canal, GI tract) Accessory organs Structures not part of the canal (teeth, tongue, salivary glands, liver, gallbladder, and pancreas)
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GENERAL ANATOMY The peritoneum Within the abdominal cavity Contains most of the GI tract Serosa define the cavity’s boundaries Parietal peritoneum Visceral peritoneum Peritoneum (peritoneal cavity) Mesenteries
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GENERAL ANATOMY OF THE DIGESTIVE TRACT Mucosa : •inner epithelium lamina propria •muscularis mucosa mucosa-associated lymphatic tissue (MALT) Submucosa : connective tissue containing capillaries, lymph vessels Muscularis externa : •Inner circular layer Outer longitudinal layers Serosa : visceral peritoneum, secretes serous fluid Layers of the digestive tract: Submucosal plexus: controls glandular secretion of mucosa controls movements of muscularis mucosae Myenteric plexus: controls peristalsis and other contractions of muscularis externa lumen diaphragm The enteric nervous system:
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REGULATION OF GI TRACT How does the GI tract decide to change its activity? Stimuli are… Mechanical Chemical Responses are mediated by… Long (vagovagal) reflexes Short (myenteric) reflexes Hormones Effects are… Secretion Motility
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SALIVA AND THE SALIVARY GLANDS Saliva, what’s it good for? moistens mouth: mucus starch ( amylase ) and fat ( lipase ) digestion cleanse teeth: HCO 3 - inhibits bacterial growth: lysozyme, IgA dissolves molecules so they can stimulate the taste buds moistens food and bind it together into bolus to aid in swallowing
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SALIVA AND THE SALIVARY GLANDS intrinsic salivary glands – dispersed amid oral mucosa all secrete saliva at a fairly constant rate extrinsic salivary glands – three pair connected to oral cavity by ducts Parotid, submandibular, and sublingual glands Secrete primarily when eating
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CONTROL OF SALIVARY GLANDS Mucous cells Serous cells Salivary duct mucous cells secrete mucus stimulated by sympathetic NS serous cells secrete thin fluid rich in amylase and electrolytes Stimulated by parasympathetic NS
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Pharynx: muscular tube extending from nasal cavity, to oral cavity, to esophagus Swallowing ( deglutition ) begins here
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This note was uploaded on 11/04/2011 for the course BIOL 252 taught by Professor Johnson during the Fall '07 term at UNC.

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Digestive System - THE DIGESTIVE SYSTEM ASSIGNED READING:...

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