Digestion - BMED 3100 Systems Physiology Gastrointestinal...

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BMED 3100 Systems Physiology Gastrointestinal (GI) System
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2 Gastrointestinal (GI) System - Anatomy GI Tract Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Accessory Organs Salivary Glands Liver Gallbladder Pancreas
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3 Processes of GI Tract Digestion, Secretion, Absorption, Motility
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4 GI System - Anatomy Mouth: chewing - starts digestion Salivary glands : secrete saliva – Moisten and lubricate food – Digest polysaccharides by amylase – Dissolve food – Antibacterial actions Pharynx & Esophagus : pathway to stomach •S t o m a c h : store, dissolve, partially digest macromolecules; regulate emptying of chyme (proteins, complex sugars, fat, salt, water) into small intestine Small intestine – guarded by the pyloric valve to control amount of chyme entering, digestion completed in small intestine, absorption – duodenum: first 25 cm – jejunum: middle section – ileum: last section (jejunum and ileum together are 260cm) – Most digestion/absorption in duodenum and jejunum Intestinal enzymes secreted by accessory glands: pancreas, liver Large intestine : converts watery chyme to feces
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6 Digestive secretions from the liver and the pancreas delivered to the duodenum (small intestine) via the sphincter of Oddi.
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8 ANATOMY OF THE GI TRACT WALL
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9 ANATOMY OF THE GI TRACT WALL
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10 Villi and Microvilli increase surface area for absorption nutrients ANATOMY OF THE GI TRACT WALL
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11 Luminal Stimuli 1. Distension of the wall (mechanical) 2. Chyme osmolarity (total solute concentration) 3. Chyme acidity 4. Chyme composition (concentrations of digestion products) Effectors 1. Muscle layers 2. Exocrine glands GI Reflexes
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12 Neural Regulation Enteric nervous system - coordinates digestion, secretion, and motility to optimize nutrient absorption. Activity modified by information from the CNS and from local chemical and mechanical sensors.
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14 Neural Regulation
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15 Hormonal Regulation Gastrin CCK Secretin GIP Peptides/Amino Acids Fatty Acids Oral Glucose Acid Distension Parasympathetic Nerves S = Stimulates ; I = Inhibits SS S S S S S S I
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16 Hormonal Regulation Gastrin CCK Secretin GIP ACTION Acid Secretion Pancreatic HCO 3 Pancreatic Enzymes Bile HCO 3 Gallbladder Contraction Gastric Emptying Insulin Release GI Mucosal Growth Pancreatic & GB Growth Intestinal Motility S = Stimulates ; I = Inhibits; P = Potentiates SI I PS S S S S S I P S S S
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18 Phases of Control Cephalic Phase – Receptors are stimulated by sight, smell, taste, and chewing – Mediated by parasympathetic division via vagus nerve Gastric Phase – Stimuli in stomach: distension, acidity, amino acids, and peptides
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Digestion - BMED 3100 Systems Physiology Gastrointestinal...

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