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PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Tenth Edition Shier w Butler w Lewis Chapter 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Chapter 17 Digestive System Functions of Digestive System • ingestion • mechanical digestion • chemical digestion • propulsion • absorption • defecation 2 Major Organs 3 Alimentary Canal Wall 4 Movements of the Tube • mixing movements • peristalsis 5 Innervation of the Tube • submucosal plexus – controls secretions • myenteric plexus – controls gastrointestinal motility • parasympathetic impulses – increase activities of digestive system • sympathetic impulses – inhibit certain digestive actions 6 Palate • roof of oral cavity 7 Salivary Glands 8 Secretions of Salivary Glands • Parotid glands • clear • water, serous fluid • rich in amylase • Sublingual glands • primarily mucus • most viscous • Submandibular glands • primarily serous fluid • some mucus 9 Swallowing Mechanism • soft palate and uvula raise • hyoid bone and larynx elevate • epiglottis closes off top of trachea • longitudinal muscles of pharynx contract • inferior constrictor muscles relax and esophagus opens • peristaltic waves push food through pharynx 10 Swallowing Mechanism 11 Esophagus 12 Stomach 13 Lining of Stomach 14 Gastric Secretions • pepsinogen • from chief cells • inactive form of pepsin • pepsin • from pepsinogen in presence of HCl • protein splitting enzyme • hydrochloric acid • from parietal cells • needed to convert pepsinogen to pepsin • mucus • from goblet cells and mucous glands • protective to stomach wall • intrinsic factor • from parietal cells • required for vitamin B12 absorption 15 Phases of Gastric Secretion • Cephalic phase • triggered by smell, taste, sight, or thought of food • parasympathetic impulses trigger gastric juice secretion • Gastric phase • triggered by presence of food in stomach • gastrin released • gastric juice secreted • Intestinal phase • triggered by movement of food into small intestine • intestinal cells release intestinal gastrin • secretion of gastric juice 16 Regulation of Gastric Secretions 17 Gastric Absorption • some water • certain salts • certain lipid-soluble drugs • alcohol 18 Mixing and Emptying Actions 19 Enterogastric Reflex regulates the rate at which chyme leaves the stomach 20 Pancreas 21 Pancreatic Juice • pancreatic amylase – splits glycogen into disaccharides • pancreatic lipase – breaks down triglycerides • trypsin, chymotrypsin, and carboxypeptidase – digest proteins • nucleases – digest nucleic acids • bicarbonate ions – make pancreatic juice alkaline 22 Regulation of Pancreatic Secretions • acidic chyme stimulates release of secretin • secretin stimulate release of pancreatic juice 23 Liver 24 Hepatic Lobule 25 The Paths of Blood and Bile in Hepatic Lobule 26 Liver Functions • produces glycogen from glucose • breaks down glycogen into glucose • converts noncarbohydrates to glucose • oxidizes fatty acids • synthesizes lipoproteins, phospholipids, and cholesterol • converts carbohydrates and proteins into fats • deaminates amino acids • forms urea • synthesizes plasma proteins • converts some amino acids to other amino acids • stores glycogen, vitamins A,D, B12, iron, and blood • phagocytosis of worn out RBCs and foreign substances • removes toxins from blood • produces and secretes 27 Composition of Bile • water • bile salts • emulsification of fats • absorption of fatty acids, cholesterol, and fat-soluble vitamins • bile pigments • cholesterol • electrolytes 28 Gallbladder 29 Regulation of Bile Release • fatty chyme entering duodenum stimulate gallbladder to release bile 30 Three Parts of Small Intestine 31 Mesentery • suspends portions of the small intestine from the posterior abdominal wall 32 Intestinal Villus 33 Intestinal Epithelium 34 Wall of Small Intestine 35 Secretions of Small Intestine • peptidase – breaks down peptides into amino acids • sucrase, maltase, lactase – break down disaccharides into monosaccharides • lipase – breaks down fats into fatty acids and glycerol • enterokinase – converts trypsinogen to trypsin • somatostatin – hormone that inhibits acid secretion by stomach • cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile • secretin – stimulates pancreas to release bicarbonate ions in pancreatic juice 36 Regulation of Small Intestinal Secretions • mucus secretion stimulated by presence of chyme in small intestine • distension of intestinal wall activates nerve plexuses in wall of small intestine • parasympathetics trigger release of intestinal enzymes 37 Absorption in the Small Intestine • monosaccharides and amino acids • through facilitated diffusion and active transport • absorbed into blood • electrolytes and water • through diffusion, osmosis, and active transport • absorbed into blood 38 Absorption in the Small Intestine • fatty acids and glycerol • several steps • absorbed into lymph and blood 39 Movements of the Small Intestine • mixing movements • peristalsis – pushing movements • segmentation – ringlike contractions • overdistended wall triggers peristaltic rush resulting in diarrhea 40 Large Intestine 41 Large Intestinal Wall 42 Functions of Large Intestine • little or no digestive function • absorbs water and electrolytes • secretes mucus • houses intestinal flora • forms feces • carries out defecation 43 Movements of Large Intestine • slower and less frequent than those of small intestine • mixing movements • peristalsis • mass movements usually follow meals 44 Feces • water • electrolytes • mucus • bacteria • bile pigments altered by bacteria provide color • smell produced by bacterial compounds 45 Clinical Application Hepatitis • inflammation of the liver • most commonly caused by viral infection • can be caused by reactions to drug, alcoholism or autoimmunity Signs and Symptoms • headache • low fever • fatigue • vomiting • rash • foamy urine • pale feces • jaundice • pain Hepatitis A – not washing hands or eating raw shellfish Hepatitis B – chronic; serum Hepatitis C – serum Hepatitis D – very severe; only produces symptoms if infected with B; serum Hepatitis E, F, G – more rare 46