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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 4 Alimentary Canal Wall 5 Structure of the Wall • Serosa- made of visceral peritoneum, moistens, protects and lubricates • Muscular- smooth circular fibers-decreases diameter-smooth longitudinal-shortens tube • Sumucosa- nerves, blood vessels, loose c.t., transports absorbed nutrients and nourishes • Mucosa- epithelial, some c.t., some muscle secretes mucus, absorb, protect 6 Movements of the Tube • mixing movements • peristalsis 7 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 8 Mouth • ingestion • mechanical digestion • prepares food for chemical digestion 9 Tongue 10 11 Palate • roof of oral cavity 12 Primary Teeth • 8 incisors • 4 cuspids • 8 molars 13 Secondary Teeth 14 Section of a Tooth 15 Salivary Glands 16 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 17 Chemical Digestion in Mouth Saliva • 1-1.5 L per day • Mostly water as a solvent so food can be tasted • Mucin-causes food to stick together has lysozyme to kill bacteria • Amylase-breaks down starch • Neutralizes mouth acids-6.8, cleans mouth 18 Pharynx 19 Pharynx • Connects nasal and oral cavities with larynx and esophagus, lined with mucous mem., muscles constrict • Nasopharynx- above soft palate has pharyngeal tonsils on walls, behind nose, passageway for air • Oropharynx- below soft palate above epiglottis, palatine tonsils on walls, food/air • Laryngopharynx- from epiglottis 20 downward to the esophagus Swallowing Mechanism • soft palate and uvula raise-nasal air passage shut off • hyoid bone and larynx elevate, epiglottis closes off trachea • tongue pushes against soft palate • longitudinal muscles of pharynx contract pulling pharynx up • inferior constrictor muscles relax and esophagus opens • peristaltic waves push food through pharynx to the esophagus, to the cardiac sphincter of the stomach 21 Swallowing Mechanism 22 Esophagus 23 Stomach 24 Radiograph of Stomach 25 Lining of Stomach 26 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 27 Phases of Gastric Secretion • Cephalic phase • triggered by smell, taste, sight, or thought of food • parasympathetic impulses trigger gastric juice secretion-gastrin • 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 28 Regulation of Gastric Secretions 29 Gastric Absorption • some water • certain salts • certain lipid-soluble drugs • alcohol 30 Mixing and Emptying Actions 31 Enterogastric Reflex regulates the rate at which chyme leaves the stomach 32 Pancreas 33 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 34 Regulation of Pancreatic Secretions • acidic chyme stimulates release of secretin • secretin stimulate release of pancreatic juice 35 Liver 36 Hepatic Lobule 37 The Paths of Blood and Bile in Hepatic Lobule 38 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 • 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 bile 39 Composition of Bile • water • bile salts • emulsification of fats • absorption of fatty acids, cholesterol, and fat-soluble vitamins • bile pigments • cholesterol • electrolytes 40 Gallbladder 41 Regulation of Bile Release • fatty chyme entering duodenum stimulate gallbladder to release bile 42 Three Parts of Small Intestine 43 Mesentery • suspends portions of the small intestine from the posterior abdominal wall 44 Intestinal Villus 45 Intestinal Epithelium 46 Wall of Small Intestine 47 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 48 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 49 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 50 Absorption in the Small Intestine • fatty acids and glycerol • several steps • absorbed into lymph and blood 51 Movements of the Small Intestine • mixing movements • peristalsis – pushing movements • segmentation – ringlike contractions • overdistended wall triggers peristaltic rush resulting in diarrhea 52 Large Intestine 53 Large Intestinal Wall 54 Functions of Large Intestine • little or no digestive function • absorbs water and electrolytes • secretes mucus • houses intestinal flora • forms feces • carries out defecation 55 Movements of Large Intestine • slower and less frequent than those of small intestine • mixing movements • peristalsis • mass movements usually follow meals 56 Feces • water • electrolytes • mucus • bacteria • bile pigments altered by bacteria provide color • smell produced by bacterial compounds 57 Life-Span Changes • teeth become sensitive • gums recede • teeth may loosen or fall out • heartburn more frequent • constipation more frequent • nutrient absorption decreases • accessory organs age but the effects are less noticeable 58 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 59