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Chapter 17 Digestive System Functions of Digestive System • • mechanical digestion • chemical digestion • • absorption • 17-2 Major Organs 17-3 Alimentary Canal 17-4 Alimentary Canal Wall 17-5 Movements of the Tube • mixing movements • 17-6 Mouth • ingestion • • prepares food for chemical digestion 17-8 Palate • roof of oral cavity 17-10 Primary Teeth • 8 incisors • 4 cuspids • 8 molars cross of tooth.mov Teeth and Plague.mov 17-11 Salivary Glands 17-14 Swallowing Mechanism 17-18 Esophagus 17-19 Stomach 17-20 Lining of Stomach Endoscopy of Stomach.mov Stomach.mov 17-22 Gastric Secretions • pepsinogen • inactive form of pepsin • • protective to stomach wall • • from pepsinogen in presence of HCl • protein splitting enzyme • intrinsic facto • required for vitamin B12 absorption • • from parietal cells • needed to convert pepsinogen to pepsin 17-23 Phases of Gastric Secretion • Cephalic phase • • parasympathetic impulses trigger gastric juice secretion • Gastric phase • • gastrin released • gastric juice secreted • Intestinal phase • • intestinal cells release intestinal gastrin • secretion of gastric juice 17-24 Gastric Absorption • some water • certain salts • certain lipid-soluble drugs • alcohol 17-26 Mixing and Emptying Actions 17-27 Pancreas 17-29 Pancreatic Juice • pancreatic amylase – • pancreatic lipase – breaks down triglycerides • trypsin, chymotrypsin, and carboxypeptidase – • nucleases – • bicarbonate ions – make pancreatic juice alkaline 17-30 Liver 17-32 Liver Functions •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 •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 17-35 Gallbladder gall stones.mov 17-37 Three Parts of Small Intestine 17-39 Intestinal Villus 17-41 Intestinal Epithelium 17-42 Wall of Small Intestine 17-43 Secretions of Small Intestine • peptidase – • sucrase, maltase, lactase – • lipase – • 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 17-44 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 17-46 Movements of the Small Intestine • mixing movements • peristalsis – • segmentation – ringlike contractions • overdistended wall triggers peristaltic rush resulting in diarrhea Small intestine.mov 17-48 Large Intestine 17-49 Large Intestinal Wall 17-50 Functions of Large Intestine • • • secretes mucus •forms feces • carries out defecation 17-51 Movements of Large Intestine • slower and less frequent than those of small intestine • mixing movements • peristalsis • mass movements usually follow meals 17-52 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 17-54 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 17-55