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Human Digestive System Digestive System Functions • • • • • Ingest food Break down food Move food through digestive tract Absorb digested food and water Eliminates waste materials Mouth Diagram of Teeth Mouth • • • • • • Breaks down food into small pieces Begins starch digestion (amylase) Saliva produces amylase and lubricates food Moves food into esophagus Epiglottis covers trachea Peristalsis moves food to stomach Esophagus • Pushes food to Stomach Motility: Peristalsis Peristalsis Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Figure 14.3B Slide 14.5 Stomach • • • • • Muscles churn food – mechanical digestion. Glands produce gastric juice = pepsin + HCl Pepsin breaks down proteins (only at pH 2) Food leaves after 2-4 hrs Pushes food through pyloric sphincter to small intestine Stomach Stomachh Small Intestine • Digestion is finished here – Peristalsis finishes mechanical digestion – Pancreatic juice produces enzymes to finish chemical digestion of fats, proteins and carbohydrates Small Intestine Small Intestine Digestive System Pancreas • Makes enzymes to break down fats, carbohydrates and proteins Liver • Produces bile • Processes food for use by body Question: What is the function of bile? Bile is stored in the gallbladder. Liver • Location – R. Hypochondrium – Epigastric region • 4 Lobes – – – – Left Quadrate Caudate Right • Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein 19 Liver • Functions – Makes bile • Detergent – emulsifies fats • Release promoted by: – Vagus n. – CCK – Secretin • Contains – – – – – – Water Bile salts Bile pigments Electrolytes Cholesterol Lecithin 20 Liver – Detoxifies/removes • Drugs • Alcohol – Stores • • • • – – – – Gycolgen Vitamins (A, D, E, K) Fe and other minerals Cholesterol Activates vitamin D Fetal RBC production Phagocytosis Metabolizes absorbed food molecules • Carbohydrates • Proteins • Lipids 21 Liver • Dual blood supply – Hepatic portal vein • Direct input from small intestine – Hepatic artery/vein • Direct links to heart 22 Liver Large Intestine • • • • Absorbs water Bacteria live here (produce methane) Bacteria produce B vitamins and Vitamin K Stores solid waste in rectum until elimination. Large Intestine Digestive Endocrine Glands • • • • Pancreas – insulin = blood sugar Thyroid – thyroxine = metabolic rates Thyroid – calcitonin = blood calcium levels Parathyroid – PTH = calcium, phosphorus absorption rates and helps make Vitamin D
