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Nutrition and Digestion Chapter 38 Nutrition The process by which organisms get food and break it down for metabolism 6 Essential Nutrients Proteins (organic) Carbohydrates (organic) Fats (organic) Vitamins (organic) Minerals (inorganic) Water (inorganic) Remember… Autotrophsorganisms capable of making their own food Heterotrophsorganisms that must obtain food from their environment QuickTime™ and a Photo - JPEG decompressor are needed to see this picture. The Human Digestive System Also called the alimentary canal or the gastrointestinal tract Diagram of Human Digestive System 1. 2. 4. 5. 3. 6. 8. 7. 9. 10. 11. Digestive system organs The alimentary canal (digestive tract) of the human is made up of the following ordered sequence. Food passes through these structures: -oral cavity or mouth -pharynx -esophagus -stomach -small intestine -large intestine Accessory organs Other organs/glands are important for disgestion. Food does not pass through these structures: -gall bladder -liver -pancreas -appendix Functions of all organs and structures in the human digestive system I. Oral cavity or mouth 2. Lining of the mouth is epithelial tissue: 1. 3. 1. 2. 3. 4. Salty Sweet Sour Bitter Stimulation of taste buds results in secretion of saliva 4. Secretes mucous (protection) This starts chemical digestion Carbohydrate digestion begins in the mouth (amylase) Teeth begun mechanical digestion II. Pharynx Food passes through this narrow region and goes into the esophagus. III. Esophagus Tube that connects the pharynx to stomach. Food enters by “wavelike” motion of smooth muscle contractions called peristalsis. IV. Stomach sac like contains gastric juice This is water, hydrochloric acid, mucus, and the enzyme pepsin. Protein digestion begins here. Bacteria are destroyed by acid environment Peristalsis is occurring here. Ulcers may develop here. V. Small intestine About 20-25 feet long Contains folds or villi that increase the surface area Villi___________ Small intestine con’t Most absorption of nutrients into the blood stream occurs here. Most chemical digestion is occurring here. Lipid digestion occurs here. Peristalsis is continuing. The small intestine receives secretions from the liver and pancreas. VI. Large intestine (colon) Water absorption Feces formation Appendix located at end of large intestine This is a vestigial organ-it no longer has a useful function. VII. Liver Largest organ Functions: Secretes bile Produces urea Breakdown of worn out red blood cells Breakdown of proteins into amino acids Removes sugar from blood Stores sugar as glycogen Liver con’t Excessive use of alcohol and some drugs can cause damage to the liver Bile produced by liver is stored in gallbladder. Function is to break up lipids Therefore people without a gallbladder must watch their fat intake. VIII. Pancreas Functions Hormone secretion. (hormone-chemical in blood for regulation) Secretes enzymes into small intestine for digestion. Regulates blood sugar levels. Cells inside pancreas called the Islets of Langerhans… Secretes glucagon when blood sugar is too low Secretes insulin when blood sugar levels are too high QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Malfunctions of the Digestive Tract Ulcers-erosion of the lining in the stomach Constipation-large intestine emptied with difficulty. Caused by too much water absorption in large intestine Diarrhea-disturbance characterized by decreased water absorption and watery feces. May result in severe dehydration. Appendicitis-inflammation of appendix Gall stones-accumulation of cholesterol in gall bladder