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DIGESTIVE SYSTEM 15.2 I. STEPS OF DIGESTION A. Ingestion (eat food) B. Digestion (break food down into small pieces that can be moved into the blood) C. Absorption (nutrients diffuse into bloodstream) D. Elimination (remove wastes) II. TYPES OF DIGESTION A. Mechanical- Food is mixed, chewed or churned B. Chemical- Chemical reactions occur that break down food into smaller pieces 1. Enzymes- special proteins that break down food III. DIGESTIVE ORGANS A. Mouth 1. Mech: Teeth chew, tongue moves food, swallow 2. Chem: Saliva contains an enzyme called amylase that breaks down starches into simple sugars III. DIGESTIVE ORGANS B. Esophagus 1. Epiglottis covers the trachea when swallowing. 2. Peristalsis- Involuntary muscle contractions that move food down the esophagus III. DIGESTIVE ORGANS C. Stomach 1. Mech: Food is mixed by stomach contractions (peristalsis) 2. Chem: Food is mixed with an enzyme called pepsin to break down proteins III. DIGESTIVE ORGANS a. HCl activates the pepsin b.Stomach is protected from the acid by mucus 3. The food is turned into chyme in 2-4 hours. III. DIGESTIVE ORGANS D. Small (diameter) Intestine 1. Duodenum- First section of the S.I. where most digestion takes place a. Fats are broken down by a green fluid called bile b. Enzymes from the pancrease break down carbs, protein and fats III. DIGESTIVE ORGANS 2. Absorption of nutrients takes place in the rest of the S.I. a. Villi- Fingerlike projections of the S.I. that increase surface area and enhance absorption. b. Towel demonstration III. DIGESTIVE ORGANS c. Nutrients are absorbed in the S.I. and enter the bloodstream so they can be used by cells. III. DIGESTIVE ORGANS E. Large (diameter) Intestine 1. Any remaining chyme enters the L.I. where water is absorbed back into the body a. Feces is formed and stored in the rectum III. DIGESTIVE ORGANS 2. The feces is excreted through the anus. a. Feces may be stored for up to 3 days! The entire digestion process takes 24-35 hours! IV. ACCESSORY ORGANS A. Liver- Secretes bile into the S.I. to break down fats 1. Bile is stored in the gallbladder until needed. IV. ACCESSORY ORGANS B. Pancreas- Secretes enzymes into S.I. to breakdown fats, carbs and proteins. 1. Also makes insulin that helps glucose (sugar) pass from the bloodstream into cells. V. BACTERIA A. Not all bacteria are bad! 1. They make vitamins in the L.I. 2. They break down undigested compounds a. Gas is a by product! 1. 2. 3. 4. RECAP What are the 4 steps in the digestive process? What are the main digestive organs? What are the accessory organs? Why are enzymes important?