Ch. 7.2 The Digestive System

1. Ch. 7.2 The Digestive System

2. 1. stages in food processing ingestion digestion absorption elimination - the process that breaks down food into small molecules so that they can be absorbed and moved into the blood 2. digestion

3. 3. mechanical digestion - takes place when food is chewed, mixed, and churned 4. chemical digestion - chemical reactions occur that break down large molecules of food into smaller ones

4. 5. What happens after digestion? • from blood, food molecules transported across cell membrane to be used by the cell • unused molecules leave your body as wastes 6. enzyme • a type of protein that speeds up the rate of a chemical reaction in your body • some reduce the amount of energy needed for a chemical reaction to begin

5. 7. enzymes in digestion • amylase- made in glands near mouth, help speed up breakdown of complex carbs • pepsin- in stomach, breaks down complex proteins • pancreas releases enzymes into small intestine- some break down starches, some break down fats, and some break down proteins

6. 8. organs of the digestive system - mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus - tongue, teeth, salivary glands, liver, gallbladder, and pancreas 9. accessory organs

7. mechanical digestion- chew your food • chemical digestion- food mixes with saliva • saliva- mostly water, also mucus and an enzyme that breaks down starch into sugar • food is moved by tongue to back of mouth, swallowed, and passes into esophagus 10. mouth

8. 11. esophagus • muscular tube about 25 cm long • takes 4 to 6 seconds for food to move through esophagus into stomach • mucous glands keep food moist, smooth muscle keeps food moving down by squeezing

9. - waves of muscle contractions that move food through the entire digestive tract 12. peristalsis

10. 13. stomach • a muscular bag with folds on the inside • mechanical digestion- food is mixed in stomach by peristalsis • chemical digestion- food mixed with enzymes and digestive solutions to break it down • acidic solution destroys bacteria in food • food moves through stomach in 2 to 4 hoursand is changed to chyme

11. 14. chyme • thin, watery liquid made from stomach breaking down food, moves from stomach to small intestine

12. small in diameter, 4 to 7 meters long • first part called duodenum- most digestion takes place here, bile from liver is added to food and breaks up fat particles • digestive solution from pancreas contains bicarbonate ions and enzymes- neutralize stomach acid • pancreas makes insulin which allows glucose to pass from bloodstream into cells • absorption takes place in folds and villi • nutrients move from villi into blood and to cells • undigested and unabsorbed food move into large intestine 15. small intestine

13. - fingerlike projections on folds in small intestine 16. villi 17. large intestine • main job is to absorb water from the undigested mass in chyme • chyme can stay here for up to 3 days • rest of undigested food becomes more solid and passes through rectum and out through the anus

14. bacteria is not always harmful • in large intestine feed on undigested material and make vitamins you need • breakdown of intestinal materials by bacteria produce gas 18. bacteria