1. I. Digestive System

2. A. Digestive tract 1. Mouth-->Esophagus-->Stomach-- >Small Intestine-->Large Intestine-- >Anus 2. The liver and pancreas aid in digestion but are not part of the digestive tract.

3. 3. Mechanical & Chemical Digestion a. Mechanical Digestion -takes place when food is chewed (mouth), churned in stomach, and acted on by bile. b. Chemical Digestion - breaks down large molecules of food into smaller molecules. (mouth, stomach, & small intestine)

4. 4. Enzymes and water work together to digest food a. specific enzymes digest specific nutrients

5. B. Structures and Functions in the digestive system 1. Mouth a. chewing - grinds food into tiny pieces (mechanical) small pieces have more surface area than one large hunk.

6. b. tongue and teeth mix food with saliva (chemical) 1) Saliva adds water, mucus, and enzymes to food. 2) Mucus - makes it so food moves smoothly through the digestive tract. 3) Enzyme - amylase - added to food in the mouth. - amylase changes starches into sugar

7. 2. Esophagus - "food tube" a. 30 cm long (1 foot) b. connects mouth to the stomach c. Muscles in digestive tract push food through muscles contract (behind food) muscles relax and push and widen(in front of food) these waves or contractions are called peristalsis (happen all through the digestive tract).

8. 3. Stomach(takes about 4 hours) a. organ containing muscular walls which contract to mix food(mechanical) with acid and enzymes (chemical).

9. b. Gastric glands produce gastric juices - weak hydrochloric acid and pepsin (digest protein) c. chyme - thin watery liquid which food has been changed into.

10. d. common stomach problems 1) Heartburn - if some of the stomach acid gets up into the esophagus 2) Ulcer - acid digests the stomach wall - secretions of mucus help protect stomach walls

11. 4. Small Intestine a. coiled tube - 7m long and 2.5cm in diameter b. most of our food is digested in the small intestine. duodenum - first part of the small intestine

12. c. Digestive Juices 1) Intestinal Juice a) produced by glands in the wall of the small intestine b) contains enzymes which digest carbohydrates, fats, and proteins c) glands also produce large amounts of mucus to protect the intestinal wall

13. 2) Pancreatic Juice a) formed in pancreas - not part of the digestive tract b) contains enzymes which digest carbo, fat, and protein to produce glucose, fatty acids, glycerin, and amino acids. c) contains substances to neutralize acid which is mixed with food coming from the stomach.

14. 3) Bile - produced in the liver and stored in the gall bladder a) Gall Bladder - green colored bag attached to the liver. b) bile does not contain enzymes c) bile breaks fats down into tiny particles - increasing surface area and speeding up digestion

15. d. Food diffuses into the blood through the wall of the small intestine. 1) Villi - small fingerlike projections which increase the surface area of the small intestine. a) give a velvety appearance - "shag carpet"

16. b) contain blood and lymph –blood carries - amino acids, some vitamins, minerals –lymph carries - fatty acids, glycerin, & some vitamins

17. 2) Blood and lymph carry food nutrients to all parts of the body

18. 5. Large Intestine(Colon) a. Removes excess water from undigested food b. secretes mucus - to smooth passage

19. c. bacteria feed on undigested material (cellulose) and produce vitamins that the body needs. (symbiosis) d. Diarrhea - not enough water is removed by the large intestine.

20. 6. Rectum & Anus - have muscles which control the release of solid wastes (feces).