1. Feeding and Digestion – Part 2 Biology 155 Spring 2010 B. L. Krilowicz

2. IV. Example of a Generalized Complete Digestive Tract: A. Mouth = specialized for food ingestion B. Oral cavityB. 2. Salivary glands C. esophagus D. Stomach or crop and gizzard E. 2. liver E. 2. Gall bladder E. 2. pancreas E. Small intestine F. Large intestine Anus Fig. 21.4

3. B. Oral Cavity – 1. starts mechanical breakdown of food with chewing, uses teeth and tongue a. makes swallowing easier b. increases surface area for enzyme action 2. starts chemical breakdown of carbohydrates salivary amylase carbohydrates smaller carbohydrates 3. saliva moistens food bolus to ease swallowing 4. taste buds – a. stimulate salivation, b. used in food rejection reflex Tongue with taste buds teeth duct from salivary gland Fig. 21.5

4. esophagus tongue Oral cavity C. Esophagus = muscular tube that transports food between oral cavity and the stomach or crop; carries bolus through the thoracic cavity Fig. 21.6

5. D. Stomach or a Crop and a Gizzard 1. Stomachs and crops – serve as storage organs, they are designed to release food to the small intestine at the appropriate rate for processing 2. Stomachs and gizzards – function in mechanical breakdown of food, stomachs make use of muscular movements, while gizzards use grinding

6. D. Stomachs (con’t) – 3. Start chemical breakdown of proteins pepsin Proteins smaller proteins HCl 4. HCl sterilizes food bolus Fig. 21.8

7. E. Small Intestine 1.Continues mechanical breakdown through muscular movements 2.Performs most chemical breakdown- a.Lumen – 1.Pancreatic fluids are released into the small intestine from the exocrine pancreas; includes bicarbonate, to neutralize stomach acid, and enzymes 2.Bile is produced in the liver and is stored in the gall bladder for release into the small intestine; fat emulsifier required for the chemical digestion of fats

8. Reactions of the Small Intestine Lumen small carbohydrates pancreatic amylase Small proteins proteases Fats and oilsfree fatty acids + monoglyceride lipases bile glucose Chemical bond Amino acid Amino Acid Amino acid Fig. 21.2B

9. The products of amylase and protease activity cannot be absorbed! Only the breakdown products of lipase action can be absorbed across the wall of the small intestine

10. b. Intestinal epithelium has the enzymes required to break the final bonds in dimers and trimers and absorb the monomers at the same time Fig. 21.10B

11. Large intestine anus F. Large Intestine – 1.Water and vitamin absorption 2.Defecation reflex allows elimination of non-digestible material through the anus Fig. 21.12