1. I. Nutrients
A. Organic
1. carbohydrates (4.1 calories/gram)
2. proteins (4.1 cals/g)
- 8 essential amino acids
3. fats (9.3 cals/g)
4. fiber

2. B. Vitamins

3. C. Minerals

4. II. Digestive System
A. Structures

5. B. Layers
1. epithelial lining
2. muscular wall
3. external covering

6. C. Chewing/Initial Digestion
1. teeth
a. herbivores
- flat teeth for grinding
- longer intestines
b. carnivores
- pointed teeth for tearing
c. omnivores
- both pointed and flat teeth

7. 2. crop
a. softening
b. storage
- for regurgitation
- to avoid predators
c. milk (males or females)

8. 3. gizzard
- grinding and churning
- some storage

9. 4. saliva
- moisture
- mucus
- enzymes (amylase, lysozyme)

10. D. Swallowing
- epiglottis

11. E. Esophagus
1. peristalsis
2. sphincter
- true in rodents, cattle, and horses
- rats and mice cannot vomit (rare in horses)

12. F. Stomach
1. expansive
2. churning action
3. gastric juice
a. parietal cells (HCl)
b. chief cells (pepsinogen  pepsin)

13. 4. protein digestion
5. chyme
6. little absorption

14. 7. ulcers
- excessive acid
- Helicobacter pylori
80% of gastric ulcers
Robin Warren and Barry Marshall (Nobel 2005)
Marshall proved by infecting himself

15. G. Small intestine (about 6 meters in humans)

16. G. Small intestine (about 6 meters in humans)
1. duodenum
a. is the initial segment (about 25 cm)
b. focal point of digestion
- chyme from stomach
- digestive enzymes from pancreas
- bile from liver and gallbladder

17. 2. jejunum/ileum
a. villi
b. microvilli
c. huge increase in surface area for absorption
- about 300m2 in humans

18. H. Cecum
1. pouch at beginning of colon

19. 2. prominent in some herbivores
- contains cellulose-digesting bacteria or protists
- some of the nutrients absorbed by cecum and colon

20. I. Colon
1. no villi or folds
2. no digestion (except for cecum in herbivores)

21. 3. absorption
a. water
b. ions
c. vitamins
- biotin
- folic acid
- K
- K from normal flora in mammalian colon

22. 4. feces
- 30% of dry weight is bacteria
5. rectum
6. anus

23. J. Ruminants (cattle, sheep, deer)
- 4 chambered stomach
1. bacteria or protozoa in rumen and reticulum
2. regurgitation (rumination)
3. enzymatic digestion begins in abomasum
- some of the microbes are also digested

24. K. Coprophagy
1. rodents and lagomorphs (rabbits and hares)
2. because cecum is critical for cellulose digestion