Animal Nutrition II (Ch. 41)

1. Animal Nutrition II (Ch. 41) Guest lecturer: Letitia Reichart (Letty)

2. Roles of mouth, stomach, sm.&lg. Intestine in digestion Pepsin, pepsinogen Villi, microvilli Cecum Cellulose Cellulase Acid chyme Enzymatic hydrolysis Peristalsis Keywords

3. Mammalian Digestive System • Alimentary canal • Accessory glands • Salivary glands, pancreas, liver, gallbladder • Food moved by peristalsis

4. Mouth (oral cavity) • Mechanical • Teeth • Saliva • Enzymatic • Salivary amylase – breakdown of starch and glycogen

5. Throat (pharynx) & Esophagus • Throat – junction to esophagus & trachea • Epiglottis • Esophagus – uses peristalsis to move food to stomach

6. Contracted muscles Relaxed muscles Stomach Stomach • Stores food • Secretes gastric juices • Acid chyme

7. Cardiac orifice Esophagus Pyloric sphincter Liver Stomach Gall- bladder Pancreas Digestive mechanisms in stomach • Mechanical • Chemical • Enzymatic

8. Cardiac orifice Esophagus Pyloric sphincter Stomach Mechanical • Mixing and churning • Smooth muscle • Every 20 seconds

9. Chemical • Hydrochloric acid (HCl) • pH around 2 • Also breaks food down

10. Enzymatic • Pepsin • Breaks down proteins

11. Why doesn’t pepsin digest stomach? Gastricpit Interior surface of stomach Gastric gland Mucus cells Chief cells Parietal cells

12. Activation of pepsin Pepsinogen Pepsin (active enzyme) HCl Chief cell Parietal cell

13. Cardiac orifice Pyloric sphincter Stomach Stomach • After mechanical and enzymatic digestion: -Acid chyme (nutrient-rich broth) - Pyloric sphincter to the small intestine

14. Small intestine • Most of: • Enzymatic digestion occurs here • Absorption of nutrients into the blood stream occurs here Small intestine

15. Protein digestion Nucleic acid digestion Fat digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides Disaccharides Salivary amylase Smaller polysac- charides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine DNA, RNA Fat globules Polysaccharides Polypeptides Pancreatic amylases Pancreatic nucleases Pancreatic trypsin and chymotrypsin Bile salts Maltose and other disaccharides Fat droplets Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Epithelium of small intestine (brush border) Small peptides Nucleotidases Nucleosides Dipeptidases, carboxy- peptidase, and aminopeptidase Disaccharidases Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Amino acids Monosaccharides Figure 41.21 p. 859 in Campbell

16. Figure 41.19 p. 858 in Campbell Bile Liver Gall- bladder Stomach Acid chyme Intestinal juice Pancreatic juice Pancreas Duodenum of small intestine

17. Pancreas • Secretes proteases into duodenum

18. Membrane-bound enteropeptidase Fig. 37.13 Inactive trypsinogen Trypsin Other inactive proteases Active proteases Active proteases Lumen of duodenum Why doesn’t the small intestine digest itself? Pancreas

19. Liver • Produces bile that is stored in gallbladder • Bile contain bile salts • Bile salts aids digestion and absorption of fats

20. Vein carrying blood to hepatic portal vessel Muscle layers Large circular folds Villi Intestinal wall Most nutrient absorption occurs in small intestine

21. Blood capillaries Epithelial cells Lacteal Lymph vessel Villi Structure of small intestine

22. Microvilli (brush border) Epithelial cells Microvilli • Aid in nutrient transport across epithelial cells of sm. intestine into bloodstream

23. Ascending portion of large intestine Ileum of small intestine Large Intestine Rectum Anus Appendix Cecum Large intestine (colon) • Major function is to reabsorb water

24. Here are a few review questions

25. What would happen if you had a defect in pepsin production?

26. What would happen if you had a defect in pepsin production? • A. carbohydrate would not be digested well • B. meat would not be digested at all • C. perhaps decreased absorption of protein

27. What would happen if you had a defect in salivary amylase production?

28. What would happen if you had a defect in salivary amylase production? • A. You would die • B. You would be unable to digest starch • C. The pH of the stomach would be affected • D. None of the above

29. Which of the following would you least like to donate to science while you are still alive? • A. Cecum • B. Pancreas • C. Reproductive organs

30. What would happen if you had a defect in small intestine enteropeptidase?

31. What would happen if you had a defect in small intestine enteropeptidase? • A. Pancreatic enzymes would not be activated • B. Liver enzymes would increased • C. Your small intestine would become blocked • D. None of the above

32. Variations of vertebrate digestive system • Herbivorous mammals • Specialized fermentation chambers

33. Small intestine Stomach Small intestine Cecum Colon (large intestine) Herbivore Carnivore Coyote vs. Koala

34. Why does herbivory require specializations? • Plant tissue • Harder to break up • Contains cellulose • Nutrients less concentrated than meat

35. Structure of cellulose

36. Only bacteria and protozoa can break down cellulose Via the enzyme cellulase

37. Small intestine Stomach Cecum Colon (large intestine) Herbivore Cecum • Pouch at junction between lg and sm intestine • Large cecum in rabbits, some rodents, koala, horses • Full of symbiotic bacteria

38. Symbiosis • “living together”

39. Small intestine Stomach Cecum Colon (large intestine) Herbivore Cecum function • Fermentation chamber • Bacteria breakdown cellulose • Feces must be reingested