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Animal Nutrition II (Ch. 41) Keywords • Roles of mouth, stomach, sm.&lg. Intestine in digestion • Pepsin, pepsinogen • Villi, microvilli • Cecum • Cellulose • Cellulase Stomach Digestive mechanisms in stomach • Mechanical • Chemical • enzymatic Mechanical • Mixing and churning Chemical • pH around 2 – Also breaks food down Enzymatic • Pepsin – Breaks down proteins Why doesn’t pepsin digest stomach? Activation of pepsin Small intestine • Most of the enzymatic digestion occurs here Table 41.13 p. 803 in Campbell Why doesn’t the small intestine digest itself? Fig. 37.13 Most nutrient absorption takes place in small intestine • Structure: another example of increasing surface area Structure of small intestine Microvilli Large intestine (colon) • Major function is to reabsorb water Here are a few review questions What would happen if you had a defect in pepsin production? 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 What would happen if you had a defect in salivary amylase production? 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 Which of the following would you least like to donate to science while you are still alive? • A. Cecum • B. Pancreas • C. Reproductive organs What would happen if you had a defect in small intestine enteropeptidase? Variations of vertebrate digestive system • Herbivorous mammals – Specialized fermentation chambers Coyote vs. Koala Why does herbivory require specializations? • Plant tissue – Harder to break up – Contains cellulose – Nutrients less concentrated than meat Structure of cellulose Only bacteria and protozoa can break down cellulose Via the enzyme cellulase Cecum • Pouch at junction between lg and sm intestine • Large cecum in rabbits, some rodents, koala, horses • Full of symbiotic bacteria Symbiosis • “living together” Cecum function • Fermentation chamber • Bacteria breakdown cellulose • Feces must be reingested