Digestive System Review


1. Differentiate between physical and chemical digestion and state the function of each. (physical - intosmaller pieces to increase surface area; mechanical - into smaller molecules for absorption)

2. How are the two stages of digestion related? (mechanical increases surface area for chemical)

3. Why are you able to swallow water while standing on your head? (peristalsis)

4. How do the teeth and tongue function in digestion? (teeth chew and tongue positions food in mouth)

5. What is the purpose of saliva? (lubricate, moisten, amylase)

6. What prevents self-digestion of the stomach? (mucus)

7. What is the combined effect of sphincter muscles and peristalsis in the stomach? (with sphinctersclosed, food is confined in stomach and subjected to churning and gastric juice)

8. What would be the result if the stomach did not have sphincter muscles? (food would not remain longenough to be digested; acid would splash into the esophagus)

9. Why is surface area important in the small intestine and what features increase it? (needed forabsorption; folds, villi, microvilli)

10. You might say that the small intestine is the most important organ of the digestive system. Why might you be justified in saying so? (most digestion and absorption occur here)

11. What happens to food molecules after being absorbed in the small intestine? (enter blood andcirculate to all cells)

12. What’s the deal with pepsinogen and pepsin? (pepsin would digest cells producing it so pepsinogen ismade instead; HCl activates it)

13. How is the small intestine protected from the acid chyme? From pepsin? (acid in small intestine secretin bicarbonate to neutralize acid; the change in pH also deactivates pepsin)

14. In cases of extreme obesity, surgical procedures can be used to control weight. For each, state the effect on the patient:

a) a section of the small intestine is removed. (less food absorbed therefore fewer calories)

b) the size of the stomach is reduced. (feel full sooner so eat less)

15. A person can live without a gallbladder but not without a liver. Explain. (gall bladder stores bile; fatswould be digested more slowly)

16. If the gall bladder is removed, why is the common bile duct left intact? (so bile can flow directly tothe intestine)

17. Explain how the backwash of bile into the stomach can cause stomach ulcers. (bile emulsifies mucus)

18. The incidence of colon cancer is highest in countries where people eat the greatest quantities of animal fats and proteins. Individuals who live in countries where cereal grains form the basic diet have a much lower incidence of colon cancer. What conclusion might you draw from these data? Can colon cancer be eliminated by a change in diet? (the fiber in plants helps reduce colon cancer by filling colon morequickly. Also, preservatives in meat may increase the risk. Cant be eliminated but can be reduced)

19. If a person were suffering from gallstones, what foods might they have difficulty digesting? (fats)

20. Why might a person with an obstructed bile duct develop jaundice? (accumulation of bile salts inblood)

21. You have just eaten a cheese sandwich and for the next several hours your digestive system will go to work. Discuss what happens to the large food molecules as they are chemically broken down into nutrients. Finally, explain how these nutrients are absorbed into the bloodstream.

22. A man has high levels of cholesterol in his blood. What dietary recommendations would you give him? (avoid fatty acids)

23. What is a calorie? (unit for measuring energy) What is a Calorie? (1000 calories; used by dietindustry)

24. What are the three types of large molecules we need in our diet? (carbohydrates, fat, protein)

25. What is the major source of starch in the North American diet? (plants) Fats? (animal products) Protein? (meat)

26. What dietary purpose does fat serve? (energy storage)

27. Why is fat well-suited for its role? (stores 2x the energy carbohydrates do)

28. Most plant proteins are incomplete. What must vegetarians do to ensure they get complete protein? (eat a variety of plant products)


Complete the following table

Nutrient

Digestion Begins

Digestion Completed

Carbohydrates

(mouth)

(small intestine)

Proteins

(stomach)

(small intestine)

Fats

(small intestine)

(small intestine)

Complete the following table

Organ

Enzyme(s)

Function of enzyme(s)

Mouth

(amylase)

(starch to simple sugars)

Stomach

(pepsin)

(proteins to smaller bits)

Pancreas

(amylase, lipase, trypsin)

(starch, fats - simple fats, protein - amino acids)

Small Intestine

(lactase)

(digest lactose)