1). All of the following have one-way digestive systems except
a). a nematode.
b). a planarian.
c). an earthworm.
d). a human.
2). Intestines of herbivores are _____________ compared to carnivores.
c). about the same size
d). less convoluted
3). When a mammal swallows, the food is prevented from going up into the nasal cavity by the
c). soft palate.
4). The first site of protein digestion in the digestive system is
a). in the mouth.
b). in the esophagus.
c). in the stomach.
d). in the small intestine.
5). How is the digestion of fats different from that of proteins and carbohydrates?
a). Fat digestion occurs in the small intestine, and the digestion of proteins and carbohydrates occurs in the stomach.
b). Fats are absorbed into the cells as fatty acids and monoglycerides but are then modified for absorption into the blood; amino acids and glucose are not modified further.
c). Fats enter the hepatic portal circulation, but digested proteins and carbohydrates enter the lymphatic system.
d). Digested fats are absorbed in the large intestine, and digested proteins and carbohydrates are absorbed in the small intestine.
6). The primary function of the large intestine is
a). the breakdown and absorption of fats.
b). the absorption of vitamin K.
c). the absorption of water.
d). the concentration of solid wastes.
7). The _____________ secretes digestive enzymes and bicarbonate solution into the small intestine to aid digestion.
d). All of these are correct.
8). Which of the following represents the action of insulin?
a). increases blood glucose levels by the hydrolysis of glycogen
b). increases blood glucose levels by stimulating glucagon production
c). decreases blood glucose levels by forming glycogen
d). increases blood glucose levels by promoting cellular uptake of glucose
9). Gastrin functions by
a). enhancing the secretion of HCl in the stomach.
b). enhancing the secretion of pepsinogen in the stomach.
c). a negative feedback loop.
d). all of these.
10). Essential organic substances that are used in only tiny amounts by the body are called
a). trace elements.
Test Your Visual Understanding
1). Match the following descriptions with the appropriate lettered structures:
i). site of sodium and vitamin K absorption
ii). contracts in response to CCK
iii). connects the mouth with the stomach
iv). serves as both an endocrine and an exocrine gland
v). releases brush border enzymes
vi). storage area at the end of the large intestine
vii). site of initial carbohydrate digestion
viii). secretes bile pigments and bile salts
ix). site of initial protein digestion
v)--g, small intestine
Apply Your Knowledge
1). The average length of the small intestine, when fully extended after death, is 6 meters, with a diameter of approximately 2.5 centimeters. Because of folds, villi, and microvilli, the surface area is 2,000,000 square centimeters. What percentage of increase is attributed to the folding, villi, and microvilli in the small intestine?
Answer: The small intestine is essentially a long cylinder and to calculate the surface area of a cylinder you multiply the length by the circumference, which in this case is:
600 cm x 2.5π = 4710 cm2
Now, to calculate the percentage of increase attributed to the folding, villi, and microvilli subtract the calculated surface area from the total surface area and divide by the calculated surface area:
2,000,000 – 4710 / 4710 = 424 or 42,400% larger
2). Many birds possess crops, although few mammals do. Suggest a reason for this difference between birds and mammals.
Answer: Birds feed their young with food they acquire from the environment. The adult bird consumes the food but stores it in her crop. When she returns to the nest, she regurgitates the food into the mouths of the fledglings. Mammals on the other hand feed their young with milk that is produced in the mother's mammary glands. Young feed by latching onto the mother's nipples and suck the milk. Mammals have no need for a crop in their digestive system because they don't feed their young in the same way as birds do.