The Digestive System 659
- During the gastric phase, the secretion of HCl and
pepsinogen is stimulated by
a. vagus nerve stimulation that originates in the brain.
b. polypeptides in the gastric lumen and by gastrin
secretion.
c. secretin and cholecystokinin from the duodenum.
d. all of these.
- The secretion of HCl by the stomach mucosa is inhibited by
a. neural reflexes from the duodenum.
b. the secretion of an enterogastrone from the duodenum.
c. the lowering of gastric pH.
d. all of these.
- The first organ to receive the bloodborne products of
digestion is
a. the liver. c. the heart.
b. the pancreas. d. the brain.
- Which of these statements about hepatic portal blood is
true?
a. It contains absorbed fat.
b. It contains ingested proteins.
c. It is mixed with bile in the liver.
d. It is mixed with blood from the hepatic artery in the liver.
- Absorption of salt and water is the principal function of
which region of the GI tract?
a. Esophagus d. Jejunum
b. Stomach e. Large intestine
c. Duodenum
- Cholecystokinin (CCK) is a hormone that stimulates
a. bile production.
b. release of pancreatic enzymes.
c. contraction of the gallbladder.
d. both a and b.
e. both b and c.
- Which of these statements about vitamin B 12 is false?
a. Lack of this vitamin can produce pernicious anemia.
b. Intrinsic factor is needed for absorption of vitamin B 12.
c. Damage to the gastric mucosa may lead to a deficiency in
vitamin B 12.
d. Vitamin B 12 is absorbed primarily in the jejunum.
- Which of these statements about starch digestion is false?
a. It begins in the mouth.
b. It occurs in the stomach.
c. It requires the action of pancreatic amylase.
d. It requires brush border enzymes for completion.
- Which of these statements about fat digestion and absorption
is false?
a. Emulsification by bile salts increases the rate of fat
digestion.
b. Triglycerides are hydrolyzed by the action of pancreatic
lipase.
c. Triglycerides are resynthesized from monoglycerides and
fatty acids in the intestinal epithelial cells.
d. Triglycerides, as particles called chylomicrons, are
absorbed into blood capillaries within the villi.
- Which of these statements about contraction of intestinal
smooth muscle is true?
a. It occurs automatically.
b. It is increased by parasympathetic nerve stimulation.
c. It produces segmentation.
d. All of these are true.
- Which of the following hormones stimulates the secretion of
histamine from the ECL cells?
a. Enterogastrone c. Secretin
b. Gastrin d. Cholecystokinin
- Which of the following food types is most effective at
provoking the intestinal phase of gastric regulation?
a. Fat d. Proteins
b. Starch e. Amino acids
c. Sugars
- Which of the following statements about the liver is false?
a. Its cells cannot regenerate when damaged.
b. It is the first organ to receive food molecules from the
intestine.
c. Its cells are in direct contact with the blood.
d. Arterial and venous bloods mix as they travel through the
sinusoids.
e. The liver produces the bile acids and the bile pigment.
Test Your Understanding
- Explain how the gastric secretion of HCl and pepsin is
regulated during the cephalic, gastric, and intestinal phases.
- Describe how pancreatic enzymes become activated in the
lumen of the intestine. Why are these mechanisms needed?
- Explain the function of bicarbonate in pancreatic juice. How
may peptic ulcers in the duodenum be produced?
- Describe the mechanisms that are believed to protect the
gastric mucosa from self-digestion. What factors might be
responsible for the development of a peptic ulcer in the
stomach?
- Explain why the pancreas is considered both an exocrine
and an endocrine gland. Given this information, predict what
effects tying of the pancreatic duct would have on pancreatic
structure and function.
- Explain how jaundice is produced when (a) the person has
gallstones, (b) the person has a high rate of red blood cell
destruction, and (c) the person has liver disease. In which
case(s) would phototherapy for the jaundice be effective?
Explain.
- Describe the steps involved in the digestion and absorption
of fat.
- Distinguish between chylomicrons, very-low-density
lipoproteins, low-density lipoproteins, and high-density
lipoproteins.
