BIOL 3442 UTA POLLOCK DIGESTIVE SYSTEM EXAM 3: 200
COMPREHENSIVE QUESTIONS & RATIONALES
1. Which of the following is the primary enzyme secreted by the
salivary glands that initiates starch digestion?
A) Pepsin
B) Lipase
C) Amylase
D) Trypsin
CORRECT ANSWER: C) Amylase
Rationale: Salivary amylase is the primary enzyme in saliva that begins
the breakdown of starch into maltose. This enzyme works optimally at a
neutral pH and is responsible for initiating carbohydrate digestion in the
mouth.
2. Which structure prevents food from entering the nasal cavity during
swallowing?
A) Epiglottis
B) Uvula
C) Soft palate
D) Glottis
CORRECT ANSWER: B) Uvula
Rationale: The uvula is a fleshy extension at the back of the soft palate
that prevents food and liquid from entering the nasal cavity during
swallowing by helping to close off the nasopharynx.
,3. What is the primary function of the lower esophageal sphincter
(LES)?
A) To regulate the passage of food from the stomach to the duodenum
B) To prevent the reflux of gastric contents into the esophagus
C) To initiate the cephalic phase of digestion
D) To secrete intrinsic factor
CORRECT ANSWER: B) To prevent the reflux of gastric contents into
the esophagus
Rationale: The LES is a ring of smooth muscle at the junction of the
esophagus and stomach. Its primary function is to remain contracted to
prevent acidic gastric contents from refluxing back into the esophagus,
except during swallowing.
4. Which cells in the gastric glands are responsible for secreting
hydrochloric acid?
A) Chief cells
B) Parietal cells
C) G cells
D) Mucous neck cells
CORRECT ANSWER: B) Parietal cells
Rationale: Parietal cells, located in the gastric glands, secrete
hydrochloric acid (HCl) and intrinsic factor. HCl is essential for activating
pepsinogen and killing ingested bacteria.
5. The hormone gastrin, which stimulates gastric acid secretion, is
produced by which cells?
A) D cells
B) Enterochromaffin-like (ECL) cells
C) G cells
D) S cells
,CORRECT ANSWER: C) G cells
Rationale: G cells are located in the pyloric antrum of the stomach and
secrete gastrin in response to food intake, vagal stimulation, and an
alkaline pH. Gastrin then stimulates parietal cells to release HCl.
6. Which of the following is the inactive precursor of pepsin?
A) Trypsinogen
B) Chymotrypsinogen
C) Pepsinogen
D) Procarboxypeptidase
CORRECT ANSWER: C) Pepsinogen
Rationale: Chief cells secrete pepsinogen, an inactive zymogen. When it
encounters the acidic environment of the stomach (pH < 3), it is cleaved
to form active pepsin, which digests proteins.
7. What is the primary function of intrinsic factor (IF)?
A) To emulsify fats
B) To activate trypsinogen
C) To facilitate the absorption of vitamin B12 in the ileum
D) To neutralize stomach acid
CORRECT ANSWER: C) To facilitate the absorption of vitamin B12 in
the ileum
Rationale: Intrinsic factor is secreted by gastric parietal cells and binds
to vitamin B12. This complex is necessary for the absorption of B12 in
the terminal ileum. Lack of IF leads to pernicious anemia.
8. Which phase of gastric secretion is triggered by the sight, smell, or
thought of food?
A) Cephalic phase
B) Gastric phase
, C) Intestinal phase
D) Interdigestive phase
CORRECT ANSWER: A) Cephalic phase
Rationale: The cephalic phase is the first phase of digestion, mediated
by the vagus nerve in response to sensory stimuli (sight, smell, taste,
thought of food). It accounts for about 30% of gastric juice secretion.
9. The enterogastric reflex inhibits gastric emptying in response to
what stimuli in the duodenum?
A) Alkaline chyme, high fat, and high protein
B) Acidic chyme, high fat, and hypertonicity
C) Neutral chyme, low fat, and hypotonicity
D) Carbohydrate-rich chyme and low pH
CORRECT ANSWER: B) Acidic chyme, high fat, and hypertonicity
Rationale: The enterogastric reflex is triggered by the presence of acidic
chyme, fats, and hypertonic solutions in the duodenum. It inhibits
gastric motility and secretion to allow time for neutralization and
digestion in the small intestine.
10. Which of the following enzymes is responsible for the activation of
trypsinogen in the small intestine?
A) Pepsin
B) Enteropeptidase (enterokinase)
C) Chymotrypsin
D) Carboxypeptidase
CORRECT ANSWER: B) Enteropeptidase (enterokinase)
Rationale: Enteropeptidase, an enzyme secreted by the brush border of
the duodenum, cleaves trypsinogen to form active trypsin. Trypsin then
activates other pancreatic zymogens, including chymotrypsinogen and
procarboxypeptidase.
COMPREHENSIVE QUESTIONS & RATIONALES
1. Which of the following is the primary enzyme secreted by the
salivary glands that initiates starch digestion?
A) Pepsin
B) Lipase
C) Amylase
D) Trypsin
CORRECT ANSWER: C) Amylase
Rationale: Salivary amylase is the primary enzyme in saliva that begins
the breakdown of starch into maltose. This enzyme works optimally at a
neutral pH and is responsible for initiating carbohydrate digestion in the
mouth.
2. Which structure prevents food from entering the nasal cavity during
swallowing?
A) Epiglottis
B) Uvula
C) Soft palate
D) Glottis
CORRECT ANSWER: B) Uvula
Rationale: The uvula is a fleshy extension at the back of the soft palate
that prevents food and liquid from entering the nasal cavity during
swallowing by helping to close off the nasopharynx.
,3. What is the primary function of the lower esophageal sphincter
(LES)?
A) To regulate the passage of food from the stomach to the duodenum
B) To prevent the reflux of gastric contents into the esophagus
C) To initiate the cephalic phase of digestion
D) To secrete intrinsic factor
CORRECT ANSWER: B) To prevent the reflux of gastric contents into
the esophagus
Rationale: The LES is a ring of smooth muscle at the junction of the
esophagus and stomach. Its primary function is to remain contracted to
prevent acidic gastric contents from refluxing back into the esophagus,
except during swallowing.
4. Which cells in the gastric glands are responsible for secreting
hydrochloric acid?
A) Chief cells
B) Parietal cells
C) G cells
D) Mucous neck cells
CORRECT ANSWER: B) Parietal cells
Rationale: Parietal cells, located in the gastric glands, secrete
hydrochloric acid (HCl) and intrinsic factor. HCl is essential for activating
pepsinogen and killing ingested bacteria.
5. The hormone gastrin, which stimulates gastric acid secretion, is
produced by which cells?
A) D cells
B) Enterochromaffin-like (ECL) cells
C) G cells
D) S cells
,CORRECT ANSWER: C) G cells
Rationale: G cells are located in the pyloric antrum of the stomach and
secrete gastrin in response to food intake, vagal stimulation, and an
alkaline pH. Gastrin then stimulates parietal cells to release HCl.
6. Which of the following is the inactive precursor of pepsin?
A) Trypsinogen
B) Chymotrypsinogen
C) Pepsinogen
D) Procarboxypeptidase
CORRECT ANSWER: C) Pepsinogen
Rationale: Chief cells secrete pepsinogen, an inactive zymogen. When it
encounters the acidic environment of the stomach (pH < 3), it is cleaved
to form active pepsin, which digests proteins.
7. What is the primary function of intrinsic factor (IF)?
A) To emulsify fats
B) To activate trypsinogen
C) To facilitate the absorption of vitamin B12 in the ileum
D) To neutralize stomach acid
CORRECT ANSWER: C) To facilitate the absorption of vitamin B12 in
the ileum
Rationale: Intrinsic factor is secreted by gastric parietal cells and binds
to vitamin B12. This complex is necessary for the absorption of B12 in
the terminal ileum. Lack of IF leads to pernicious anemia.
8. Which phase of gastric secretion is triggered by the sight, smell, or
thought of food?
A) Cephalic phase
B) Gastric phase
, C) Intestinal phase
D) Interdigestive phase
CORRECT ANSWER: A) Cephalic phase
Rationale: The cephalic phase is the first phase of digestion, mediated
by the vagus nerve in response to sensory stimuli (sight, smell, taste,
thought of food). It accounts for about 30% of gastric juice secretion.
9. The enterogastric reflex inhibits gastric emptying in response to
what stimuli in the duodenum?
A) Alkaline chyme, high fat, and high protein
B) Acidic chyme, high fat, and hypertonicity
C) Neutral chyme, low fat, and hypotonicity
D) Carbohydrate-rich chyme and low pH
CORRECT ANSWER: B) Acidic chyme, high fat, and hypertonicity
Rationale: The enterogastric reflex is triggered by the presence of acidic
chyme, fats, and hypertonic solutions in the duodenum. It inhibits
gastric motility and secretion to allow time for neutralization and
digestion in the small intestine.
10. Which of the following enzymes is responsible for the activation of
trypsinogen in the small intestine?
A) Pepsin
B) Enteropeptidase (enterokinase)
C) Chymotrypsin
D) Carboxypeptidase
CORRECT ANSWER: B) Enteropeptidase (enterokinase)
Rationale: Enteropeptidase, an enzyme secreted by the brush border of
the duodenum, cleaves trypsinogen to form active trypsin. Trypsin then
activates other pancreatic zymogens, including chymotrypsinogen and
procarboxypeptidase.
