BIOS 256 FINAL EXAM QUESTIONS AND ANSWERS — 150
Questions
Section 1: Digestive System (Questions 1-15)
1 In a patient with achlorhydria (absence of gastric acid secretion), which of the following changes would most
likely be observed in the duodenal lumen after a meal?
A) Increased activation of pancreatic lipase due to elevated pH
B) Decreased conversion of pepsinogen to pepsin, but normal protein digestion from pancreatic proteases
C) Impaired release of secretin due to failure to acidify the duodenum, leading to reduced pancreatic bicarbonate
secretion
D) Enhanced vitamin B12 absorption due to reduced acid degradation of intrinsic factor
Answer: C
Rationale: Secretin release from S cells is triggered by low duodenal pH (below 4.5). Achlorhydria prevents gastric
acid entry, so duodenal pH remains high, reducing secretin secretion and thus pancreatic bicarbonate output.
Option A is incorrect because lipase works optimally at pH 8, but activation requires colipase and bile salts, not pH
alone. Option B: protein digestion is impaired because pepsin is inactive, and pancreatic proteases are secreted as
zymogens requiring enterokinase activation, which is pH-dependent. Option D: vitamin B12 absorption requires
intrinsic factor, which is stable at neutral pH; achlorhydria does not degrade IF.
2 A researcher measures the electrical activity of interstitial cells of Cajal (ICC) in the small intestine. After
application of a drug that blocks voltage-gated sodium channels, the slow wave amplitude decreases by 60%.
Which of the following best explains this observation?
A) ICC slow waves are generated by sodium influx, and the drug reduces the upstroke velocity
B) The drug indirectly reduces calcium release from the sarcoplasmic reticulum in ICC
C) Slow waves are primarily due to L-type calcium channels, and sodium channel blockade hyperpolarizes the
membrane, reducing calcium channel opening
D) Voltage-gated sodium channels are responsible for the plateau phase of the slow wave
Answer: C
Rationale: ICC slow waves are generated by rhythmic oscillations of intracellular calcium, driven by IP3-mediated
calcium release and subsequent activation of calcium-activated chloride channels (CaCC) and/or nonselective
cation channels. The depolarization phase is due to these channels, not sodium channels. However, voltage-gated
sodium channels contribute to the resting membrane potential; blocking them causes hyperpolarization, which
reduces the likelihood of L-type calcium channel opening, thereby decreasing slow wave amplitude. Option A is
incorrect because slow waves are not sodium-dependent. Option B is indirect but not the primary mechanism.
Option D: plateau phase involves calcium channels, not sodium.
3 A patient with chronic pancreatitis undergoes a secretin stimulation test. After intravenous secretin, duodenal
fluid is collected. Which of the following findings would be most consistent with severe exocrine pancreatic
insufficiency?
A) High volume of duodenal fluid with low bicarbonate concentration and high amylase activity
B) Low volume of duodenal fluid with low bicarbonate concentration and low lipase activity
C) High volume of duodenal fluid with high bicarbonate concentration and normal trypsin activity
D) Low volume of duodenal fluid with high bicarbonate concentration and absent chymotrypsin activity
Answer: B
,Rationale: Secretin stimulates pancreatic ductal cells to secrete bicarbonate-rich fluid. In severe exocrine
insufficiency, both acinar cell enzyme secretion and ductal bicarbonate secretion are impaired. Thus, after secretin,
duodenal fluid volume is low, bicarbonate concentration is low, and enzyme activities (lipase, trypsin, etc.) are low.
Option A describes high enzyme activity, inconsistent with insufficiency. Option C describes normal function.
Option D: high bicarbonate is contradictory to ductal failure.
4 A drug that inhibits the sodium-glucose cotransporter SGLT1 in the small intestine is being tested. Which of the
following effects on glucose absorption is most likely?
A) Complete blockade of glucose absorption because SGLT1 is the only transporter for glucose in enterocytes
B) Reduction of glucose absorption by about 50% because GLUT2 mediates the remainder
C) No effect because glucose is absorbed paracellularly via solvent drag
D) Increased glucose absorption due to compensatory upregulation of GLUT5
Answer: B
Rationale: SGLT1 is the primary active transporter for glucose and galactose across the apical membrane of
enterocytes. However, after a meal, high luminal glucose concentrations also allow GLUT2 to be recruited to the
apical membrane, contributing to glucose uptake. Thus, SGLT1 inhibition reduces but does not eliminate glucose
absorption. Option A is false because GLUT2 provides an alternative route. Option C: paracellular absorption is
minor. Option D: GLUT5 transports fructose, not glucose.
5 A patient with a duodenal ulcer is found to have elevated serum gastrin levels. Which of the following
additional findings would most strongly suggest that the hypergastrinemia is due to a gastrinoma
(Zollinger-Ellison syndrome) rather than antral G-cell hyperplasia?
A) Basal acid output (BAO) greater than 15 mEq/h and a positive secretin stimulation test (increase in gastrin
>200 pg/mL)
B) Elevated gastrin after a meal, with normal BAO
C) Low pepsinogen I levels and negative secretin stimulation test
D) Gastrin response to intravenous calcium infusion that is blunted
Answer: A
Rationale: Zollinger-Ellison syndrome is characterized by autonomous gastrin secretion from a neuroendocrine
tumor, leading to high BAO and a paradoxical increase in gastrin after secretin (due to secretin receptors on tumor
cells). In contrast, antral G-cell hyperplasia shows a meal-stimulated gastrin increase and no response to secretin.
Option B is typical of G-cell hyperplasia. Option C: pepsinogen I is usually high in ZES. Option D: calcium
infusion stimulates gastrin release in both conditions, though more pronounced in ZES.
6 A researcher isolates enterocytes from the jejunum and measures the activity of the brush-border enzyme
lactase. The enzyme's Km for lactose is 5 mM, and Vmax is 100 nmol/min/mg protein. In the presence of a
competitive inhibitor (Ki = 2 mM) at a concentration of 4 mM, what is the apparent Km for lactose?
A) 5 mM
B) 10 mM
C) 15 mM
D) 20 mM
Answer: C
Rationale: For competitive inhibition, apparent Km = Km * (1 + [I]/Ki) = 5 mM * (1 + 4/2) = 5 * 3 = 15 mM. Vmax
remains unchanged. Thus, the correct answer is 15 mM. Option A is the uninhibited Km. Option B would be if
[I]=Ki. Option D is incorrect.
, 7 Which of the following best describes the role of the migrating motor complex (MMC) in the interdigestive
period?
A) It propels intestinal contents toward the colon and prevents bacterial overgrowth by sweeping residual debris
and bacteria
B) It stimulates gallbladder contraction to release bile for emulsification of residual fats
C) It increases intestinal permeability to facilitate absorption of nutrients from the previous meal
D) It coordinates with the ileal brake to delay gastric emptying
Answer: A
Rationale: The MMC is a cyclic pattern of motility that occurs during fasting, sweeping undigested material and
bacteria from the small intestine into the colon, thereby preventing bacterial overgrowth. Option B: gallbladder
contraction is stimulated by cholecystokinin (CCK) postprandially, not during MMC. Option C: MMC reduces
permeability. Option D: the ileal brake is a feedback mechanism that slows gastric emptying when nutrients reach
the ileum, not a function of MMC.
8 A patient with severe liver cirrhosis develops ascites and esophageal varices. Which of the following hormonal
changes is most likely contributing to the ascites?
A) Increased secretion of atrial natriuretic peptide (ANP) due to central volume expansion
B) Increased plasma renin activity and aldosterone levels due to reduced effective circulating volume
C) Decreased antidiuretic hormone (ADH) secretion due to impaired hepatic clearance
D) Elevated levels of vasoactive intestinal peptide (VIP) causing splanchnic vasodilation
Answer: B
Rationale: In cirrhosis, portal hypertension leads to splanchnic vasodilation and reduced effective arterial blood
volume, activating the renin-angiotensin-aldosterone system (RAAS). Aldosterone promotes sodium and water
retention, contributing to ascites. Option A: ANP levels are often normal or low in cirrhosis despite volume
overload due to blunted secretion. Option C: ADH is often increased due to non-osmotic stimulation, not
decreased. Option D: VIP levels are not typically elevated in cirrhosis.
9 A drug that selectively blocks the cystic fibrosis transmembrane conductance regulator (CFTR) in the intestinal
epithelium is administered. Which of the following would most likely occur?
A) Increased chloride secretion into the intestinal lumen, leading to diarrhea
B) Decreased chloride secretion, leading to constipation and reduced fluid in the lumen
C) Increased bicarbonate secretion due to compensatory upregulation of other transporters
D) Enhanced sodium absorption due to increased ENaC activity
Answer: B
Rationale: CFTR is the primary chloride channel in intestinal epithelial cells, responsible for chloride secretion that
drives fluid secretion. Blocking CFTR reduces chloride and fluid secretion, resulting in constipation and dry
luminal contents. Option A is opposite. Option C: bicarbonate secretion is also CFTR-dependent in some regions,
so it would decrease, not increase. Option D: ENaC activity is regulated independently; CFTR blockade may
actually reduce sodium absorption indirectly.
10 In a patient with chronic gastritis and pernicious anemia, which of the following pathophysiological
mechanisms is most directly responsible for the anemia?
A) Impaired iron absorption due to lack of gastric acid
B) Deficiency of intrinsic factor leading to vitamin B12 malabsorption
C) Autoimmune destruction of parietal cells causing reduced erythropoietin production
D) Folate deficiency due to bacterial overgrowth in the stomach
, Answer: B
Rationale: Pernicious anemia is caused by autoimmune destruction of parietal cells, leading to deficiency of intrinsic
factor, which is essential for vitamin B12 absorption in the ileum. B12 deficiency causes megaloblastic anemia.
Option A: iron absorption is reduced but leads to microcytic anemia, not pernicious anemia. Option C:
erythropoietin is produced by kidneys, not parietal cells. Option D: folate deficiency can cause megaloblastic
anemia but is not the primary mechanism in pernicious anemia.
11 A researcher investigates the effect of a novel compound on digestive motility. In an isolated segment of guinea
pig ileum, the compound causes a rapid, transient contraction followed by a prolonged relaxation. Pretreatment
with tetrodotoxin abolishes both phases, while atropine blocks only the contraction. Which of the following
best explains this observation?
A) The compound directly activates muscarinic receptors on smooth muscle and indirectly releases nitric oxide
from enteric neurons.
B) The compound directly stimulates nicotinic receptors on myenteric neurons, leading to acetylcholine release
and subsequent activation of inhibitory motor neurons.
C) The compound is a partial agonist at 5-HT3 receptors, causing desensitization and subsequent blockade of
excitatory neurotransmission.
D) The compound inhibits acetylcholinesterase, leading to accumulation of acetylcholine and overstimulation of
both muscarinic and nicotinic receptors.
Answer: B
Rationale: Tetrodotoxin blocks voltage-gated sodium channels, so its abolition of both phases indicates neural
involvement. Atropine blocks muscarinic receptors, eliminating the contraction but not the relaxation, suggesting
the relaxation is mediated by a non-cholinergic neurotransmitter (e.g., nitric oxide) released from inhibitory motor
neurons. Option B correctly describes a compound that first excites cholinergic neurons (causing contraction) and
then activates inhibitory neurons (causing relaxation).
12 A patient with chronic pancreatitis exhibits steatorrhea and weight loss. Fecal elastase-1 is low. Which of the
following additional findings is most likely to be present?
A) Elevated serum gastrin and decreased gastric acid secretion
B) Decreased serum cholecystokinin and increased gallbladder ejection fraction
C) Decreased serum trypsinogen and increased fecal fat content
D) Elevated serum vasoactive intestinal peptide and decreased stool pH
Answer: C
Rationale: Chronic pancreatitis leads to exocrine insufficiency, reducing trypsinogen (and other pancreatic enzymes)
in serum, and causing malabsorption of fat (steatorrhea). Thus, decreased serum trypsinogen and increased fecal fat
are expected. Option A suggests Zollinger-Ellison syndrome (gastrinoma), not pancreatitis. Option B: CCK is
usually normal or elevated in response to maldigestion; gallbladder ejection fraction may be normal. Option D:
VIPoma causes watery diarrhea, not steatorrhea.
13 Which of the following best describes the role of the cystic fibrosis transmembrane conductance regulator
(CFTR) in the pathogenesis of meconium ileus in newborns with cystic fibrosis?
A) Defective CFTR leads to reduced chloride secretion and increased sodium absorption, resulting in dehydrated,
viscous intestinal secretions that obstruct the distal ileum.
B) CFTR dysfunction causes hypersecretion of bicarbonate into the intestinal lumen, precipitating calcium and
forming insoluble plugs.
C) Loss of CFTR function impairs pancreatic enzyme secretion, leading to undigested meconium that
accumulates and causes obstruction.
Questions
Section 1: Digestive System (Questions 1-15)
1 In a patient with achlorhydria (absence of gastric acid secretion), which of the following changes would most
likely be observed in the duodenal lumen after a meal?
A) Increased activation of pancreatic lipase due to elevated pH
B) Decreased conversion of pepsinogen to pepsin, but normal protein digestion from pancreatic proteases
C) Impaired release of secretin due to failure to acidify the duodenum, leading to reduced pancreatic bicarbonate
secretion
D) Enhanced vitamin B12 absorption due to reduced acid degradation of intrinsic factor
Answer: C
Rationale: Secretin release from S cells is triggered by low duodenal pH (below 4.5). Achlorhydria prevents gastric
acid entry, so duodenal pH remains high, reducing secretin secretion and thus pancreatic bicarbonate output.
Option A is incorrect because lipase works optimally at pH 8, but activation requires colipase and bile salts, not pH
alone. Option B: protein digestion is impaired because pepsin is inactive, and pancreatic proteases are secreted as
zymogens requiring enterokinase activation, which is pH-dependent. Option D: vitamin B12 absorption requires
intrinsic factor, which is stable at neutral pH; achlorhydria does not degrade IF.
2 A researcher measures the electrical activity of interstitial cells of Cajal (ICC) in the small intestine. After
application of a drug that blocks voltage-gated sodium channels, the slow wave amplitude decreases by 60%.
Which of the following best explains this observation?
A) ICC slow waves are generated by sodium influx, and the drug reduces the upstroke velocity
B) The drug indirectly reduces calcium release from the sarcoplasmic reticulum in ICC
C) Slow waves are primarily due to L-type calcium channels, and sodium channel blockade hyperpolarizes the
membrane, reducing calcium channel opening
D) Voltage-gated sodium channels are responsible for the plateau phase of the slow wave
Answer: C
Rationale: ICC slow waves are generated by rhythmic oscillations of intracellular calcium, driven by IP3-mediated
calcium release and subsequent activation of calcium-activated chloride channels (CaCC) and/or nonselective
cation channels. The depolarization phase is due to these channels, not sodium channels. However, voltage-gated
sodium channels contribute to the resting membrane potential; blocking them causes hyperpolarization, which
reduces the likelihood of L-type calcium channel opening, thereby decreasing slow wave amplitude. Option A is
incorrect because slow waves are not sodium-dependent. Option B is indirect but not the primary mechanism.
Option D: plateau phase involves calcium channels, not sodium.
3 A patient with chronic pancreatitis undergoes a secretin stimulation test. After intravenous secretin, duodenal
fluid is collected. Which of the following findings would be most consistent with severe exocrine pancreatic
insufficiency?
A) High volume of duodenal fluid with low bicarbonate concentration and high amylase activity
B) Low volume of duodenal fluid with low bicarbonate concentration and low lipase activity
C) High volume of duodenal fluid with high bicarbonate concentration and normal trypsin activity
D) Low volume of duodenal fluid with high bicarbonate concentration and absent chymotrypsin activity
Answer: B
,Rationale: Secretin stimulates pancreatic ductal cells to secrete bicarbonate-rich fluid. In severe exocrine
insufficiency, both acinar cell enzyme secretion and ductal bicarbonate secretion are impaired. Thus, after secretin,
duodenal fluid volume is low, bicarbonate concentration is low, and enzyme activities (lipase, trypsin, etc.) are low.
Option A describes high enzyme activity, inconsistent with insufficiency. Option C describes normal function.
Option D: high bicarbonate is contradictory to ductal failure.
4 A drug that inhibits the sodium-glucose cotransporter SGLT1 in the small intestine is being tested. Which of the
following effects on glucose absorption is most likely?
A) Complete blockade of glucose absorption because SGLT1 is the only transporter for glucose in enterocytes
B) Reduction of glucose absorption by about 50% because GLUT2 mediates the remainder
C) No effect because glucose is absorbed paracellularly via solvent drag
D) Increased glucose absorption due to compensatory upregulation of GLUT5
Answer: B
Rationale: SGLT1 is the primary active transporter for glucose and galactose across the apical membrane of
enterocytes. However, after a meal, high luminal glucose concentrations also allow GLUT2 to be recruited to the
apical membrane, contributing to glucose uptake. Thus, SGLT1 inhibition reduces but does not eliminate glucose
absorption. Option A is false because GLUT2 provides an alternative route. Option C: paracellular absorption is
minor. Option D: GLUT5 transports fructose, not glucose.
5 A patient with a duodenal ulcer is found to have elevated serum gastrin levels. Which of the following
additional findings would most strongly suggest that the hypergastrinemia is due to a gastrinoma
(Zollinger-Ellison syndrome) rather than antral G-cell hyperplasia?
A) Basal acid output (BAO) greater than 15 mEq/h and a positive secretin stimulation test (increase in gastrin
>200 pg/mL)
B) Elevated gastrin after a meal, with normal BAO
C) Low pepsinogen I levels and negative secretin stimulation test
D) Gastrin response to intravenous calcium infusion that is blunted
Answer: A
Rationale: Zollinger-Ellison syndrome is characterized by autonomous gastrin secretion from a neuroendocrine
tumor, leading to high BAO and a paradoxical increase in gastrin after secretin (due to secretin receptors on tumor
cells). In contrast, antral G-cell hyperplasia shows a meal-stimulated gastrin increase and no response to secretin.
Option B is typical of G-cell hyperplasia. Option C: pepsinogen I is usually high in ZES. Option D: calcium
infusion stimulates gastrin release in both conditions, though more pronounced in ZES.
6 A researcher isolates enterocytes from the jejunum and measures the activity of the brush-border enzyme
lactase. The enzyme's Km for lactose is 5 mM, and Vmax is 100 nmol/min/mg protein. In the presence of a
competitive inhibitor (Ki = 2 mM) at a concentration of 4 mM, what is the apparent Km for lactose?
A) 5 mM
B) 10 mM
C) 15 mM
D) 20 mM
Answer: C
Rationale: For competitive inhibition, apparent Km = Km * (1 + [I]/Ki) = 5 mM * (1 + 4/2) = 5 * 3 = 15 mM. Vmax
remains unchanged. Thus, the correct answer is 15 mM. Option A is the uninhibited Km. Option B would be if
[I]=Ki. Option D is incorrect.
, 7 Which of the following best describes the role of the migrating motor complex (MMC) in the interdigestive
period?
A) It propels intestinal contents toward the colon and prevents bacterial overgrowth by sweeping residual debris
and bacteria
B) It stimulates gallbladder contraction to release bile for emulsification of residual fats
C) It increases intestinal permeability to facilitate absorption of nutrients from the previous meal
D) It coordinates with the ileal brake to delay gastric emptying
Answer: A
Rationale: The MMC is a cyclic pattern of motility that occurs during fasting, sweeping undigested material and
bacteria from the small intestine into the colon, thereby preventing bacterial overgrowth. Option B: gallbladder
contraction is stimulated by cholecystokinin (CCK) postprandially, not during MMC. Option C: MMC reduces
permeability. Option D: the ileal brake is a feedback mechanism that slows gastric emptying when nutrients reach
the ileum, not a function of MMC.
8 A patient with severe liver cirrhosis develops ascites and esophageal varices. Which of the following hormonal
changes is most likely contributing to the ascites?
A) Increased secretion of atrial natriuretic peptide (ANP) due to central volume expansion
B) Increased plasma renin activity and aldosterone levels due to reduced effective circulating volume
C) Decreased antidiuretic hormone (ADH) secretion due to impaired hepatic clearance
D) Elevated levels of vasoactive intestinal peptide (VIP) causing splanchnic vasodilation
Answer: B
Rationale: In cirrhosis, portal hypertension leads to splanchnic vasodilation and reduced effective arterial blood
volume, activating the renin-angiotensin-aldosterone system (RAAS). Aldosterone promotes sodium and water
retention, contributing to ascites. Option A: ANP levels are often normal or low in cirrhosis despite volume
overload due to blunted secretion. Option C: ADH is often increased due to non-osmotic stimulation, not
decreased. Option D: VIP levels are not typically elevated in cirrhosis.
9 A drug that selectively blocks the cystic fibrosis transmembrane conductance regulator (CFTR) in the intestinal
epithelium is administered. Which of the following would most likely occur?
A) Increased chloride secretion into the intestinal lumen, leading to diarrhea
B) Decreased chloride secretion, leading to constipation and reduced fluid in the lumen
C) Increased bicarbonate secretion due to compensatory upregulation of other transporters
D) Enhanced sodium absorption due to increased ENaC activity
Answer: B
Rationale: CFTR is the primary chloride channel in intestinal epithelial cells, responsible for chloride secretion that
drives fluid secretion. Blocking CFTR reduces chloride and fluid secretion, resulting in constipation and dry
luminal contents. Option A is opposite. Option C: bicarbonate secretion is also CFTR-dependent in some regions,
so it would decrease, not increase. Option D: ENaC activity is regulated independently; CFTR blockade may
actually reduce sodium absorption indirectly.
10 In a patient with chronic gastritis and pernicious anemia, which of the following pathophysiological
mechanisms is most directly responsible for the anemia?
A) Impaired iron absorption due to lack of gastric acid
B) Deficiency of intrinsic factor leading to vitamin B12 malabsorption
C) Autoimmune destruction of parietal cells causing reduced erythropoietin production
D) Folate deficiency due to bacterial overgrowth in the stomach
, Answer: B
Rationale: Pernicious anemia is caused by autoimmune destruction of parietal cells, leading to deficiency of intrinsic
factor, which is essential for vitamin B12 absorption in the ileum. B12 deficiency causes megaloblastic anemia.
Option A: iron absorption is reduced but leads to microcytic anemia, not pernicious anemia. Option C:
erythropoietin is produced by kidneys, not parietal cells. Option D: folate deficiency can cause megaloblastic
anemia but is not the primary mechanism in pernicious anemia.
11 A researcher investigates the effect of a novel compound on digestive motility. In an isolated segment of guinea
pig ileum, the compound causes a rapid, transient contraction followed by a prolonged relaxation. Pretreatment
with tetrodotoxin abolishes both phases, while atropine blocks only the contraction. Which of the following
best explains this observation?
A) The compound directly activates muscarinic receptors on smooth muscle and indirectly releases nitric oxide
from enteric neurons.
B) The compound directly stimulates nicotinic receptors on myenteric neurons, leading to acetylcholine release
and subsequent activation of inhibitory motor neurons.
C) The compound is a partial agonist at 5-HT3 receptors, causing desensitization and subsequent blockade of
excitatory neurotransmission.
D) The compound inhibits acetylcholinesterase, leading to accumulation of acetylcholine and overstimulation of
both muscarinic and nicotinic receptors.
Answer: B
Rationale: Tetrodotoxin blocks voltage-gated sodium channels, so its abolition of both phases indicates neural
involvement. Atropine blocks muscarinic receptors, eliminating the contraction but not the relaxation, suggesting
the relaxation is mediated by a non-cholinergic neurotransmitter (e.g., nitric oxide) released from inhibitory motor
neurons. Option B correctly describes a compound that first excites cholinergic neurons (causing contraction) and
then activates inhibitory neurons (causing relaxation).
12 A patient with chronic pancreatitis exhibits steatorrhea and weight loss. Fecal elastase-1 is low. Which of the
following additional findings is most likely to be present?
A) Elevated serum gastrin and decreased gastric acid secretion
B) Decreased serum cholecystokinin and increased gallbladder ejection fraction
C) Decreased serum trypsinogen and increased fecal fat content
D) Elevated serum vasoactive intestinal peptide and decreased stool pH
Answer: C
Rationale: Chronic pancreatitis leads to exocrine insufficiency, reducing trypsinogen (and other pancreatic enzymes)
in serum, and causing malabsorption of fat (steatorrhea). Thus, decreased serum trypsinogen and increased fecal fat
are expected. Option A suggests Zollinger-Ellison syndrome (gastrinoma), not pancreatitis. Option B: CCK is
usually normal or elevated in response to maldigestion; gallbladder ejection fraction may be normal. Option D:
VIPoma causes watery diarrhea, not steatorrhea.
13 Which of the following best describes the role of the cystic fibrosis transmembrane conductance regulator
(CFTR) in the pathogenesis of meconium ileus in newborns with cystic fibrosis?
A) Defective CFTR leads to reduced chloride secretion and increased sodium absorption, resulting in dehydrated,
viscous intestinal secretions that obstruct the distal ileum.
B) CFTR dysfunction causes hypersecretion of bicarbonate into the intestinal lumen, precipitating calcium and
forming insoluble plugs.
C) Loss of CFTR function impairs pancreatic enzyme secretion, leading to undigested meconium that
accumulates and causes obstruction.
