Gastrointestinal: cystic fibrosis and pancreatic secretion: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Gastrointestinal: cystic fibrosis and pancreatic secretion

Sample item

A 4-year-old boy with recurrent chest infections has bulky, greasy, foul-smelling stools and poor weight gain. Which pancreatic abnormality causes the malabsorption?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Defective CFTR chloride channel in duct cells reduces fluid and bicarbonate secretion, so thick secretions block the ducts

In cystic fibrosis the CFTR defect impairs chloride and bicarbonate secretion by ductal epithelium, so the pancreatic secretion becomes viscous and dehydrated. Enzymes are trapped in the ducts, which obstruct and scar the gland, causing steatorrhoea and fat-soluble vitamin deficiency.

Option by option

  • A. Failure of acinar cells to synthesise any zymogens

    Acinar cells can synthesise zymogens, but the secretions cannot leave the blocked ducts.

  • B. Absence of enteropeptidase in the duodenal brush border

    Enteropeptidase deficiency is a rare cause of malabsorption and does not explain the chest infections.

  • C. Failure of the ileum to reabsorb bile salts

    Bile salt malabsorption follows ileal disease and is not the defect in cystic fibrosis.

  • D. Defective CFTR chloride channel in duct cells reduces fluid and bicarbonate secretion, so thick secretions block the ducts (correct)

    Correct. Reduced ductal fluid and bicarbonate cause obstruction and exocrine insufficiency.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Defective CFTR chloride channel in duct cells reduces fluid and bicarbonate secretion, so thick secretions block the ducts. In cystic fibrosis the CFTR defect impairs chloride and bicarbonate secretion by ductal epithelium, so the pancreatic secretion becomes viscous and dehydrated.

Why is "Failure of acinar cells to synthesise any zymogens" not the answer?

Acinar cells can synthesise zymogens, but the secretions cannot leave the blocked ducts.

Why is "Absence of enteropeptidase in the duodenal brush border" not the answer?

Enteropeptidase deficiency is a rare cause of malabsorption and does not explain the chest infections.

Why is "Failure of the ileum to reabsorb bile salts" not the answer?

Bile salt malabsorption follows ileal disease and is not the defect in cystic fibrosis.

What concept does this question test?

It tests Gastrointestinal: cystic fibrosis and pancreatic secretion in Physiology. Enzymes are trapped in the ducts, which obstruct and scar the gland, causing steatorrhoea and fat-soluble vitamin deficiency.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Gastrointestinal: cystic fibrosis and pancreatic secretion?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.