Embryology: enteric nervous system: practice question

A Anatomy 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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Anatomy · Embryology: enteric nervous system

Sample item

A term newborn does not pass meconium for 48 hours and has abdominal distension. Contrast enema shows a narrow rectosigmoid with a dilated proximal colon, and rectal biopsy shows absent ganglion cells. What is the embryological basis?

ANon-rotation of the midgut loopBFailure of recanalisation of the rectumCFailure of the cloacal membrane to ruptureDFailure of neural crest cells to migrate into the distal colon

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

The answer and the reasoning

D. Failure of neural crest cells to migrate into the distal colon

Hirschsprung disease arises when neural crest-derived enteric neuroblasts fail to complete their craniocaudal migration (often RET mutation), so the Meissner and Auerbach plexuses are absent in the distal bowel. The aganglionic segment stays contracted, and the proximal colon dilates. Rectal biopsy with acetylcholinesterase staining confirms it.

Option by option

A. Non-rotation of the midgut loop
Non-rotation causes volvulus and bilious vomiting, with normal ganglion cells.
B. Failure of recanalisation of the rectum
Failure of recanalisation causes atresia or stenosis, with ganglia present.
C. Failure of the cloacal membrane to rupture
Failure of the cloacal membrane to rupture gives an imperforate anus.
D. Failure of neural crest cells to migrate into the distal colon (correct)
Correct. Failed neural crest migration leaves an aganglionic distal segment.

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.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Failure of neural crest cells to migrate into the distal colon. Hirschsprung disease arises when neural crest-derived enteric neuroblasts fail to complete their craniocaudal migration (often RET mutation), so the Meissner and Auerbach plexuses are absent in the distal bowel.

Why is "Non-rotation of the midgut loop" not the answer?

Non-rotation causes volvulus and bilious vomiting, with normal ganglion cells.

Why is "Failure of recanalisation of the rectum" not the answer?

Failure of recanalisation causes atresia or stenosis, with ganglia present.

Why is "Failure of the cloacal membrane to rupture" not the answer?

Failure of the cloacal membrane to rupture gives an imperforate anus.

What concept does this question test?

It tests Embryology: enteric nervous system in Anatomy. The aganglionic segment stays contracted, and the proximal colon dilates. Rectal biopsy with acetylcholinesterase staining confirms it.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Embryology: enteric nervous system?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.