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 full-term neonate has not passed meconium for 48 hours and has abdominal distension. A rectal examination is followed by an explosive release of stool and gas. A suction rectal biopsy shows absent ganglion cells. Which embryological failure explains this?

AFailure of recanalisation of the gut tubeBFailure of craniocaudal migration of neural crest cells into the gut wallCFailure of midgut rotationDFailure of the urorectal septum to divide the cloaca

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

The answer and the reasoning

B. Failure of craniocaudal migration of neural crest cells into the gut wall

Neural crest cells migrate along the gut in a craniocaudal direction to form the myenteric and submucosal plexuses. If migration stops, the distal bowel remains aganglionic and fails to relax, so a functional obstruction results. Mutations in the RET gene are the most common genetic cause of Hirschsprung disease.

Option by option

A. Failure of recanalisation of the gut tube
Failure of recanalisation causes atresia or stenosis, and ganglion cells would be present.
B. Failure of craniocaudal migration of neural crest cells into the gut wall (correct)
Correct. Arrested neural crest migration leaves the distal gut without ganglion cells.
C. Failure of midgut rotation
Malrotation causes volvulus with bilious vomiting and ganglion cells would be present.
D. Failure of the urorectal septum to divide the cloaca
Failure of the urorectal septum causes anorectal malformations, which would be visible on examination.

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 B, Failure of craniocaudal migration of neural crest cells into the gut wall. Neural crest cells migrate along the gut in a craniocaudal direction to form the myenteric and submucosal plexuses.

Why is "Failure of recanalisation of the gut tube" not the answer?

Failure of recanalisation causes atresia or stenosis, and ganglion cells would be present.

Why is "Failure of midgut rotation" not the answer?

Malrotation causes volvulus with bilious vomiting and ganglion cells would be present.

Why is "Failure of the urorectal septum to divide the cloaca" not the answer?

Failure of the urorectal septum causes anorectal malformations, which would be visible on examination.

What concept does this question test?

It tests Embryology: enteric nervous system in Anatomy. If migration stops, the distal bowel remains aganglionic and fails to relax, so a functional obstruction results. Mutations in the RET gene are the most common genetic cause of Hirschsprung disease.

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 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.