Embryology: bladder exstrophy: 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: bladder exstrophy

Sample item

A newborn has exposed bladder mucosa on the lower abdominal wall, a wide pubic symphysis and epispadias. What is the embryological basis?

AFailure of the urachus to obliterateBFailure of the genital folds to fuse on the ventral surfaceCFailure of the urorectal septum to divide the cloacaDFailure of mesenchyme to migrate into the lower abdominal wall

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

The answer and the reasoning

D. Failure of mesenchyme to migrate into the lower abdominal wall

In bladder exstrophy, the cloacal membrane overextends and prevents mesenchyme from migrating between the ectoderm and endoderm of the lower abdominal wall. The anterior bladder wall and abdominal wall fail to form. Epispadias and diastasis of the pubic bones accompany it.

Option by option

A. Failure of the urachus to obliterate
A patent urachus causes urine leaking from the umbilicus.
B. Failure of the genital folds to fuse on the ventral surface
Failure of genital fold fusion produces hypospadias, not exposure of the bladder.
C. Failure of the urorectal septum to divide the cloaca
Failure of urorectal septum division produces a cloacal malformation or fistulas.
D. Failure of mesenchyme to migrate into the lower abdominal wall (correct)
Correct. The infraumbilical wall fails to form because mesenchyme cannot migrate in.

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 mesenchyme to migrate into the lower abdominal wall. In bladder exstrophy, the cloacal membrane overextends and prevents mesenchyme from migrating between the ectoderm and endoderm of the lower abdominal wall.

Why is "Failure of the urachus to obliterate" not the answer?

A patent urachus causes urine leaking from the umbilicus.

Why is "Failure of the genital folds to fuse on the ventral surface" not the answer?

Failure of genital fold fusion produces hypospadias, not exposure of the bladder.

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

Failure of urorectal septum division produces a cloacal malformation or fistulas.

What concept does this question test?

It tests Embryology: bladder exstrophy in Anatomy. The anterior bladder wall and abdominal wall fail to form. Epispadias and diastasis of the pubic bones accompany 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: bladder exstrophy?

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.