Embryology: development of the trigone: 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: development of the trigone

Sample item

On cystoscopy the triangular area at the base of the bladder is smooth, with the mucosa firmly attached to the muscle. From which structure does the mesodermal tissue of this region derive?

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

The answer and the reasoning

B. Absorbed mesonephric duct ends

As the caudal ends of the mesonephric ducts are absorbed into the bladder wall, they form the mesodermal trigone. The rest of the bladder derives from the endoderm of the vesical part of the urogenital sinus. The urachus becomes the median umbilical ligament at the apex.

Option by option

  • A. The urachus

    The urachus forms the median umbilical ligament, not the trigone.

  • B. Absorbed mesonephric duct ends (correct)

    Correct. The trigone is formed from absorbed mesonephric duct ends.

  • C. The paramesonephric ducts

    The paramesonephric ducts form the uterine tubes, uterus and upper vagina.

  • D. Endoderm of the urogenital sinus

    Urogenital sinus endoderm forms the remainder of the bladder lining and wall.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Absorbed mesonephric duct ends. As the caudal ends of the mesonephric ducts are absorbed into the bladder wall, they form the mesodermal trigone.

Why is "The urachus" not the answer?

The urachus forms the median umbilical ligament, not the trigone.

Why is "The paramesonephric ducts" not the answer?

The paramesonephric ducts form the uterine tubes, uterus and upper vagina.

Why is "Endoderm of the urogenital sinus" not the answer?

Urogenital sinus endoderm forms the remainder of the bladder lining and wall.

What concept does this question test?

It tests Embryology: development of the trigone in Anatomy. The rest of the bladder derives from the endoderm of the vesical part of the urogenital sinus. The urachus becomes the median umbilical ligament at the apex.

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: development of the trigone?

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.