Abdomen and pelvis: internal anal sphincter: 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 · Abdomen and pelvis: internal anal sphincter

Sample item

In chronic anal fissure with a hypertonic sphincter, a lateral sphincterotomy divides part of an involuntary muscle ring that is the thickened lower end of the circular muscle of the rectum. Which muscle is this?

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

The answer and the reasoning

B. Internal anal sphincter

The internal anal sphincter is smooth muscle, formed by thickening of the circular coat of the rectum, and is under autonomic control. Its hypertonia contributes to pain and ischaemia of the posterior anal fissure. The external sphincter and puborectalis are striated, voluntary muscle.

Option by option

  • A. Conjoint longitudinal muscle

    This is the fused longitudinal muscle layer and fascia that passes between the sphincters, not the circular thickening.

  • B. Internal anal sphincter (correct)

    Correct. This smooth muscle ring is the thickened circular layer and is involuntary.

  • C. Deep external anal sphincter

    This is striated voluntary muscle supplied by the inferior rectal nerve.

  • D. Puborectalis

    This striated sling forms part of levator ani and maintains the anorectal angle.

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.

More Anatomy questions

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Internal anal sphincter. The internal anal sphincter is smooth muscle, formed by thickening of the circular coat of the rectum, and is under autonomic control.

Why is "Conjoint longitudinal muscle" not the answer?

This is the fused longitudinal muscle layer and fascia that passes between the sphincters, not the circular thickening.

Why is "Deep external anal sphincter" not the answer?

This is striated voluntary muscle supplied by the inferior rectal nerve.

Why is "Puborectalis" not the answer?

This striated sling forms part of levator ani and maintains the anorectal angle.

What concept does this question test?

It tests Abdomen and pelvis: internal anal sphincter in Anatomy. Its hypertonia contributes to pain and ischaemia of the posterior anal fissure. The external sphincter and puborectalis are striated, voluntary muscle.

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 Abdomen and pelvis: internal anal sphincter?

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.