Pelvis: anal canal: 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 · Pelvis: anal canal

Sample item

A 45-year-old man has painless bright red bleeding after defecation and a soft mass prolapsing through the anus that returns on its own. Examination shows a grade II internal haemorrhoid. Why is it painless?

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

The answer and the reasoning

D. The mucosa above the pectinate line has visceral innervation from the inferior hypogastric plexus

Above the pectinate line the anal canal is endodermal and has visceral nerve supply from the inferior hypogastric plexus, sensitive only to stretch. Below the line the inferior rectal nerve, a branch of the pudendal nerve, gives acute pain sensation. Internal haemorrhoids are thus painless unless they thrombose or strangulate.

Option by option

  • A. The lining above the pectinate line is stratified squamous epithelium, which is insensitive

    The epithelium above the line is columnar, and squamous epithelium below the line is highly sensitive.

  • B. Internal haemorrhoids drain by the inferior rectal vein, which has no pain fibres

    Internal haemorrhoids drain by the superior rectal vein into the portal system.

  • C. The mucosa above the pectinate line is supplied by the inferior rectal nerve

    The inferior rectal nerve supplies the area below the line and would cause pain.

  • D. The mucosa above the pectinate line has visceral innervation from the inferior hypogastric plexus (correct)

    Correct. Visceral nerves do not carry sharp pain from mucosal lesions.

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 D, The mucosa above the pectinate line has visceral innervation from the inferior hypogastric plexus. Above the pectinate line the anal canal is endodermal and has visceral nerve supply from the inferior hypogastric plexus, sensitive only to stretch.

Why is "The lining above the pectinate line is stratified squamous epithelium…" not the answer?

The epithelium above the line is columnar, and squamous epithelium below the line is highly sensitive.

Why is "Internal haemorrhoids drain by the inferior rectal vein, which has no…" not the answer?

Internal haemorrhoids drain by the superior rectal vein into the portal system.

Why is "The mucosa above the pectinate line is supplied by the inferior recta…" not the answer?

The inferior rectal nerve supplies the area below the line and would cause pain.

What concept does this question test?

It tests Pelvis: anal canal in Anatomy. Below the line the inferior rectal nerve, a branch of the pudendal nerve, gives acute pain sensation. Internal haemorrhoids are thus painless unless they thrombose or strangulate.

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 Pelvis: anal canal?

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.