Pelvis: autonomic innervation: 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: autonomic innervation

Sample item

A 26-year-old man has retroperitoneal lymph node dissection for testicular cancer. Afterwards erections are normal but no semen emerges at orgasm. Injury to which structure best explains this?

APudendal nerveBLumbar sympathetic chain and superior hypogastric plexus fibresCGenitofemoral nerveDPelvic splanchnic nerves (S2 to S4)

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

The answer and the reasoning

B. Lumbar sympathetic chain and superior hypogastric plexus fibres

Emission and closure of the bladder neck during ejaculation are sympathetic (L1 and L2) via the lumbar splanchnic nerves and hypogastric plexus. Injury during retroperitoneal dissection causes anejaculation or retrograde ejaculation with normal erections, which are parasympathetic (S2 to S4). Nerve-sparing techniques reduce this complication.

Option by option

A. Pudendal nerve
The pudendal nerve mediates the expulsion phase via the bulbospongiosus and sensation, and is not in the retroperitoneum.
B. Lumbar sympathetic chain and superior hypogastric plexus fibres (correct)
Correct. Sympathetic injury abolishes emission and bladder neck closure while sparing erection.
C. Genitofemoral nerve
The genitofemoral nerve gives the cremasteric reflex and has no role in ejaculation.
D. Pelvic splanchnic nerves (S2 to S4)
The pelvic splanchnic nerves mediate erection, which is preserved here.

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, Lumbar sympathetic chain and superior hypogastric plexus fibres. Emission and closure of the bladder neck during ejaculation are sympathetic (L1 and L2) via the lumbar splanchnic nerves and hypogastric plexus.

Why is "Pudendal nerve" not the answer?

The pudendal nerve mediates the expulsion phase via the bulbospongiosus and sensation, and is not in the retroperitoneum.

Why is "Genitofemoral nerve" not the answer?

The genitofemoral nerve gives the cremasteric reflex and has no role in ejaculation.

Why is "Pelvic splanchnic nerves (S2 to S4)" not the answer?

The pelvic splanchnic nerves mediate erection, which is preserved here.

What concept does this question test?

It tests Pelvis: autonomic innervation in Anatomy. Injury during retroperitoneal dissection causes anejaculation or retrograde ejaculation with normal erections, which are parasympathetic (S2 to S4). Nerve-sparing techniques reduce this complication.

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 Pelvis: autonomic innervation?

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.