Abdomen: rectus sheath: 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: rectus sheath

Sample item

During a lower midline laparotomy, a surgeon finds that below the arcuate line the rectus abdominis lies directly on the transversalis fascia. Which arrangement of the rectus sheath explains this?

AAll three flat-muscle aponeuroses pass behind the muscleBThe internal oblique aponeurosis splits to enclose the muscle in both layersCOnly the transversus abdominis aponeurosis passes in front of the muscleDAll three flat-muscle aponeuroses pass in front of the muscle

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

The answer and the reasoning

D. All three flat-muscle aponeuroses pass in front of the muscle

Above the arcuate line the internal oblique aponeurosis splits, with one layer in front of and one behind the rectus, whereas the external oblique is in front and the transversus abdominis is behind. Below the arcuate line, about midway between the umbilicus and pubis, all three aponeuroses pass anterior to the muscle, so there is no posterior sheath. This leaves the muscle on transversalis fascia and peritoneum.

Option by option

A. All three flat-muscle aponeuroses pass behind the muscle
A posterior aponeurotic layer would leave the posterior sheath intact, which is not the case below the line.
B. The internal oblique aponeurosis splits to enclose the muscle in both layers
Splitting of the internal oblique aponeurosis is the arrangement above the arcuate line.
C. Only the transversus abdominis aponeurosis passes in front of the muscle
The internal and external oblique aponeuroses also pass in front below the arcuate line, so this is incomplete.
D. All three flat-muscle aponeuroses pass in front of the muscle (correct)
Correct. With all aponeuroses anterior, the posterior wall of the sheath is absent below the arcuate line.

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, All three flat-muscle aponeuroses pass in front of the muscle. Above the arcuate line the internal oblique aponeurosis splits, with one layer in front of and one behind the rectus, whereas the external oblique is in front and the transversus abdominis is behind.

Why is "All three flat-muscle aponeuroses pass behind the muscle" not the answer?

A posterior aponeurotic layer would leave the posterior sheath intact, which is not the case below the line.

Why is "The internal oblique aponeurosis splits to enclose the muscle in both…" not the answer?

Splitting of the internal oblique aponeurosis is the arrangement above the arcuate line.

Why is "Only the transversus abdominis aponeurosis passes in front of the mus…" not the answer?

The internal and external oblique aponeuroses also pass in front below the arcuate line, so this is incomplete.

What concept does this question test?

It tests Abdomen: rectus sheath in Anatomy. Below the arcuate line, about midway between the umbilicus and pubis, all three aponeuroses pass anterior to the muscle, so there is no posterior sheath. This leaves the muscle on transversalis fascia and peritoneum.

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: rectus sheath?

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.