Embryology: somite derivatives: 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: somite derivatives

Sample item

A child has selective weakness of the deep intrinsic muscles of the back. Which embryonic division of the myotome forms these muscles, and which ramus of the spinal nerve supplies them?

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

The answer and the reasoning

D. Epaxial division supplied by dorsal rami

Each myotome divides into a dorsal epaxial part, forming the extensor muscles of the vertebral column supplied by dorsal primary rami, and a ventral hypaxial part forming muscles of the body wall and limbs supplied by ventral primary rami. The sclerotome forms the vertebrae and the dermatome forms the dermis.

Option by option

  • A. Epaxial division supplied by ventral rami

    Epaxial muscles are not supplied by ventral rami.

  • B. Hypaxial division supplied by dorsal rami

    Hypaxial muscles are supplied by ventral rami, so this pairing is wrong.

  • C. Hypaxial division supplied by ventral rami

    Hypaxial muscles form lateral and anterior body wall muscles and are not the back extensors.

  • D. Epaxial division supplied by dorsal rami (correct)

    Correct. Epaxial muscles are the deep back muscles with dorsal ramus supply.

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, Epaxial division supplied by dorsal rami. Each myotome divides into a dorsal epaxial part, forming the extensor muscles of the vertebral column supplied by dorsal primary rami, and a ventral hypaxial part forming muscles of the body wall and limbs supplied by ventral primary rami.

Why is "Epaxial division supplied by ventral rami" not the answer?

Epaxial muscles are not supplied by ventral rami.

Why is "Hypaxial division supplied by dorsal rami" not the answer?

Hypaxial muscles are supplied by ventral rami, so this pairing is wrong.

Why is "Hypaxial division supplied by ventral rami" not the answer?

Hypaxial muscles form lateral and anterior body wall muscles and are not the back extensors.

What concept does this question test?

It tests Embryology: somite derivatives in Anatomy. The sclerotome forms the vertebrae and the dermatome forms the dermis.

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: somite derivatives?

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.