Submandibular region: marginal mandibular nerve: 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 · Submandibular region: marginal mandibular nerve

Sample item

After excision of a submandibular gland, a 50-year-old woman has asymmetry of the smile, with the corner of the lower lip on the operated side failing to move down and out. Which nerve was injured?

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

The answer and the reasoning

C. Marginal mandibular branch of the facial nerve

The marginal mandibular branch of the facial nerve runs along the lower border of the mandible, deep to platysma, over the submandibular gland, and supplies depressor anguli oris and depressor labii inferioris. It is at risk in submandibular surgery, and the surgeon incises below the mandible and retracts it upwards. The lingual and hypoglossal nerves are also at risk deeper in the dissection.

Option by option

  • A. Temporal branch of the facial nerve

    The temporal branch supplies the frontalis and upper orbicularis oculi.

  • B. Cervical branch of the facial nerve

    The cervical branch supplies platysma, which would not alter the lip position.

  • C. Marginal mandibular branch of the facial nerve (correct)

    Correct. Injury paralyses the lower lip depressors.

  • D. Buccal branch of the facial nerve

    The buccal branch supplies buccinator and the muscles of the upper lip and cheek.

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 C, Marginal mandibular branch of the facial nerve. The marginal mandibular branch of the facial nerve runs along the lower border of the mandible, deep to platysma, over the submandibular gland, and supplies depressor anguli oris and depressor labii inferioris.

Why is "Temporal branch of the facial nerve" not the answer?

The temporal branch supplies the frontalis and upper orbicularis oculi.

Why is "Cervical branch of the facial nerve" not the answer?

The cervical branch supplies platysma, which would not alter the lip position.

Why is "Buccal branch of the facial nerve" not the answer?

The buccal branch supplies buccinator and the muscles of the upper lip and cheek.

What concept does this question test?

It tests Submandibular region: marginal mandibular nerve in Anatomy. It is at risk in submandibular surgery, and the surgeon incises below the mandible and retracts it upwards. The lingual and hypoglossal nerves are also at risk deeper in the dissection.

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 Submandibular region: marginal mandibular nerve?

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.