Which letter is labelling a muscle that is innervated by a division of the trigeminal nerve / CN V?

Question

BlackTom AI · Accepted Answer

The masseter (label E) is a principal muscle of mastication and is innervated by the mandibular division (V3) of the trigeminal nerve (CN V).

1) Relevant knowledge points and concepts
- CN V (trigeminal) has three divisions: V1 (ophthalmic, sensory), V2 (maxillary, sensory), V3 (mandibular, mixed sensory and motor).
- Motor fibers of CN V are only carried in V3 and supply the muscles of mastication: masseter, temporalis, medial and lateral pterygoids, plus a few others (mylohyoid/anterior belly of digastric via nerve to mylohyoid, tensor tympani, tensor veli palatini).

2) Step-by-step reasoning
- Examine each labeled muscle region in the image and identify the muscle based on location and appearance.
- Label E lies over the lateral aspect of the mandible, a bulky rectangular muscle that elevates the mandible — morphology and position consistent with the masseter.
- Because the masseter is one of the classical muscles of mastication, its motor supply comes from V3.

3) Intermediate identification steps (anatomical cues)
- Masseter: superficial, lateral jaw, thick muscle fibers from zygomatic arch to mandibular ramus/coronoid process — matches E.
- Other visible muscles: a label near the cheek/oral angle (likely buccinator or orbicularis oris) is superficial facial muscle group; posterior neck labels correspond to sternocleidomastoid/trapezius or deeper posterior neck muscles.

4) Why the correct answer is correct
- E identifies the masseter, which is innervated by motor branches of the mandibular division (V3) of CN V, therefore E is innervated by a division of the trigeminal nerve.

5) Why the other options are incorrect
- D corresponds to a facial expression muscle (buccinator/zygomatic/orbicularis group) innervated by the facial nerve (CN VII), not CN V.
- A and B are posterior neck/scalp muscles (sternocleidomastoid, trapezius, or splenius group) innervated mainly by spinal accessory (CN XI) or cervical spinal nerves, not trigeminal V3.
- Any temporalis muscle (if present more superiorly) would also be innervated by V3, but that label is not the option given; the image’s E is the clear V3-innervated masseter.

6) Conclusion
Label E is the masseter and is innervated by the mandibular division (V3) of the trigeminal nerve; this confirms the provided correct answer E.

Which letter is labelling a muscle that is innervated by a division of the trigeminal nerve / CN V?单项选择题

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