Which nerve supply innervates the muscle labelled E?

Question

BlackTom AI · Accepted Answer

Label E corresponds to the anterior belly of the digastric (the small strap‑like muscle attaching to the digastric fossa of the mandible and passing posteroinferiorly to the hyoid). The key nerve supply fact: the mylohyoid nerve (a branch of the inferior alveolar nerve) supplies the anterior belly of the digastric and the mylohyoid; that nerve arises from the mandibular division (V3) of the trigeminal nerve.

1) Relevant knowledge points and concepts
- The trigeminal nerve (CN V) has three divisions: V1 (ophthalmic), V2 (maxillary), V3 (mandibular).
- V1 and V2 are purely sensory. V3 contains both sensory and motor fibers.
- Muscles of mastication and a few other head muscles (mylohyoid, anterior belly of digastric, tensor veli palatini, tensor tympani) receive motor innervation from branches of V3.
- The mylohyoid nerve branches from the inferior alveolar nerve (which is a branch of V3) and supplies the mylohyoid and anterior belly of digastric.

2) Complete reasoning process step by step
- Identify the muscle at label E anatomically: located at the anterior inferior mandible, straplike, directed toward the hyoid — consistent with anterior digastric (or mylohyoid area).
- Determine motor nerve for that muscle: anterior digastric and mylohyoid are supplied by the mylohyoid nerve.
- Trace the origin of that nerve: mylohyoid nerve ← inferior alveolar nerve ← mandibular division (CN V3).
- Therefore the motor innervation is provided by CN V3.

3) Intermediate steps (nerve pathway shown explicitly)
- CN V (trigeminal) → mandibular division (V3) → inferior alveolar nerve → mylohyoid branch → anterior belly of digastric / mylohyoid.

4) Why the correct answer is correct
- Because the anterior belly of the digastric/mylohyoid are unique among these submandibular muscles in receiving motor fibers from a branch of V3 (mylohyoid nerve). V3 is the only trigeminal division that carries motor fibers to these muscles.

5) Why other options are incorrect
- "1st division / CN V1 (ophthalmic)" and "2nd division / CN V2 (maxillary)" are purely sensory and do not supply motor innervation to muscles of the floor of the mouth or anterior digastric.
- "4th division / CN V4" is not an anatomical division of the trigeminal nerve and is therefore incorrect.

6) Conclusion confirming the final answer
- Therefore the muscle labeled E is innervated by the 3rd (mandibular) division of the trigeminal nerve (CN V3), which matches the provided correct answer.

Which nerve supply innervates the muscle labelled E?Single choice

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