The trigeminal motor nucleus is associated with which muscles?

• A. Muscles of mastication/chewing
• B. Muscles of facial expression
• C. Tongue muscles
• D. Neck muscles

Answer: (A)

The key idea is that the trigeminal motor nucleus supplies motor innervation to muscles derived from the first pharyngeal arch—the muscles of mastication. This nucleus sends motor fibers to the masseter, temporalis, and the medial and lateral pterygoids, enabling chewing. It also contributes to the tiny muscles tensor tympani and tensor veli palatini, which are related to hearing and swallowing but aren’t the primary movers in chewing.

In contrast, the muscles of facial expression are controlled by the facial nerve, not the trigeminal motor nucleus; tongue muscles are controlled by the hypoglossal nerve; and neck muscles are innervated by the spinal accessory nerve (and cervical nerves). So the trigeminal motor nucleus is associated with the muscles used for chewing.