Which nerve innervates the muscles innervates the muscles of mastication?

• A. Oculomotor nerve (CN III)
• B. Trigeminal nerve, mandibular division (CN V3)
• C. Facial nerve (CN VII)
• D. Glossopharyngeal nerve (CN IX)

Answer: (B)

Muscles of mastication are driven by motor fibers from the mandibular division of the trigeminal nerve. The trigeminal nerve has three divisions, and only the mandibular division carries motor innervation to these chewing muscles (masseter, temporalis, and the pterygoids), with additional motor branches like to the mylohyoid and anterior belly of the digastric. The other divisions are sensory and do not supply these muscles. For example, the oculomotor nerve controls most extraocular muscles, the facial nerve innervates muscles of facial expression, and the glossopharyngeal nerve supplies the stylopharyngeus and other functions—none of which provide the motor supply to the muscles involved in mastication.