Which nerve provides motor innervation to the muscles derived from the first pharyngeal arch?

• A. CN VII
• B. CN IX
• C. CN V (V3)
• D. CN X

Answer: (C)

Motor innervation to the muscles derived from the first pharyngeal arch comes from the mandibular division of the trigeminal nerve (CN V3). This division carries the motor fibers that supply the arch 1 derivatives—the muscles of mastication (masseter, temporalis, medial and lateral pterygoids) as well as other first-arch muscles like the mylohyoid and tensor muscles. The other nerves map to other arches: CN VII to the second arch muscles (facial expression), CN IX to the third arch (stylopharyngeus), and CN X to the fourth and sixth arches. So CN V3 is the correct motor innervation for the first arch.