Which division of the trigeminal nerve primarily innervates the muscles of mastication?

• A. CN V2
• B. CN V1
• C. CN V3
• D. CN VII

Answer: (C)

The muscles of mastication are innervated by the motor component of the mandibular division of the trigeminal nerve. The trigeminal nerve splits into three divisions: V1 (ophthalmic), V2 (maxillary), and V3 (mandibular). V1 and V2 are primarily sensory, while V3 is mixed, providing motor fibers to the first pharyngeal arch muscles—the masseter, temporalis, and the medial and lateral pterygoids—as well as sensory fibers to the lower face. The facial nerve (CN VII) controls muscles of facial expression, not mastication. So, the division that primarily innervates the muscles of mastication is the mandibular division.