Which cranial nerve provides parasympathetic innervation to the parotid gland?

• A. Glossopharyngeal (CN IX)
• B. Facial (CN VII)
• C. Vagus (CN X)
• D. Trigeminal (CN V)

Answer: (A)

Parasympathetic innervation to the parotid gland comes from the glossopharyngeal nerve. The preganglionic fibers originate in the inferior salivary nucleus in the medulla and travel with a branch of CN IX into the middle ear as the tympanic nerve, forming the tympanic plexus. They continue as the lesser petrosal nerve to reach the otic ganglion, where they synapse. The postganglionic fibers then ride with the auriculotemporal branch of the mandibular division of the trigeminal nerve to reach the parotid gland and drive its secretion.

Other nerves listed do not provide parasympathetic innervation to the parotid gland. The facial nerve is involved in parasympathetic supply to the lacrimal gland and to the submandibular/sublingual glands via different routes. The vagus nerve handles parasympathetic innervation to thoracic and abdominal organs. The trigeminal nerve is primarily somatic—sensory and motor to the face and muscles of mastication—not a parasympathetic conduit.