The tympanic branch of CN IX and lesser petrosal nerves contribute to parasympathetic innervation of which gland?

• A. Sublingual gland
• B. Submandibular gland
• C. Parotid gland
• D. Small mucous glands

Answer: (C)

Parasympathetic secretomotor fibers to the parotid gland come from the glossopharyngeal nerve (CN IX). The tympanic branch, also known as Jacobson’s nerve, carries these preganglionic fibers into the middle ear to form the tympanic plexus. From there, the fibers continue as the lesser petrosal nerve and reach the otic ganglion, where they synapse. The postganglionic fibers then hitchhike with the auriculotemporal nerve to the parotid gland, stimulating saliva production. This pathway is specific to the parotid; the submandibular and sublingual glands receive parasympathetics via the facial nerve (chorda tympani) to the submandibular ganglion, while mucous glands in other areas receive different parasympathetic routes.