Glossopharyngeal (IX) Nerve

From the jugular foramen, the nerve arches forward between the internal jugular vein and internal carotid artery, then passes deep to the styloid process, and curves behind the stylopharyngeus muscle (which it supplies) to the side of the pharynx. It pierces the superior constrictor muscle (or passes between this muscle and the middle constrictor) to enter the base of the tongue. It finally divides into branches that supply the mucous membrane over the posterior third of the tongue, fauces, palatine tonsil, and adjacent part of the pharynx and glands and vessels in these areas.

The lingual branches convey special and general sensations from the vallate papillae and the tongue behind the sulcus terminalis. These branches are associated with small lingual ganglia. The ganglia act as relay centers for the preganglionic and postganglionic vasomotor and secretomotor neurons. Another glossopharyngeal branch is the tympanic nerve (or Jacobson’s nerve), which arises from the inferior (petrous) ganglion and ascends through the tympanic canaliculus to the middle ear (tympanic cavity), where it contributes to the tympanic plexus and gives off the lesser petrosal nerve. The tympanic nerve contains sensory fibers that supply the middle ear, parasympathetic secretory fibers that serve the parotid gland, and sympathetic fibers that communicate with the carotid sinus. There are also communications with the auricular vagal branch, the superior vagal ganglion, the superior cervical sympathetic trunk ganglion, and the facial nerve. There is also a carotid sinus branch, a branch to supply the stylopharyngeus muscle, and several pharyngeal branches, which unite with similar vagal branches and sympathetic filaments to form a plexus on the surface of the pharynx.

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