Glossopharyngeal nerve (IX)

At a glance

English

Glossopharyngeal nerve (IX)

Latin (TA2)

Nervus glossopharyngeus (IX)

System

Nerve

Region

Head

Side

Paired, left and right

About the glossopharyngeal nerve (ix)

Cranial nerve IX, the glossopharyngeal nerve, is named for its two main territories, the tongue and the pharynx. It is a mixed nerve with five kinds of fibre: motor to a single muscle, parasympathetic to the parotid gland, sensory from the carotid sinus and body, general sensory from the throat and ear, and taste from the back of the tongue.

Its rootlets leave the side of the upper medulla in the groove behind the olive, in front of the inferior cerebellar peduncle, just above those of the vagus. The nerve runs laterally, near the flocculus of the cerebellum, to leave the skull through the jugular foramen, in front of the vagus and accessory nerves and in its own sleeve of dura. Here it carries two sensory ganglia, superior and inferior; the inferior lies in a small notch on the petrous temporal bone. Below the skull it slips forwards between the great vein and artery of the neck, the internal jugular and internal carotid, descends in front of the artery deep to the styloid process, and winds around the back of stylopharyngeus. It then curves forwards on that muscle and the middle constrictor, passes deep to hyoglossus and ends in the tonsil, the fauces and the back of the tongue.

Its branches follow its functions. The tympanic nerve rises into the middle ear, forms a plexus on the promontory and continues as the lesser petrosal nerve, which leaves through the foramen ovale to the otic ganglion; postganglionic fibres ride on the auriculotemporal nerve into the parotid. The carotid sinus nerve carries pressure and chemical signals from the carotid bifurcation to the solitary nucleus for reflex control of blood pressure and breathing. Further branches go to stylopharyngeus, which lifts the pharynx in swallowing and speech, to the tonsil, to the pharyngeal plexus with the vagus, and to the hind third of the tongue, including the vallate papillae, for taste and touch.

The nerve provides the sensory side of the gag reflex, whose motor side is the vagus, so testing gagging, swallowing and taste on the back of the tongue checks it. Damage, often together with the vagus and accessory nerves at the jugular foramen, causes loss of taste and feeling over the back of the tongue and difficulty swallowing.

Course and supply

Arises from

Rootlets from the upper medulla in the groove behind the olive; its fibres come from the nucleus ambiguus, inferior salivatory nucleus, solitary nucleus and spinal trigeminal nucleus.

Ends in

Ends in tonsillar and lingual branches to the palatine tonsil, the fauces and the rear of the tongue, after giving the tympanic, carotid sinus, stylopharyngeal and pharyngeal branches.

Supplies

Motor to stylopharyngeus; secretomotor to the parotid, relayed in the otic ganglion; taste and general sensation from the tongue's posterior third; sensation from the pharynx, tonsil, middle ear and inner eardrum; afferent from the carotid body and the carotid sinus.