Glossopharyngeal nerve

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Nerve: Glossopharyngeal nerve

Plan of upper portions of glossopharyngeal, vagus, and accessory nerves.

Course and distribution of the glossopharyngeal, vagus, and accessory nerves. (Label for glossopharyngeal is at upper right.)
Latin	nervus glossopharyngeus
Gray's	subject #204 906
Innervates	stylopharyngeus
To	tympanic nerve
MeSH	Glossopharyngeal+Nerve
Dorlands/Elsevier	n_05/12565844

The glossopharyngeal nerve is the ninth of twelve cranial nerves. It exits the brainstem out from the sides of the upper medulla, just rostral (closer to the nose) to the vagus nerve.

1 Functions
2 Brainstem connections
3 Path
4 Testing the glossopharyngeal nerve
5 Additional images
6 External links

[edit] Functions

There are a number of functions of the glossopharyngeal nerve:

It receives sensory fibres from the posterior one-third of the tongue, the tonsils, the pharynx, the middle ear and the carotid body.
It supplies parasympathetic fibres to the parotid gland via the otic ganglion.
It supplies motor fibres to stylopharyngeus muscle
It contributes to the pharyngeal plexus.

[edit] Brainstem connections

The glossopharyngeal nerve, being mostly sensory, does not have a cranial nerve nucleus of its own. Instead it must project into many different structures in the brainstem:

Solitary nucleus: Taste from the posterior one-third of the tongue and information from carotid baroreceptors and carotid body chemoreceptors
Spinal nucleus of the trigeminal nerve: Visceral pain as well as somatic sensory fibers from the skin of the outer ear.
Nucleus ambiguus: The lower motor neurons for the stylopharyngeus muscle.
Inferior salivatory nucleus: Parasympathetic input to the parotid and mucous glands.

[edit] Path

From the medulla oblongata, the glossopharyngeal nerve passes laterally across the flocculus, and leaves the skull through the central part of the jugular foramen, in a separate sheath of the dura mater, lateral to and in front of the vagus and accessory nerves.

In its passage through the jugular foramen, it grooves the lower border of the petrous part of the temporal bone; and, at its exit from the skull, passes forward between the internal jugular vein and internal carotid artery; it descends in front of the latter vessel, and beneath the styloid process and the muscles connected with it, to the lower border of the stylopharyngeus.

It then curves forward, forming an arch on the side of the neck and lying upon the stylopharyngeus and middle pharyngeal constrictor muscle.

From there it passes under cover of the hyoglossus muscle, and is finally distributed to the palatine tonsil, the mucous membrane of the fauces and base of the tongue, and the mucous glands of the mouth.

[edit] Testing the glossopharyngeal nerve

The gag reflex is absent in patients with damage to the glossopharyngeal nerve as it is responsible for the afferent limb of the reflex.

[edit] Additional images

Dura mater and its processes exposed by removing part of the right half of the skull, and the brain.	Hind- and mid-brains; postero-lateral view.	Alveolar branches of superior maxillary nerve and sphenopalatine ganglion.	Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ.
Hypoglossal nerve, cervical plexus, and their branches.