glossopharyngeal nerve

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

The glossopharyngeal nerve is the ninth (IX) of twelve pairs of cranial nerves (24 nerves total). It exits the brainstem out from the sides of the upper medulla, just rostral (closer to the nose) to the vagus nerve.

Functions

There are a number of functions of the glossopharyngeal nerve:

• It receives general sensory fibers (ventral trigeminothalamic tract) from the tonsils, the pharynx, the middle ear and the posterior 1/3 of the tongue.
• It receives special sensory fibers (taste) from the posterior one-third of the tongue.
• It receives visceral sensory fibers from the carotid bodies.
• It supplies parasympathetic fibers to the parotid gland via the otic ganglion.
• It supplies motor fibers to stylopharyngeus muscle, the only motor component of this cranial nerve.
• It contributes to the pharyngeal plexus.

Brainstem connections

The glossopharyngeal nerve is mostly sensory. The glossopharyngeal nerve also aids in tasting, swallowing and salivary secretions. Its superior and inferior (petrous) ganglia contain the cell bodies of pain fibers. It also projects 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: Somatic sensory fibers from the middle ear.
• Lateral Nucleus of Ala Cinerea: Visceral pain.
• Nucleus ambiguus: The lower motor neurons for the stylopharyngeus muscle.
• Inferior salivatory nucleus: Parasympathetic input to the parotid and mucous glands.

Path

From the medulla oblongata, the glossopharyngeal nerve passes laterally across or below the flocculus, and leaves the skull through the central part of the jugular foramen. From the superior and inferior ganglia in jugular foramen it has its own sheath of dura mater. The inferior ganglion on the inferior surface of petrous part of temporal is related with a triangular deppression into which the aqueduct of cochlea opens. Inferiorly the glossopharyngeal nerve is lateral and anterior to the vagus nerve and accessory nerve.

In its passage through the jugular foramen it passes 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.

Branches

• Tympanic
• Stylopharyngeal
• Tonsillar
• Nerve to carotid sinus
• Branches to the posterior third of tongue
• Lingual branches
• A communicating branch to the Vagus nerve

Note: The glossopharyneal nerve contributes in the formation of the pharyngeal plexus along with the vagus nerve.

Testing the glossopharyngeal nerve

The integrity of the glossopharyngeal nerve may be evaluated by testing the patient's general sensation and that of taste on the posterior third of the tongue.

Additional images

Inferior view of the human brain, with the cranial nerves labelled.	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.

External links

• NeuroNames hier-698
• MedEd at Loyola GrossAnatomy/h_n/cn/cn1/cn9.htm
• MedlinePlus Image 9350
• cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (IX)