Glossopharyngeal Nerve / Anatomy / Cranial Nerve IX / XI Cranial nerve / Functional components
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Glossopharyngeal nerve
Glossopharyngeal nerve is the 9th cranial nerve. It is a mixed nerve, i.e., composed of both the motor and sensory fibres, but predominantly it is sensory. It derives its name from the fact that it provides sensory innervation to the tongue and pharynx.
Functional Components and Nuclei
1. Special visceral efferent fibres: They supply the stylopharyngeus muscle. They arise from nucleus ambiguus.
2. General visceral efferent fibres: They supply the secretomotor fibres to the parotid gland. They are preganglionic parasympathetic fibres and arise from the inferior salivatory nucleus.
3. Special visceral afferent fibres: They carry taste sensations from the posterior one-third of tongue including vallate papillae and terminate in the nucleus tractus solitarius.
4. General visceral afferent fibres: They carry general sensations of pain, touch, and temperature from the mucous membrane of the pharynx, tonsil, soft palate, and the posterior one-third of tongue and terminate in
the dorsal nucleus of the vagus.
5. General somatic afferent fibres: They carry proprioceptive sensations from the stylopharyngeus and skin of the auricle and terminate in the nucleus of the spinal tract of 5th nerve.
Course and Relations
The glossopharyngeal nerve arises from the upper part of the lateral aspect of the medulla between the olive and the inferior cerebellar peduncle. Then it leave the cranial cavity by passing through the jugular foramen.
The superior and inferior sensory ganglia are located on the nerve as it passes through the jugular foramen.
The smaller superior ganglion lies within the jugular foramen and is considered the detached part of the inferior ganglion.
The larger inferior ganglion lies just below the jugular foramen and contains the cell bodies of most of the sensory fibres of the nerve.
After emerging from the jugular foramen at the base of the skull, the nerve passes downward and forward between the ICA and the IJV. It then descends anterior to the internal carotid artery to the styloid process and muscles attached to it, to reach the lower border of the stylopharyngeus. From here it passes along with the
stylopharyngeus through the gap between the superior and middle constrictors of the pharynx. It then curves forward along the lateral aspect of the stylopharyngeus muscle which it supplies, and then passes deep to the stylohyoid ligament and posterior edge of the hyoglossus muscle. Here it breaks up into terminal branches, which supply the mucous membrane of the posterior one third of the tongue, pharynx, and tonsil.
Branches and Distribution
1. Tympanic branch (Jacobson’s nerve): It leaves the inferior ganglion and enters the middle ear through the tympanic canaliculus situated at the bony edge between the jugular foramen and carotid canal. It forms the
tympanic plexus over the promontory of the middle ear.
The tympanic plexus gives off:
(a) the lesser petrosal nerve and
(b) twigs to tympanic cavity, auditory tube
The lesser petrosal nerve carries the preganglionic parasympathetic fibres which relay in the otic ganglion. The postganglionic fibres from the ganglion supply the parotid gland.
2. Carotid nerve (nerve of Herring): It is a branch to carotid sinus and carotid body. It serves as an afferent limb for pressoreceptor and chemoreceptor reflexes from the carotid sinus and carotid body to regulate the heart rate and respiration, respectively.
3. Pharyngeal branch: It joins the pharyngeal branches of the vagus and the cervical sympathetic chain to form the pharyngeal plexus on the middle constrictor of the pharynx.
4. Branch to stylopharyngeus: It is the only motor branch of the glossopharyngeal nerve.
5. Tonsillar branches: They supply the mucous membrane of tonsil, fauces, and palate.
6. Lingual branches: They supply the posterior one-third of the tongue and vallate papillae and convey taste and general sensations.
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Dr. Ankit Jain
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