The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a

cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

that exits the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

from the sides of the upper medulla, just anterior (closer to the

nose A nose is a sensory organ and respiratory structure in vertebrates. It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils, or nares, a pair of tubes providing airflow through the ...

) to the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

nic

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...

, whereas the sensory division originates from the

cranial neural crest The cranial neural crest is one of the four regions of the neural crest. The cranial neural crest arises in the anterior and populates the face and the pharyngeal arches giving rise to bones, cartilage, nerves and connective tissue. The endocraniu ...

Structure

From the anterior portion of the

, the glossopharyngeal nerve passes laterally across or below the flocculus, and leaves the skull through the central part of the

jugular foramen A jugular foramen is one of the two (left and right) large foramina (openings) in the base of the skull, located behind the carotid canal. It is formed by the temporal bone and the occipital bone. It allows many structures to pass, including the ...

. 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 depression into which the aqueduct of cochlea opens. On the inferior side, the glossopharyngeal nerve is lateral and anterior to the

and

accessory nerve The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerv ...

. In its passage through the foramen (with X and XI), the glossopharyngeal nerve passes between the

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posteri ...

and

internal carotid artery The internal carotid artery is an artery in the neck which supplies the anterior cerebral artery, anterior and middle cerebral artery, middle cerebral circulation. In human anatomy, the internal and external carotid artery, external carotid ari ...

. It descends in front of the latter vessel and beneath the styloid process and the muscles connected with it, to the posterior lower border of the

stylopharyngeus muscle The stylopharyngeus muscle is a muscle in the head. It originates from the temporal styloid process. Some of its fibres insert onto the thyroid cartilage, while others end by intermingling with proximal structures. It is innervated by the glosso ...

. It then curves forward, forming an arch on the side of the neck and lying upon the

stylopharyngeus The stylopharyngeus muscle is a muscle in the head. It originates from the temporal styloid process. Some of its fibres insert onto the thyroid cartilage, while others end by intermingling with proximal structures. It is innervated by the glosso ...

and

middle pharyngeal constrictor The middle pharyngeal constrictor is a fan-shaped muscle located in the neck. It is one of three pharyngeal constrictor muscles. It is smaller than the inferior pharyngeal constrictor muscle. The middle pharyngeal constrictor originates from th ...

muscle. From there, it passes under cover of the

hyoglossus The hyoglossus is a thin and quadrilateral extrinsic muscle of the tongue. It originates from the hyoid bone; it inserts onto the side of the tongue. It is innervated by the hypoglossal nerve (cranial nerve XII). It acts to depress and retract th ...

muscle and is finally distributed to the

palatine tonsil Palatine tonsils, commonly called the tonsils and occasionally called the faucial tonsils, are tonsils located on the left and right sides at the back of the throat in humans and other mammals, which can often be seen as flesh-colored, pinkish ...

, the

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

of the fauces and base of the

tongue The tongue is a Muscle, muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper s ...

, and the serous glands of the

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

Branches

tympanic nerve The tympanic nerve ( Jacobson's nerve) is a branch of the glossopharyngeal nerve passing through the petrous part of the temporal bone to reach the middle ear. It provides sensory innervation for the middle ear, the Eustachian tube, the parotid ...

* stylopharyngeal nerve * tonsillar nerve * carotid sinus nerve * Branches to the posterior third of tongue * lingual branches * A communicating branch to the

Note: The glossopharyngeal nerve contributes in the formation of the pharyngeal plexus along with the vagus nerve. The glossopharyngeal nerve has five distinct general functions: #Branchial motor ( special visceral efferent)supplies the

. #Visceral motor ( general visceral efferent)provides

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The autonomic nervous system is responsible for regulat ...

innervation of the

parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the m ...

via the otic ganglion #Visceral sensory ( general visceral afferent)carries visceral sensory information from the

carotid sinus In human anatomy, the carotid sinus is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid at the level of the superior border of thyroid cartilage. The carot ...

and carotid body. #General sensory ( general somatic afferent)provides general sensory information from inner surface of the

tympanic membrane In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pressur ...

, upper

pharynx The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...

(GVA), and the posterior one-third of the

. #Visceral afferent ( special visceral afferent)provides

taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste. Taste is the perception stimulated when a substance in the mouth biochemistry, reacts chemically with taste receptor cells l ...

sensation from the posterior one-third of the

, including circumvallate papillae. The glossopharyngeal nerve as noted above is a mixed nerve consisting of both sensory and motor nerve fibers. The sensory fibers' origin include the pharynx, middle ear, posterior one-third of the tongue (including taste buds); and the carotid body and sinus. These fibers terminate at the

. The motor fibers' origin is the medulla oblongata, and they terminate at the parotid salivary gland, the glands of the posterior tongue, and the

muscle (which dilates the pharynx during swallowing).

Overview of branchial motor component

The branchial motor component of CN IX provides voluntary control of the stylopharyngeus muscle, which elevates the pharynx during swallowing and speech. Origin and central course The branchial motor component originates from the

nucleus ambiguus The nucleus ambiguus ("ambiguous nucleus" in English) is a group of large motor neurons, situated deep in the medullary part of the reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of neurons that innerva ...

in the reticular formation of the rostral medulla. Fibers leaving the nucleus ambiguus travel anteriorly and laterally to exit the medulla, along with the other components of CN IX, between the olive and the

inferior cerebellar peduncle The inferior cerebellar peduncle is formed by fibers of the restiform body that join with fibers from the much smaller juxtarestiform body. The inferior cerebellar peduncle is the smallest of the three cerebellar peduncles. The upper part of t ...

. Intracranial course Upon emerging from the lateral aspect of the medulla the branchial motor component joins the other components of CN IX to exit the skull via the jugular foramen. The glossopharyngeal fibers travel just anterior to the cranial nerves X and XI, which also exit the skull via the

. Extra-cranial course and final innervation Upon exiting the skull the branchial motor fibers descend deep to the

temporal styloid process The temporal styloid process is a slender bony process of the temporal bone extending downward and forward from the undersurface of the temporal bone just below the ear. The styloid process gives attachments to several muscles, and ligaments. Str ...

and wrap around the posterior border of the

before innervating it. Voluntary control of the stylopharyngeus muscle Signals for the voluntary movement of

originate in the pre-motor and motor cortex (in association with other cortical areas) and pass via the corticobulbar tract in the genu of the internal capsule to synapse bilaterally on the ambiguus nuclei in the medulla.

Overview of visceral motor component

Parasympathetic component of the glossopharyngeal nerve that innervates the ipsilateral parotid gland. Origin and central course The

preganglionic In the autonomic nervous system, nerve fibers from the central nervous system to the autonomic ganglion, ganglion are known as preganglionic nerve fibers. All preganglionic fibers, whether they are in the sympathetic nervous system, sympathetic d ...

nerve fibers originate in the inferior salivatory nucleus of the rostral medulla and travel anteriorly and laterally to exit the brainstem between the medullary olive and the

with the other components of CN IX. Note: These neurons do not form a distinct nucleus visible on cross-section of the brainstem. The position indicated on the diagram is representative of the location of the cell bodies of these fibers. Intracranial course Upon emerging from the lateral aspect of the medulla, the visceral motor fibers join the other components of CN IX to enter the

. Within the jugular foramen, there are two glossopharyngeal ganglia that contain nerve cell bodies that mediate general, visceral, and special sensation. The visceral motor fibers pass through both ganglia without synapsing and exit the inferior ganglion with CN IX general sensory fibers as the

. Before exiting the jugular foramen, the tympanic nerve enters the

petrous portion of the temporal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three a ...

and ascends via the inferior tympanic canaliculus to the

tympanic cavity The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external audit ...

. Within the tympanic cavity the tympanic nerve forms a plexus on the surface of the promontory of the middle ear to provide general sensation. The visceral motor fibers pass through this plexus and merge to become the lesser petrosal nerve. The lesser petrosal nerve re-enters and travels through the temporal bone to emerge in the

middle cranial fossa The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull ...

just lateral to the greater petrosal nerve. It then proceeds anteriorly to exit the skull via the foramen ovale along with the

mandibular nerve In neuroanatomy, the mandibular nerve (V) is the largest of the three divisions of the trigeminal nerve, the fifth Cranial nerves, cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which ...

component of CN V (V3). Extra-cranial course and final innervations Upon exiting the skull, the lesser petrosal nerve synapses in the

otic ganglion The otic ganglion is a small parasympathetic ganglion located immediately below the foramen ovale in the infratemporal fossa and on the medial surface of the mandibular nerve. It is functionally associated with the glossopharyngeal nerve and i ...

, which is suspended from the

immediately below the foramen ovale. Postganglionic fibers from the otic ganglion travel with the auriculotemporal branch of CN V3 to enter the substance of the

. Hypothalamic Influence Fibers from the

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

and

olfactory system The olfactory system, is the sensory nervous system, sensory system used for the sense of smell (olfaction). Olfaction is one of the special senses directly associated with specific organs. Most mammals and reptiles have a main olfactory system ...

project via the

dorsal longitudinal fasciculus The dorsal longitudinal fasciculus (DLF) is a distinctive nerve tract in the midbrain. It extends from the hypothalamus rostrally to the spinal cord caudally, and contains both descending and ascending fibers. Descending fibers arise in the hyp ...

to influence the output of the inferior salivatory nucleus. Examples include: 1) dry mouth in response to fear (mediated by the hypothalamus); 2) salivation in response to smelling food (mediated by the olfactory system)

Overview of visceral sensory component

This component of CN IX innervates the baroreceptors of the

and chemoreceptors of the carotid body. ;Peripheral and intracranial course. :Sensory fibers arise from the

and carotid body at the common carotid artery bifurcation, ascend in the carotid sinus nerve, and join the other components of CN IX at the inferior glossopharyngeal ganglion. The cell bodies of these neurons reside in the inferior glossopharyngeal ganglion. The central processes of these neurons enter the skull via the

. ;Central course – visceral sensory component :Once inside the skull, the visceral sensory fibers enter the lateral medulla between the olive and the

and descend in the solitary tract to synapse in the caudal solitary nucleus. From the solitary nucleus, connections are made with several areas in the reticular formation and

to mediate cardiovascular and respiratory reflex responses to changes in blood pressure, and serum concentrations of CO2 and O2. Clinical correlation The visceral sensory fibers of CN IX mediate the afferent limb of the pharyngeal reflex in which touching the back of the pharynx stimulates the patient to gag (i.e., the gag reflex). The efferent signal to the musculature of the pharynx is carried by the branchial motor fibers of the vagus nerve.

Overview of somatic sensory component

This component of CN IX carries general sensory information (pain, temperature, and touch) from the skin of the external ear, internal surface of the tympanic membrane, the walls of the upper pharynx, and the posterior one-third of the tongue, anterior surface of the epiglottis, vallecula. ;Peripheral course :Sensory fibers from the skin of the external ear initially travel with the auricular branch of CN X, while those from the middle ear travel in the tympanic nerve as discussed above (CN IX visceral motor section). General sensory information from the upper pharynx and posterior one-third of the tongue travel via the pharyngeal branches of CN IX. These peripheral processes have their cell body in either the superior or inferior glossopharyngeal ganglion. ;Central course :The central processes of the general sensory neurons exit the glossopharyngeal ganglia and pass through the jugular foramen to enter the brainstem at the level of the medulla. Upon entering the medulla these fibers descend in the spinal trigeminal tract and synapse in the caudal spinal nucleus of the trigeminal.

Overview of special sensory component

The special sensory component of CN IX provides taste sensation from the posterior one-third of the tongue. ;Peripheral course :Special sensory fibers from the posterior one-third of the tongue travel via the pharyngeal branches of CN IX to the inferior glossopharyngeal ganglion where their cell bodies reside. ;Central course – special sensory component :The central processes of these neurons exit the inferior ganglion and pass through the jugular foramen to enter the brainstem at the level of the rostral medulla between the olive and inferior cerebellar peduncle. Upon entering the medulla, these fibers ascend in the tractus solitarius and synapse in the gustatory part of nucleus solitarius. Taste fibers from CN VII and X also ascend and synapse here. Ascending secondary neurons originating in nucleus solitarius project bilaterally to the ventral posteromedial (VPM) nuclei of the thalamus via the central tegmental tract. Tertiary neurons from the thalamus project via the posterior limb of the internal capsule to the inferior one-third of the primary sensory cortex (the gustatory cortex of the parietal lobe).

Associated brainstem nuclei

* Solitary nucleus: taste from the posterior 1/3 of the tongue and information from carotid sinus baroreceptors and carotid body chemoreceptors * Spinal nucleus of the trigeminal nerve: Somatic sensory fibers from the internal surface of the tympanic membrane, middle ear, upper part of the pharynx, soft palate and posterior 1/3 of the tongue *

Nucleus ambiguus The nucleus ambiguus ("ambiguous nucleus" in English) is a group of large motor neurons, situated deep in the medullary part of the reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of neurons that innerva ...

lower motor neuron Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower ...

s for the

muscle * Inferior salivatory nucleus: preganglionic

neurons to the otic ganglion and then to the parotid gland

Functions

* It receives general somatic sensory fibers ( ventral trigeminothalamic tract) from the

tonsils The tonsils ( ) are a set of lymphoid organs facing into the aerodigestive tract, which is known as Waldeyer's tonsillar ring and consists of the adenoid tonsil (or pharyngeal tonsil), two tubal tonsils, two palatine tonsils, and the lingual ...

, the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles (malleus, incus, and stapes), which transfer the vibrations ...

and the posterior 1/3 of the tongue. * It receives special visceral sensory fibers (

) from the posterior 1/3 of the

. * It receives visceral sensory fibers from the carotid bodies,

. * It supplies

fibers to the

via the

. * It supplies motor fibers to

, the only motor component of this cranial nerve. * It contributes to the pharyngeal plexus.

Clinical significance

Damage

Damage to the glossopharyngeal nerve can result in loss of taste sensation to the posterior one third of the tongue, and impaired

swallowing Swallowing, also called deglutition or inglutition in scientific and medical contexts, is a physical process of an animal's digestive tract (e.g. that of a human body) that allows for an ingested substance (typically food) to pass from the mou ...

Examination

The clinical tests used to determine if the glossopharyngeal nerve has been damaged include testing the

gag reflex The pharyngeal reflex or gag reflex is a reflex muscular contraction of the back of the throat, evoked by touching the roof of the mouth, back of the tongue, area around the tonsils, uvula, and back of the throat. It, along with other aerodigest ...

of the mouth, asking the patient to

swallow The swallows, martins, and saw-wings, or Hirundinidae are a family of passerine songbirds found around the world on all continents, including occasionally in Antarctica. Highly adapted to aerial feeding, they have a distinctive appearance. The ...

cough A cough is a sudden expulsion of air through the large breathing passages which can help clear them of fluids, irritants, foreign particles and Microorganism, microbes. As a protective reflex, coughing can be repetitive with the cough reflex fol ...

, and evaluating for speech impediments. The clinician may also test the posterior one-third of the tongue with bitter and sour substances to evaluate for impairment of taste. 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. The gag reflex can also be used to evaluate the glossopharyngeal nerve.

Additional images

File:Brain human normal inferior view with labels en.svg, Inferior view of the human brain, with the cranial nerves labelled. File:Gray567.png, Dura mater and its processes exposed by removing part of the right half of the skull, and the brain. File:Gray719.png, Hind- and mid-brains; postero-lateral view.( File:Gray779.png, Alveolar branches of superior maxillary nerve and sphenopalatine ganglion. File:Gray792.png, Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ. File:Gray794.png, Hypoglossal nerve, cervical plexus, and their branches.

References

Saladin, Anatomy and Physiology: The Unity of Form and Function, 6th edition

External links

* * * * () {{Authority control Cranial nerves Gustatory system Pharynx Otorhinolaryngology Autonomic nervous system Parasympathetic nervous system Human head and neck Nervous system Neurology Nerves of the head and neck