GLOSSOPHARYNGEAL NERVE

INTRODUCTION:

• The glossopharyngeal nerve, known as the ninth cranial nerve (CN IX), is a mixed nerve that carries afferent sensory and efferent motor information.

• It exits the brainstem out from the sides of the upper medulla, just rostral (closer to the nose) to the vagus nerve.

• The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, while the sensory division originates from the cranial neural crest.

• It is the nerve of third branchial (pharyngeal) arch.

STRUCTURE:

 Medulla oblongata

        ↓

Glossopharyngeal nerve ( laterally across or below the flocculus) (b/w internal jugular vein & internal artery)

        ↓

Jugular foramen

↓Descends

Beneath the styloid process 

↓Curves forward

Stylopharyngeus and middle pharyngeal constrictor muscle

↓passes under

Hyoglossus muscle

↓supplies

Palatine tonsil, the mucous membrane of the fauces and base of the tongue, and the serous glands of the mouth.

BRANCHES:

• Tympanic nerve (Jacobson’s nerve)

• Branch to Stylopharyngeus

• Tonsillar branch- supply tonsil and soft palate.

• Carotid branch (Nerve of Herring)- for carotid body and  carotid sinus.

• Pharyngeal branches: from pharyngeal plexus with branches of vagus and sympathetic nerves.

• Lingual branches- Supply posterior 1/3 of tongue and circumvallate papillae, carrying both taste and general sensations.

• A communicating branch to the Vagus nerve

FUNCTIONAL COMPONENTS & BRAINSTEM CONNECTIONS:

FUNCTIONAL  COMPONENT	NUCLEUS	DISTRIBUTION	FUNCTION
Special visceral (branchial) efferent	Nucleus ambiguus	Stylopharyngeus
General visceral efferent	Inferior salivatory	Parotid (via otic ganglion)	Parasympathetic  secretomotor to parotid gland.
General  visceral afferent	Nucleus solitarius (lower part)	Carotid sinus Carotid body Oropharynx Soft palate	Control of BP Controls respiration Initiates swallowing reflexes Palatal reflexes
Special visceral afferent	Nucleus solitarius (upper part)	Posterior 1/3 tongue and circumvallate papillae	Taste sensation
General  somatic afferent	Spinal nucleus of V	Middle ear,  tympanic membrane, mastoid antrum auditory tube	Middle ear pain

 FUNCTIONS:

There are a number of functions of the glossopharyngeal nerve:

• It receives general somatic sensory fibers (ventral trigeminothalamic tract) from the tonsils, the pharynx, the middle ear and the posterior 1/3 of the tongue.

• It receives special visceral sensory fibers (taste) from the posterior one-third of the tongue.

• It receives visceral sensory fibers from the carotid bodies, carotid sinus.

• Nerve supply of circumvallate papillae is glossopharyngeal nerve

• 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.

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