GLOSSOPHARYNGEAL NERVE

NERVE SUPPLY OF TONSILS

• Lesser palatine branches of sphenopalatine ganglion & Glossopharyngeal N (major supply)
• Glossopharyngeal nerve also gives sensory supply to middle ear.
• Pain from the tonsils can be referred to middle ear along Glossopharyngeal nerve.

Ans. B. Glossopharyngeal nerve

Circumvallate papilla is one of the large papillae near the base on the dorsal aspect of the tongue arranged in a  V-shape. The taste buds are located in the epithelium of the trench surrounding the papilla.

Motor nerve supply of tongue: All the intrinsic and extrinsic muscles of the tongue are supplied by the hypoglossal nerve except the palatoglossus muscle which is supplied by the cranial part of the accessory nerve through the pharyngeal plexus.  

Glossopharyngeal nerve is both general sensory and special sensory to the posterior 1/3rd of the tongue and circumvallate papillae. Posterior most part of the tongue is supplied by the internal laryngeal nerve which is a branch of vagus nerve.

The sensory nerve fibers from the taste buds on the anterior two-thirds of the tongue travel in the chorda tympani branch of the facial nerve and those from the posterior third of the tongue reach the brainstem via the glossopharyngeal nerve. 

The fibers from areas other than the tongue (eg, pharynx) reach the brain stem via the vagus nerve.

On each side, these nerves unite in the gustatory portion of the nucleus of the solitary tract (NTS) in the medulla oblongata.

From there, axons of second-order neurons ascend in the ipsilateral medial lemniscus and project directly to the ventral posteromedial nucleus of the thalamus. 

From the thalamus, the axons of the third-order neurons pass to neurons in the anterior insula and the frontal operculum in the ipsilateral cerebral cortex.

The sensory innervation of the tongue reflects its embryological development.

The nerve of general sensation to the presulcal part is the lingual nerve, which also carries taste sensation derived from the chorda tympani branch of the facial nerve.

The nerve supplying both general and taste sensation to the postsulcal part is the glossopharyngeal nerve.

An additional area in the region of the valleculae is supplied by the internal laryngeal branch of the vagus nerve.

D i.e. Hypobranchial eminence

–   Tongue muscles originate from myoblast of occipital somites. Thus tongue musculature is innervated by hypoglossal nerve.

–  Glossopharyngeal (9th) nerve supplies posterior (1/3) part of tongue because it develops from hypobrachial eminence (copula).

Parathyroid glands develop from 4^th (superior) & 3^rd (inferior para thyroid glands) pharyngeal endodermal pouch.

Ans.D. A i.e,Facial nerve supplies fungiform papillae; B i.e. Glossopharyngeal nerve supplies circumvallate papillae; C i.e. Genioglossus is the safety muscle

Anterior 2/3rd of tongue is supplied by chorda tympani branch of facial nerve (carrying taste sensation) & lingual nerve (carrying general sensation); posterior 1/3rd of tongue is supplied by glossopharyngeal nerve (carrying taste & general sensation both), and posterior-most tongue in the region of valleculae is supplied by internal laryngeal branch of vagus nerve.

The fungiform papillae are club-shaped projections on the tongue, generally red. They are found on the tip of the tongue, scattered amongst the filiform papillae but are mostly present on the tip and sides of the tongue. Circumvallate papillae are located towards the back of the tongue.

Except for palatoglossus (extrinsic muscle), all muscles of the tongue (i.e. all intrinsic muscles eg bilateral superior & inferior longitudinal, transverse & vertical and 3 pairs of extrinsic muscles i.e. genioglossus, hypoglossus & styloglossus/ chondroglossus) are supplied by hypoglossal nerve.

Hypoglossal nerve has only motor (but no sensory) supply to tongue, so injury to it can not lead to loss of taste or general sensation. Injury to hypoglossal nerve present with pure motor tongue features such as ipsilateral muscular dysfunction.

• The nerve supply of middle ear is derived from tympanic plexus which lies over the promontory.
• The inferior ganglion of the glossopharyngeal nerve gives off the tympanic nerve which enters the middle ear through the tympanic canaliculus and takes part in formation of the tympanic plexus on the medial wall of middle ear.
• This distributes it fibres to the middle ear, and also to the auditory tube, aditus ad atrum mastoideum (aditus to mastoid antrum).
• Glossopharyngeal nerve —> Tympanic nerve/tympanic plexus —> Auditory tube

Stylopharyngeus is the only muscle in the pharynx innervated by the glossopharyngeal nerve (CN IX) and is done by its motor branch, which supplies special visceral efferent (SVE) fibers to it.

All other muscles of pharynx are supplied by cranial accessory nerve through branches of vagus.

Glossopharyngeal and lesser palatine nerves supply palatine tonsil

Palatine tonsil

• The Palatine tonsils are two prominent masses situated one on either side between the glossopalatine and pharyngopalatine arches.
• Each tonsil consists fundamentally of an aggregation of lymphoid tissue underlying the mucous membrane between the palatine arches.
• In the child the tonsils are relatively (and frequently absolutely) larger than in the adult
• The follicles of the tonsil are lined by a continuation of the mucous membrane of the pharynx, covered with stratified squamous epithelium

Arteries supplying the tonsil are the:

• Dorsalis linguae from the lingual
• The ascending palatine and tonsillar from the external maxillary
• The ascending pharyngeal from the external carotid
• The descending palatine branch of the internal maxillary
• A twig from the small meningeal.
• The veins end in the tonsillar plexus, on the lateral side of the tonsil
• The nerves are derived from the sphenopalatine ganglion, and from the glossopharyngeal.

The glossopharyngeal nerve, the vagus nerve and the accessory nerve, so cranial nerves IX, X and XI pass through the jugular foramen. That’s four structures to remember. You’ve got cranial nerves IX, X and XI and you’ve got the internal jugularvein.

Ans;D).Glossopharyngeal nerve

Markesd stucture is Jugular Foramen

Glossopharyngeal nerve travel through the middle compartment of the jugular foramen. Jugular foramen is formed by the petrous portion of the temporal and occipital bones.

Jugular Foramen:

1. Anterior part: Inferior Petrosal Sinus

2. Middle part: 

• a. CN IX (Glossopharyngeal nerve)
• b. CN X (Vagus nerve)
• c. CN XI (Accesory nerve)
• d. Meningeal branch of Ascending Pharyngeal Artery

3. Posterior part:

• a. Internal Jugular vein (IJV) – Sigmoid sinus junction
• b. Emissary vein (Sigmoid sinus to occipital vein)
• c. Occipital artery

Ans:D.)Hypobranchial Eminence.

The  structure marked as number  “5” (Red arrow) in the picture above represents the Hypobranchial Eminence.

• The hypopharyngeal eminence or hypobranchial eminence is a midline swelling of the third and fourth pharyngeal arches, in the development of the tongue.
• It appears in the fifth and sixth weeks of embryogenesis.
• The hypopharyngeal eminence forms mostly from the endoderm of the third pharyngeal arch and only partially from the fourth pharyngeal arch.
• It quickly grows to cover the copula formed earlier from the second pharyngeal arch, and will form the posterior one third of the tongue.