Glossopharyngeal and Vagus nerves

Glossopharyngeal and Vagus nerves

Glossopharyngeal (1X) Cranial nerve

• It is principally a Sensory nerve with preganglionic parasympathetic and few motor fibers.

• It has no real nucleus to itself. Instead it shares nuclei with VII and X.

Origin: from the

brain stem (medulla) by 3 nuclei ;

1)Sensory:( solitary nucleus)

2)Motor:(nucleus ambiguus )

in medulla SVE&

3)Parasympathetic (inferior salivary nucleus)

Components of fibers & Deep origin

• SVE fibers: originate from nucleus ambiguus (NA), and supply stylopharyngeus muscle.

• GVE fibers: arise from inferior salivatory nucleus (ISN), relay in otic ganglion, the postganglionic fibers supply parotid gland.

• SVA fibers: arise from the cells of inferior ganglion, their central processes terminate in nucleus of solitary tract (NST), the peripheral processes carries taste from the taste buds on posterior third of tongue.

• GVA fibers: visceral sensation from mucosa of posterior third of tongue, pharynx, auditory tube and tympanic cavity, carotid sinus, end in nucleus of solitary tract (NST).

NST

NA

ISN

Otic G

The glossopharyngeal nerve has two peripheral ganglia. The superior ganglion lies in the jugular foramen and contains the cell bodies of neurons that convey somatosensory information terminating centrally in the spinal trigeminal nucleus. The inferior or petrosal ganglion, which is extracranial, contains the soma of visceral afferent fibers that terminate centrally in the nucleus of the solitary tract.

Course• It arises from the ventral

aspect of the medulla, in groove between the olive and the inferior cerebellar peduncle.

• It leaves the cranial cavity by passing through the jugular foramen together with the Vagus , Acessory nerves and the Internal jugular vein.

- Descends between (internal Carotid Artery & internal jugular Vein)

Then it curves forwards with the stylopharyngeus Muscle between (internal Carotid Artery& external Carotid Artery).

COURSE• Lies Deep to Styloid

process.• Passes between external

and internal carotid arteries at the posterior border of Stylopharyngeus then lateral to it.

• It reaches the pharynx by passing between middle and inferior constrictor, deep to Hyoglossus, where it breaks into terminal branches.

• 1. Motor branch; for one muscle (stylopharyngeus muscle)

• 2. Parasympathetic branch; for parotid gland

• 3. Sensory branches:

A- Pharyngeal br; for mucosa of oropharynx.

B- Lingual br; for the general sensation and taste of the posterior 1/3 of tongue.

C- Tonsillar branch; for palatine tonsil and soft palate

D- Carotid br; from the carotid sinus and body ( pressoreceptors and chemoreceptors).

E-Tympanic: relays in the otic ganglion and gives secretomotor to the parotid gland ( Lesser Petrosal Nerve)

Branches

Lesser Petrosal

Vagus (X) Cranial Nerve

• It is a Mixed nerve. • It is the longest and most

widely distributed cranial nerve.

• It is distributed till the right 2/3 of the transverse colon.

• It contains: • Afferent, Motor , and

Parasympathetic fibers.

Superficial attachment & Course• Origin : arises from the medulla

• Type : motor, sensory , parasympathetic• Leaves the skull through jugular

foramen.• It occupies the posterior aspect of the

carotid sheath between the internal jugular vein laterally and the internal and common carotid arteries medially.

It has two ganglia: Superior ganglion in the jugular

foramen Inferior ganglion, just below the

jugular foramen

CourseIn the neck : descends inside

the carotid sheath between internal jugular vein and internal carotid artery (above) and bet. I.J.V. AND C.C.A. (below )

In the thorax : descends on the side of the trachea, then behind the bronchus, then along the esophagus

In the adomen :the Rt. Vagus runs behind the stomach, and the Lt. Vagus runs infront of the stomach

Components of fibers & Deep origin

• GVE fibers: originate from Dorsal Nucleus of Vagus synapses in parasympathetic ganglia, short postganglionic fibers innervate cardiac muscle, smooth muscles and glands of viscera.

• SVE fibers: originate from Nucleus Ambiguus, to muscles of pharynx and larynx.

• GVA fibers: carry impulse from viscera in neck, thoracic and abdominal cavities to Nucleus of Solitary Tract.

• SVA fibers: sensation from auricle, external acoustic meatus and cerebral dura matter, to Spinal Tract & Nucleus of Trigeminal.

1-Meningeal : to the dura 2-Auricular nerve: to the external acoustic meatus and tympanic membrane. 3-Pharyngeal :to muscles and mucous membrane of the pharynx.4-To carotid body5-Superior Laryngeal: It divides into:(1) Internal Laryngeal : Supplies; the mucous membrane of the larynx as far as the vocal folds. (2) External Laryngeal :supplies the cricothyroid muscle.6-Recurrent Laryngeal : supplies all the muscles of the larynx (except cricothyroid).The mucous membrane below the vocal folds.The mucous membrane of the upper part of trachea.7-Cardiac.

Branches

• Recurrent laryngeal nerve . On the right side, the nerve hooks

around the first part of the subclavian artery and then ascends in the groove between the trachea and the esophagus.

On the left side, the nerve hooks around the arch of the aorta and then ascends into the neck between the trachea and the esophagus.

The nerve is closely related to the inferior thyroid artery,

it supplies all the muscles of the larynx, except the

cricothyroid m. the mucous membrane of the larynx

below the vocal cords the mucous membrane of the upper

part of the trachea.

Cardiac branches (two or three) arise in the

neck, descend into the thorax, and end in the cardiac plexus .

In the thorax :LT. recurrent laryngeal n.,

cardiac branches, pulmonary and oesophageal branches

In the abdomenParasympathetic fibres to

the GIT down to the Rt. 2/3 of the transverse colon

How you can test the Glossopharyngeal & Vagus nerves?

–The person is asked to swallow. –The person is asked to say ‘ah-h-h’ to

check the movements of palate and uvula.

–The ‘gag reflex’ is tested by touching the back of the throat by the tongue depressor.

–The person is asked to speak to check the voice for hoarsness.

Glossopharyngeal nerve lesion characterized by : dysphonia, dysphagia and absence of the gag reflex. Vagus nerve damage: causes hoarseness or loss of voice, impaired swallowing, GI dysfunction, blood pressure anomalies (with IX), If both nerves are affected, it would be fatal.