Both sensory & Motor Root
FUNCTIONAL COMPONENTS
Special Visceral Efferent fibers arise in the nucleus ambiguus and supply the muscles of pharynx and larynx.
General Visceral Efferent fibers arise in the dorsal motor nucleus of the vagus. These are pre ganglionic parasympathetic fibers. They are distributed to the abdominal and thoracic viscera.
General Visceral Afferent fibers are peripheral processes of the cells located in the inferior ganglion of the nerve. They bring sensations from the pharynx, larynx, trachea, esophagus, and from abdominal and thoracic viscera. These are conveyed by central processes of ganglionic cells to the nucleus of solitary tract
Special Visceral Afferent fibers are also processes of neurons in the inferior ganglion. They carry sensations of taste from the posterior most part of the tongue and the epiglottis. The central processes of the cells terminate in the upper part of nucleus of solitary tract
General Somatic Afferent Fibers are the peripheral process of neurons in the superior ganglion and are distributed to the skin of the external ear. The central processes of the ganglion cells terminate in relation to the spinal nucleus of the trigeminal nerve.
Origin:
Originates from Medulla Oblongata (ant part) b/w olive and Inferior Cerebellar peduncle.
Attach by 8-10 rootlets.
Leaves the skull through the Jugular foramen (middle part) along with the 9th & 11th CN.
Two Sensory Ganglia; Superior ganglion on the nerve within the Jugular foramen; Inferior ganglion just below the foramen.
Below the Inferior ganglion the cranial part of accessory nerve joins the vagus nerve & is distributed mainly in its pharyngeal & recurrent laryngeal branches.
Vagus nerve passes vertically down within the neck in the carotid sheath b/w IJV & ICA & later b/w IJV & CCA at the Root of the neck; lies anterior to the first part of Subclavian artery.
RIGHT VAGUS
Descends to thorax (Lateral to Brachycephalic artery,lateral to trachea),passes behind root of lung,assists the formation of Pulmonary plexus, leaves plexus moves to posterior surface of esophagus, forms esophageal plexus, through the esophageal opening of the diaphragm moves to posterior surface of the stomach
LEFT VAGUS
Descends to thorax, enters thorax between left Common carotid artery and subclavian artery, cross left side of the aortic arch, turns backward behind root of the lung, assists the formation of pulmonary plexus, leaves the plexus, moves to anterior surface of esophagus forms esophageal plexus, through the esophageal opening of the diaphragm moves to anterior surface of the stomach.
BRANCHES OF VAGUS
MENINGEAL BRANCH
Supply Dura matter in Post Cranial Fossa
AURICULAR BRANCH:
Supply
· Medial Surface of auricle
· Floor of External auditory meatus
· Adjacent part of tympanic membrane.
PHARYNGEAL BRANCH:
Contains motor fibers from Cranial part of accessory nerve .
Passes forward between External Carotid Artery & ICA to reach Pharyngeal wall, joins the branches from Glossopharyngeal nerve and sympathetic trunk to form pharyngeal plexus.
Supply
· All the muscles of pharynx EXCEPT Stylopharyngeus (Glossopharyngeal )
· All muscles of soft palate except Tensor veli Palatini (mandibular div of trigeminal nerve)
·
SUPERIOR LARYNGEAL BRANCH:
Divides into
· External Laryngeal
· Internal Laryngeal
External Laryngeal:
Lies close to Superior Thyroid artery
Supply Cricothyroid muscle
Internal Laryngeal:
Sensory to the mucous membrane of piriform fossa and larynx as far down as the vocal cords
RECURRENT LARYNGEAL NERVE
Right Side:
Hooks around 1st part of Subclavian artery & descends in the groove between trachea & esophagus
Left Side:
Hooks around the arch of aorta and descends between trachea and esophagus. Closely related to Inferior thyroid artery
Motor Supply
All the muscles of larynx except cricothyroid
Sensory supply
Mucous membrane of larynx below the vocal folds and mucous membrane of upper part of trachea
CARDIAC BRANCHES
Arise in the neck descend to thorax end in cardiac plexus
Vagus supply thorax, heart, trachea, bronchi, lungs, esophagus with parasympathetic and sensory nerve fibers
CLINICAL CORRELATES:
The vagus nerve is tested clinically by comparing the palatal arches on the two sides. On the paralyzed side there is no arching and uvula is pulled to the normal side.
DAMAGE TO EXTERNAL LARYNGEAL NERVE
Causes some weakness of phonation due to loss of the tightening effect of the cricothyroid on the vocal cord.
RECURRENT LARYNGEAL NERVE
When both recurrent laryngeal nerves are interrupted the vocal cords lie in cadeveric position and phonation is completely lost. Breathing also becomes difficult through the partially opened glottis.
PARALYSIS OF VAGUS NERVE
It produces nasal regurgitation of swallowed liquids; nasal twang in voice; hoarseness of voice; flattening of the palatal arch; cadeveric position of the vocal cords; dysphasia.
IRRITATION OF THE AURICULAR BRANCH OF VAGUS
In the external ear may reflexly cause persistent cough (ear cough), vomiting or even death due to sudden cardiac inhibition
STIMULATION OF THE AURICULAR BRANCH may reflexly produce increase appetite.
IRRITATION OF THE RECURRENT LARYNGEAL NERVE by enlarged lymph node in children may also produce a persistent cough
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