Saturday, 23rd June 2018
23 June 2018
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Tenth Cranial Nerve – Anatomy

Tenth Cranial Nerve – Anatomy

 

Tenth Cranial Nerve

Vagus Nerve

Vagus nerve is the tenth cranial nerve. It is so called because of its extensive course, throgh the head, the neck, the thorax and the abdomen. The fibers of the cranial root of the accessory nerves are also distributed through it.

The vagus nerve bears two ganglia, superior and inferior. The superior ganglion is rounded and lies in the jugular foramen.The inferior ganglion is cylindrical and lies near the base of the skull.

Functional Components

Special visceral efferent fibers arise in the nucleus ambiguus and supply the muscles of the palate.Pharynx and larynx.

General visceral efferent fibers arise in the dorsal motor nucleus of the vagus.These are preganglionic parasympathetic fibers. They are distributed to thoracic and abdominal viscera.  The postganglionic neurons are situated in ganglia lying close to the viscera to be supplied.

General visceral afferent fibers are peripheral processes of cells located in the inferior ganglion of the nerve. They bring sensation from the pharynx, larynx, trachea, esophagus and from the abdominal and thoracic viscera.These are conveyed by the central processes of the ganglion cells to the nucleus of the tractus solitarius. Some of these fibers terminate in the dorsal nucleus of the vagus.

Special visceral afferant fibers are also peripheral processes of neurons in the inferior ganglion. They carry sensation of taste from the posterior most part of the tongue and from the epiglottis. The central processes of the cells concerned terminated in the lower part of the nucles of the tract solitaries.

General somatic afferant fibers are peripheral processes 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.

Nuclei

Nucleus ambiguus: Mostly a part of the cranial root of accessory nerve; partly of the vagus.

Dorsal nucleus of vagus: It is a mixed nucleus, being both motor and sensory. Its fibers form the main bulk of the nerve.

The nucleus of tractus solitarius: Distributed through an internal laryngeal nerve to the taste buds of epiglottis and vallecula.

The nucleus of spinal tract of trigeminal.

Course and Relations in Head and Neck

In the intracranial course, fibers run forwards and laterally through the reticular formation of the medulla, between the olivary nucleus and inferior cerebellar peduncle.

The nerve is attached by about ten rootlets, to the posterolateral sulcus of the medulla.

In the intracranial course, the rootlets unite to from a large trunk which passes laterally across the jugular tubercle along with the glossopharyngeal and urinal root of accessory nerves and reaches the jugular foramen.

The nerve leaves the cranial root of the accessory nerve.

Leaving the skull, the nerve descends within the cartoid sheath, in between and posterior to the internal jugular vein and the internal and common carotid arteries.

Read about other nerves

Glossopharyngeal nerve – ninth nerve
Vestibulocochlear nerve – eighth nerve
Facial nerve – seventh nerve

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