ORIGIN: Floor of the 4th
ventricle in the upper medulla.
COURSE/DISTRIBUTION: This is the longest nerve in
the human body extending from the medulla to the junction between the distal 1/3
and proximal 2/3 of the transverse colon. It starts its extrabulbar journey as
rootlets, which pass in the interval between the olive and the inferior
cerebellar peduncle, below the rootlets of the glossopharyngeal nerve and behind
those of the hypoglossal nerve. The rootlets join together to form single nerve,
which traverses the jugular foramen. It enters the foramen below the glossopharyngeal nerve and above the accessory nerve. It enters with the
accessory nerve, the transverse slit of the middle compartment of that foramen
where it lies medial to the accessory nerve before it perforates the arachnoid
and dura mater, to become extracranial. Its extracranial course differs from the
right and left nerves. But its ganglia are placed just below the jugular foramen
and they are two.
small superior ganglion (also called jugular ganglion), which contains cell
bodies for the relatively unimportant somatic fibers coming from the
meningeal and auricular peripheral fibers.
large inferior ganglion called the ganglion nodosum, which has cell bodies
for pseudounipolar sensory neurons associated with the vagus. They include
fibers which mediate taste from the epiglottis, and fibers for general
sensation in the epiglottal, hypopharyngeal, and other thoracic viscera.
the formation of the inferior ganglion, the cranial accessory nerve gives its
contained nucleus ambiguus fibers to the vagus nerve, which then distributes
them to the recurrent laryngeal nerve.
vagus nerve continues its journey on both sides in the carotid sheath lying on
the side of the internal carotid artery, between the artery and the internal
jugular vein and later on the
common carotid artery. It ends at the root of the neck where it passes in front
of the subclavian artery in order to enter the mediastinum. Its cervical (neck)
braches are numerous (see below).
the thorax, the vagus nerve descends in front of the subclavian artery to enter
the thorax. Each vagus nerve (right or left) is attempting to reach the midline
as it courses down the mediastinum. The left vagus crosses in front of the arch
of the aorta deep to the left superior intercostal vein, as it gives off its
recurrent laryngeal nerve, which hooks around the ligamentum arteriosum. It then
passes behind the root of the left lung to reach the midline and form the
esophageal plexus around the esophagus in the posterior mediastinum. It gives a
large contribution to the pulmonary plexus as it passes behind the root of the
right vagus nerve is initially in contact with the trachea. It then passes
behind the right lung root and gives its pulmonary branch to the pulmonary
plexus around the root. It reaches the esophageal plexus around the esophagus
where the left and the right vagi mix to produce two vagal trunks,
vagal trunk (left vagus)
vagal trunk (right vagus).
anterior vagal trunk enters the abdomen via the esophageal opening at the level
of T10, in front of the esophagus. It then gives a cardiac branch to the cardia
of the stomach before dividing into three terminal branches. The posterior vagus
also enters the abdomen via the esophageal opening, behind the esophagus. It
ends in the celiac plexus where its branches reach the whole of the alimentary
tract up to the junction between the distal 1/3 and proximal 2/3 of transverse
recurrent laryngeal nerve
recurrent laryngeal nerve
GSA fibers are pseudounipolar
neurons whose peripheral fibers connect with auricular and meningeal nerves,
which have somatic sensory nerves
GVA fibers are pseudounipolar
neurons for general sensation in the carotid body and in the thoracic
viscera, such as the lungs, trachea and esophagus. The carotid body is provided with end receptors such as baroreceptors and chemoreceptors.
General sensation of the rest of the vagal area (abdomen) is from the
GVE parasympathetic fibers, which
arise from the caudal aspect of the inferior
salivatory nucleus in the floor of the 4th ventricle at
the vagal trigone of the upper medulla. These fibers are for secretomotor
functions in the areas supplied by the vagus nerve- e.g. secretion of
hydrochloric acid in the stomach or enzymes in the whole of the
gastrointestinal tract up to the transverse colon.
But other GVE fibers are associated with smooth muscle function. They
assist the contraction of smooth muscles in the alimentary tract and the
bronchial tree. They also assist the contraction of the heart and their
nucleus is in the dorsal nucleus of vagus at the vagal trigone.
SVE fibers are from the nucleus
ambiguus. They supply the muscles of the 4th and 6th
arches as follows- intrinsic muscles of the pharynx and those of the larynx
(excluding the cricothyroid).
SVA fibers, which mediate taste
from the epiglottis. Their cell bodies lie in the nodosal ganglion and the
central processes relay in the nucleus of the tractus solitarius in the
fibers have two roots- dorsal nucleus of vagus and the inferior salivatory
nucleus - all in the vagal trigone of the rhomboid fossa. Also motor fibers
for the muscles derived from the 4th and 6th arches
are from the caudal extreme of nucleus ambiguus.
fibers are from the nucleus of spinal tract of V (auricular and meningeal),
nucleus of tractus solitarius (taste for epiglottis) and general sensation
(for thoracic viscera and the carotid body) all associated with the floor of
4th ventricle in the vagal trigone.
Electronic School of Medicine
Creator: Oluwole Ogunranti