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.
At 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.
The 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).
In 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 lung.
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,
The 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 colon.
Vagus nerve distribution
Dorsal nucleus of vagus (pinkish) in the floor of 4th ventricle of the medulla in PAL-Weigert stain axial section
Electronic School of Medicine
Creator: Oluwole Ogunranti