The vagus nerve is the tenth cranial nerve, and its name comes from the latin word vagary, which means indefinite or wandering.

This actually reflects its wide distribution seeing as the vagus nerve is the most extensively distributed cranial nerve; in fact, it innervates structures all the way from the head and neck to parts of the digestive tract!

The vagus nerve has multiple functions such as somatic, visceral and special sensory innervation, as well as somatic and visceral motor innervation.

Now, the vagus nerve emerges from the lateral medulla through a group of rootlets that join and leave the cranium through the jugular foramen along with cranial nerves 9 and 11, or the glossopharyngeal and spinal accessory nerves.

Both left and right vagus nerves leave the cranium through the jugular foramen on their respective sides, and penetrate the carotid sheath.

Then, they descend within the carotid sheath, posterior to the common carotid artery and medial to the internal jugular vein. From here, each vagus nerve takes a different course as they enter the thorax.

The right vagus nerve crosses the right subclavian artery anteriorly, runs posterior to the superior vena cava and descends posterior to the right main bronchus to contribute to the cardiac, pulmonary and esophageal plexuses.

When it reaches the lower part of the esophagus, it forms the posterior vagal trunk and then enters the abdomen through the esophageal hiatus of the diaphragm.

The left vagus nerve, on the other hand, enters the thorax between the left common carotid artery and the left subclavian artery and descends on the aortic arch.