Nerve · Neck

Vagus nerve

Nervus vagus

The vagus is the wanderer: the only cranial nerve to leave the head and neck altogether and carry on through the chest into the abdomen. It exits the skull through the jugular foramen, descends the neck inside the carotid sheath between the internal jugular vein and the carotid artery, passes into the thorax, and ends up on the stomach and gut. Along the way it supplies the muscles of the soft palate, pharynx and larynx — so swallowing and the voice depend on it — and it carries the parasympathetic supply to the heart, the airways and the digestive tract as far as the last third of the transverse colon, where it slows the heart, narrows the airways and drives the muscular and secretory work of digestion. Most of its fibres run the other way, though: the vagus is chiefly a sensing nerve, reporting continuously from the aortic arch and the internal organs back to the brainstem. Its branch to the larynx makes an odd detour, hooking under the aortic arch on the left and the subclavian artery on the right before climbing back up the neck.