Vagus nerves

In their descent through the thorax the vagus nerves arc, so to speak, attempting to reach the mid-line at all levels. Thus the right vagus is in contact with the trachea, while the left is held away from that structure by the great arteries that spring from the arch of the aorta. The left nerve crosses the arch deep to the left superior intercostal vein, and the right nerve lies on the trachea deep to the arch of the azygous vein. Each vagus passes down behind the lung root, here giving off a large contribution to the pulmonary plexuses. The nerves now pass onwards to achieve their object of reaching the mid-line by entering into the esophageal plexus on the posterior surface of the lower esophagus. In the plexus they become mixed, and the right and left vagal trunks, as they leave the plexus, contain fibers from each vagus. On the arch of the aorta the left vagus nerve flattens out and gives off its recurrent laryngeal branch. This nerve hooks around the ligamentum arteriosum, and, passing up on the right side of the aortic arch, ascends in the groove between trachea and esophagus. The right recurrent laryngeal nerve is given off in the root of the neck and hooks around the right subclavian artery. From the right vagus nerve thoracic cardiac branches enter the deep cardiac plexus. Cardiac branches are given off from each recurrent laryngeal nerve; they join the deep cardiac plexus. The recurrent laryngeal nerves supply the whole trachea and the adjacent esophagus (i.e. above the lung roots) but are of supreme importance because of their supply to muscles of the larynx