Vagus n.

The vagus nerve is the tenth cranial nerve, denoted by CNX (=Cranial Nerve and the roman numeral for 10). The cranial nerves exist as pairs and there are twelve such pairs. The name vagus comes from Latin and means wandering.

The vagus nerves supply parasympathetic (visceral motor) fibers to all of the thoracic and abdominal organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon. The vagus nerves also control a few skeletal muscles in the neck, including muscles of the larynx.

The vagus nerves are responsible for regulating heart rate, constricting the airway, gastrointestinal peristalsis, constriction of the pupils and near focus of the eyes, and movements of the larynx for vocalization (via the recurrent laryngeal nerves) and pharynx for swallowing.

The right vagus nerve crosses anterior to the right subclavian artery and gives rise to the right recurrent laryngeal nerve, which hooks around the right subclavian artery and ascends into the neck between the trachea and esophagus. The right vagus then descends posterior to the superior vena cava and the right main bronchus. It contributes to the cardiac, pulmonary, and esophageal plexuses. It forms the posterior vagal trunk at the lower part of the esophagus and enters the diaphragm through the esophageal hiatus.

The left vagus nerve enters the thorax between left common carotid artery and left subclavian artery and descends anterior to the aortic arch. It gives rise to the left recurrent laryngeal nerve, which hooks around the aortic arch to the left of the ligamentum arteriosum and ascends between the trachea and esophagus. The left vagus further gives off thoracic cardiac branches and breaks up into the pulmonary and esophageal plexuses. It enters the abdomen as the anterior vagal trunk via the esophageal hiatus of the diaphragm.