vagus

The vagus, or vagus nerve, is the tenth cranial nerve (CN X) and a major component of the parasympathetic nervous system. Its name derives from the Latin vagus, meaning wandering, reflecting its long and extensive course through the neck, thorax, and abdomen. It is a mixed nerve, carrying motor, sensory, and autonomic fibers.

Anatomy and course: The vagus roots arise from the medulla oblongata and exit the skull via the jugular foramen. In the neck it runs within the carotid sheath, giving branches to the pharynx and larynx, as well as cardiac and bronchial fibers. It continues posterior to the root of the lung and forms the anterior and posterior vagal trunks in the esophageal plexus, which supply most of the foregut and midgut up to the proximal two-thirds of the transverse colon.

Functions: The vagus provides parasympathetic innervation to the heart, lungs, and much of the gastrointestinal tract, reducing heart rate, constricting bronchi, and promoting digestion through motility and secretions. It supplies motor fibers to muscles of the soft palate, pharynx, and intrinsic muscles of the vocal cords via the pharyngeal and laryngeal branches. Sensory and visceral afferents convey information about organ status; it also mediates taste sensations from the epiglottis and adjacent areas via branches of the superior laryngeal nerve.

Clinical relevance: Vagus nerve injury can cause hoarseness, dysphagia, or bradycardia. Vagotomy has historically reduced acid production in peptic ulcer disease, and modern vagus nerve stimulation is used for epilepsy and treatment-resistant depression. The nerve also plays a key role in autonomic regulation and neuroimmune interactions.