VAGUS NERVE By : Dani mamo

COARSE Nerve takes it origin from the anterolateral surface of upper part of medulla oblongata between the olive and the inferior cerebral peduncle. Then it travels laterally leaving the skull through jugular foramen. Descends vertically in the neck within the carotid sheath.

RIGHT VAGUS NERVE 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 crosses anterior to the right subclavian artery, runs posterior to the superior vena cava, descends posterior to the right main bronchus, and contributes to 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.

LEFT VAGUS NERVE enters the thorax between left common carotid artery and left subclavian artery and descends on 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, breaks up into pulmonary plexus, continues into the esophageal plexus, and enters the abdomen as the anterior vagal trunk in the esophageal hiatus of the diaphragm.

Branches In the jugular foremen, superior ganglion gives: - Auricular nerve - Meningeal nerves Branches arising in neck are: - Pharyngeal nerve - Carotid branches - Superior laryngeal nerve - Cardiac branches - Recurrent laryngeal nerve

- Meningeal branches → dura of posterior cranial fossa - Auricular branches → concha and root of auricle, post half of ext auditory meatus, outer surface of tympanic membrane - Pharyngeal branch → pharyngeal plexus, muscles of pharynx and soft palate (except tensor veli palatini - carotid branches → carotid body and carotid sinus -Superior laryngeal nerve 1)external laryngeal nerve→ cricothyroid, inferior constrictor and pharyngeal plexus 2) internal laryngeal nerve→ mucous membrane of larynx upto vocal cords

- Recurrent laryngeal nerve supplies: 1) All intrinsic muscles of larynx except cricothyroid 2) Sensory below the level of vocal cords 3) Cardiac branches to deep cardiac plexus 4) Branches to trachea and oesophagus 5) To inferior constrictor - Cardiac branches → cardiac plexus

Nuclei The vagus nerve includes axons which emerge from or converge onto four nuclei of the medulla: 1) The dorsal nucleus of vagus nerve — which sends parasympathetic output to the viscera, especially the intestines 2) The nucleus ambigus — which gives rise to the branchial efferent motor fibers of the vagus nerve and preganglionic parasympathetic neurons that innervate the heart 3) The solitary nucleus — which receives afferent taste information and primary afferents from visceral organs 4) The spinal trigeminal nucleus — which receives information about deep/crude touch, pain, and temperature of the outer ear, the dura of the posterior cranial fossa and the mucosa of the larynx

FUNCTION - General visceral efferent (GVE) — provides parasympathetic innervation to glands of mucous membranes of the pharynx, larynx, organs in the neck, thorax, and abdomen. - Special visceral efferent (SVE) — innervates skeletal muscles of the pharynx and larynx. - General somatic afferent (GSA) — carries sensation from the external auditory meatus and tympanic membrane. - General visceral afferent (GVA) — carries information from the thoracic and abdominal viscera; aortic body and arch. - Special visceral afferent (SVA) — carries taste of the epiglottis region of the tongue.

CLINICALS The vagus nerve is tested clinically by comparing the palatal arches on the two sides. On the paralyzed side therr will be no arching and uvula is pulled to normal side. PARALYSES OF X NERVE PRODUCES: 1) Nasal regurgitation of swallowed liquid 2) Nasal twang in voice 3) Hoarseness 4) Flattening of palatal arch 5) Cadaveric position of vocal cord 6) Dysphagia