Neuroanatomy of the Vagus Nerve, the most important human nerve. 2020 [EN🇬🇧] Feat. NESA WORLD®

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The vagus nerve is the X cranial nerve, it is a sensory-motor nerve that includes the neck region, the thorax and the abdomen. It arises from sensory, vegetative and motor fibers of the posterolateral sulcus of the bulb. It leaves the cranial cavity to enter the thorax, where they send their terminal branches to the different viscera.

ORIGIN: brainstem medulla oblongata

COURSE: runs laterally from the brainstem to the jugular foramen. It passes through the jugular foramen and emerges below the skull, just behind the internal jugular vein and internal carotid artery. It passes down the carotid sheath, posterior to the internal jugular vein and internal carotid artery to the root of the neck, and then to the sides of the trachea and esophagus, continuing to the abdomen.

BRANCHES: superior and recurrent laryngeal nerves, meningeal, atrial, pharyngeal, laryngeal, carotid, superior cervical and inferior cardiac, tracheal, bronchial, esophageal, gastric, celiac and hepatic branches. It contributes to the pharyngeal, carotid, cardiac, pulmonary and abdominal plexuses.

INNERVATION: sensory, motor and parasympathetic. The vagus nerve is a mixed nerve. Parasympathetic: motor visceral innervation of the mucous linings of the intestinal tube and viscera from approximately the fauces (throat) to the splenic flexure of the large intestine. Motor: muscle of the palate, pharynx, and larynx except for the tensor vellus palatine and stylopharyngeus muscles. Sensory: general sensation of portions of the outer ear, baro (pressure) and chemoreceptors in the aortic arch, and taste sensations of the epiglottic region.

COURSE: The vagus nerve originates from the medulla oblongata of the brain. The specific nuclei of the brainstem that give rise to the motor fibers of the vagus nerve are the nucleus ambiguus and the dorsal vagal nucleus. The cell bodies of the fibers of the sensory vagus nerve are found in the inferior and superior ganglion and send axons to the nucleus of the brainstem of the solitary tract and to the spinal nucleus of the trigeminal nerve.The vagus nerve exits the medulla laterally, just behind the pontomedullary junction. From here, it runs laterally through the jugular foramen to exit the skull. After exiting the skull, the vagus nerve is located medial to the styloid process. It runs to the root of the posterior neck and between the internal jugular vein and the internal carotid and common carotid arteries. At the root of the neck, the course of the left and right vagus nerve begins to differ.

The first and second branches of the vagus nerve, the meningeal and atrial branches, emerge from the vagus nerve before it leaves the skull. On the outside of the skull, a series of pharyngeal branches emerge that travel to the laryngopharynx. A carotid branch also emerges that contributes to the innervation of the carotid sinus, together with the glossopharyngeal nerve and the cervical sympathetic trunk. The superior laryngeal nerve emerges from the vagus nerve in the neck. The right and left asymmetric recurrent laryngeal nerves ascend from the brachiocephalic artery and aortic arch, respectively, to the larynx. Recurrent laryngeal nerves also emit branches that travel to the cardiac plexuses. The upper and lower cervical cardiac nerves emerge from the vagus nerve in the cervical region and travel down to the cardiac plexus. Below the level at which the recurrent laryngeal nerves branch, the vagus nerve continues downward, emitting thoracic cardiac branches to the cardiac plexuses. In addition to the cardiac branches, the vagus nerve branches travel to the pulmonary plexuses to serve the lungs. As the rest of the vagus nerve reaches the esophagus, it extends into the esophageal plexus, rotating from the left and right sides to the front and back of the esophagus, respectively. These are the anterior and posterior vagal trunks that run through the esophagus to the esophageal hiatus and abdomen. In the abdomen, the vagus nerve forms gastric, hepatic, celiac, and mesenteric branches to innervate the abdominal viscera. (Snell, 2010; Standring 2016)

Summary of the vagus nerve is extensive:

-Conducts the sensitivity of the skin of the ear, retro auricular zone and a portion of the external auditory canal.
- Proprioceptive sensitivity of the mucous membranes of the larynx and larynx, thus protecting the airways.
-Innervates the lower middle constrictor muscles of the pharynx, innervates the soft palate.
-Inervates sensitively the lung, supramesocolic digestive viscera, small intestine, heart and part of the large intestine.
-A motor level innervates the smooth muscles of the lungs, esophagus, most of the intestine, gastric and biliary secretion, respiration, slows down the heart rate.
-Innervates the carotid sinus and controls blood pressure.