Gag reflex should not be used as a clinical exam as there can be a bilateral loss of the gag reflex in a healthy patient. If there is a lesion, the uvula shifts away from the paralyzed side. A patient is often asked to open their mouth and say ‘ah,’ this should cause elevation of the uvula. The vagus nerve is commonly tested clinically in conjugation with the glossopharyngeal nerve because of their apparent effects that are oftentimes reliant upon another. Gastric branches supply the stomach celiac branches (mainly derived from the right vagus nerve) supply the pancreas, spleen, kidneys, adrenals, and small intestine. The left vagus is anterior to the esophagus the right vagus is posterior. Įsophageal branches of the vagus nerve are anterior and posterior and form the esophageal plexus. The vagus nerve gives off anterior and posterior bronchial branches in which the anterior branches are along the anterior lung forming the anterior pulmonary plexus, whereas the posterior branches form the posterior pulmonary plexus. While the vagus nerve is within the carotid sheath, it gives off the superior cardiac nerve and is associated with parasympathetic fibers and travels to the heart. All of the laryngeal musculatures receives supply via the recurrent laryngeal nerve except for the cricothyroid muscle (supplied by the laryngeal nerve). The left recurrent laryngeal nerve then loops around the aortic arch distal to the ligamentum arteriosus and then enters the larynx. The right recurrent laryngeal nerve’s fibers branch from the vagus nerve near the right subclavian artery, traveling superiorly to enter the larynx between the cricopharyngeus muscle and the esophagus. The external portion supplies the cricothyroid muscle, whereas the internal branch supplies the mucosa superior to the glottis. The external portion travels distally with the superior thyroid vessels. The internal laryngeal nerve goes through the thyrohyoid membrane entering the larynx. The superior laryngeal nerve travels between the external and internal carotid arteries the nerve divides into internal and external branches near the level of the hyoid. These fibers form the pharyngeal plexus–branches of this plexus innervate the pharyngeal and palate muscles (except the tensor palatine muscle) the pharyngeal plexus also supplies the innervation to the intercarotid plexus which mediates information from the carotid body. The pharyngeal nerve branches arise from the inferior ganglion of CN X containing both sensory and motor fibers. There are four branches of the vagus nerve within the neck: pharyngeal branches, superior laryngeal nerve, recurrent laryngeal nerve, and the superior cardiac nerve. The left vagus nerve travels anteriorly to the subclavian artery and enters the thoracic cavity wedged between the left common carotid and subclavian arteries it then descends posteriorly to the phrenic nerve and posterior to the left lung, then travels medially towards to the esophagus forming the esophageal plexus with the right vagus nerve. The right vagus nerve travels anteriorly to the subclavian artery and then posterior to the innominate artery it makes its descent into the thoracic cavity by traveling to the right of the trachea, and posterior to the hilum on the right, moving medially to form the esophageal plexus with the left vagus nerve. The vagus nerve continues by traveling inferiorly within the carotid sheath where it is located posterior and lateral to the internal and common carotid arteries, and medial to the internal jugular vein. The inferior ganglion of X provides afferent general visceral fibers to the carotid and aortic bodies the efferent fibers of this nerve travel to the nucleus tractus solitarius the inferior ganglion also provides taste sensation to the pharynx and relays this information to the nucleus tractus solitarius. Superior ganglion of X provides afferent general somatic innervation to the external ear and tympanic membrane. Fibers originating from the dorsal motor nucleus of X are efferent, general visceral (EGV) fibers which provide the involuntary muscle control of organs it innervates (cardiac, pulmonary, esophageal) and innervation to glands throughout the gastrointestinal tract. The nerve fibers from the nucleus ambiguous are efferent, special visceral (ESV) fibers which help to mediate swallowing and phonation. The origin of cell bodies for the vagus nerve originates from the nucleus ambiguous the dorsal motor nucleus of X, superior ganglion of X, and the inferior ganglion of X. There are two ganglia on the vagus nerve (superior and inferior) as it exits the jugular foramen the spinal accessory nerve (CN XI) joins the vagus nerve just distal to the inferior ganglion. The vagus nerve has its origin in the medulla oblongata and exits the skull via the jugular foramen.
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