Vagus nerve

The vagus nerve (n. vagus) innervates the meninges, organs of the neck, chest cavity, most of the abdominal organs. The fibers of the vagus nerve transmit impulses that slow the heartbeat, constrict the bronchi, increase peristalsis and relax the intestinal sphincters, increase the secretion of glands, etc. The vagus nerve contains sensory, motor and secretory fibers. The sensory fibers are the central processes of the pseudounipolar neurons of the superior and inferior ganglia of the vagus nerve. The superior ganglia (ganglion superius) of the vagus nerve is located at the level of the jugular foramen, the inferior ganglia (ganglion inferius) is slightly lower. The motor fibers of the vagus nerve originate from the double nucleus located in the tegmentum of the medulla oblongata. The autonomic preganglionic parasympathetic fibers originate from the posterior nucleus of the vagus nerve. In addition, the vagus nerve contains sympathetic fibers that approach it as part of the connecting branches from the sympathetic trunk.

The vagus nerve emerges from the medulla oblongata with 10-18 roots behind the olive, next to the glossopharyngeal and accessory nerves. The roots of the vagus nerve unite into one trunk, which goes through the anterior part of the jugular foramen. After leaving the foramen, the vagus nerve is initially located behind the glossopharyngeal nerve and in front of the accessory nerve and the internal jugular vein, lateral and in front of the hypoglossal nerve. In the neck, the vagus nerve passes between the internal jugular vein and the internal carotid artery, and below - between the same vein and the common carotid artery. The common carotid artery, vagus nerve and internal jugular vein form a vascular-nerve bundle in the neck, surrounded by a common connective tissue sheath. Then the vagus nerve penetrates the thoracic cavity, into the posterior mediastinum. The right vagus nerve passes in front of the right subclavian artery, the left vagus nerve - in front of the aortic arch. Below, the vagus nerve goes along the back surface of the root of the lung on its side. Further, both nerves are adjacent to the outer surface of the esophagus. The left vagus nerve gradually shifts to the front surface of the esophagus, the right - to its back surface. The vagus nerves together with the esophagus pass through the diaphragm into the abdominal cavity. The left vagus nerve is located on the front wall of the stomach, the right - on the back.

According to the topographic principle, the vagus nerve is divided into the cervical, cervical, thoracic and abdominal sections.

From the head section of the vagus nerve (to the level of the jugular foramen) the meningeal and auricular branches extend:

1. the meningeal branch (r. meningeus) from the superior ganglion of the vagus nerve goes to the dura mater of the brain in the region of the posterior cranial fossa, and then to the occipital and transverse sinuses;
2. The auricular branch (r. auricularis) from the superior ganglion of the vagus nerve passes into the mastoid canal of the temporal bone, innervates the skin of the posterior wall of the external auditory canal and the outer surface of the auricle.

Several branches extend from the cervical spine:

1. pharyngeal branches (rr. pharyngei, s. pharyngealis) in the amount of two or three go to the walls of the pharynx, where together with the branches of the glossopharyngeal nerve and the superior sympathetic ganglion they form the pharyngeal plexus (plexus pharyngeus). The pharyngeal plexus innervates the muscles - constrictors of the pharynx; the muscle that raises the soft palate; the muscle of the uvula (palatine), the palatoglossus and palatopharyngeal muscles. The sensory branches of the pharyngeal plexus innervate the mucous membrane of the pharynx and the root of the tongue, as well as the thyroid and parathyroid glands;
2. The superior cervical cardiac branches (rr. cardiaci cervicales superiors) depart in the amount of one to three from the vagus nerve or from the superior laryngeal nerve, descend down along the common carotid artery. These branches go along the posterior surface of the thyroid gland, then the left branches - along the anterior surface of the aortic arch and are part of the cardiac plexuses. The left superior cervical cardiac branches participate in the formation of the superficial extraorgan cardiac plexus, the right ones enter the deep cardiac plexus. The superior cervical cardiac branches also innervate the thymus and thyroid gland;
3. The superior laryngeal nerve (n. laryngeus superior) departs from the inferior ganglion of the vagus nerve, runs forward along the lateral surface of the pharynx behind the internal and external carotid arteries. At the level of the hyoid bone, the superior laryngeal nerve is divided into external and internal branches. The external branch (r. externus) innervates the inferior constrictor of the pharynx, the cricothyroid muscle, and gives fibers to the thyroid gland. The internal branch (r. internus), sensitive in composition, together with the superior laryngeal artery pierces the thyrohyoid membrane and innervates the mucous membrane of the larynx above the glottis and the mucous membrane of the root of the tongue.
4. The recurrent laryngeal nerve (n. laryngeus reccurens) has different origins on the right and left. The right recurrent laryngeal nerve branches off from the vagus nerve at the level of the subclavian artery, bends around it from below and behind, and ascends along the lateral surface of the trachea. The left recurrent laryngeal nerve begins at the level of the aortic arch, bends around it from below in the anteroposterior direction, and goes up in the groove between the esophagus and trachea. Tracheal branches branch off from the recurrent laryngeal nerves. The terminal branch of the recurrent nerve on each side is the inferior laryngeal nerve (n. laryngeus inferior), which innervates the mucous membrane of the larynx below the glottis and all the muscles of the larynx except the cricothyroid muscle.

In the thoracic region, branches of the vagus nerve extend to the internal organs:

1. thoracic cardiac branches (rr. cardiaci thoracici) are directed to the extraorgan superficial and deep cardiac plexuses;
2. bronchial branches (rr. bronchiales) go to the root of the lung, where, together with the sympathetic nerves, they form the pulmonary plexus (plexus pulmonalis), which surrounds the bronchi, entering the lung with them;
3. The esophageal branches (rr. esophageales) participate in the formation of the esophageal plexus (plexus esophageus) located on the surface of the esophagus, the branches of which go to its walls, muscles and mucous membrane.

The abdominal part of the vagus nerve is represented by the anterior and posterior vagus trunks, emerging from the esophageal plexus, and their branches:

1. the anterior vagal trunk (truncus vagalis anterior) passes from the anterior surface of the esophagus to the anterior wall of the stomach, located along its lesser curvature. From the anterior vagal trunk, the anterior gastric branches (rr. gastricianteriores) and hepatic branches (rr. hepatici) extend to the stomach, which go between the layers of the lesser omentum to the liver;
2. The posterior vagus trunk (truncus vagalis posterior) passes onto the posterior wall of the stomach, located mainly along its lesser curvature. The posterior vagus trunk gives off posterior gastric branches (rr. gastrici posteriores) and celiac branches (rr. coeliaci), which go along the left gastric artery to the celiac plexus.

The fibers of the vagus nerve, together with the sympathetic fibers of the celiac plexus, go to the liver, spleen, pancreas, small and large intestines (to the level of the descending colon).

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