Neurology Explained - The Vagus nerve (Cranial Nerve X)
Over the past few days, I have been creating contents on the cranial nerve, and today I will be discussing the 10th cranial nerve. In this post I will be discussing the structure of the vagus nerve, the structures it supplies and the functions of the nerve to its supplied If you missed my previous post, you can read the posts;
Similar to the Cranial Nerve IX, the Vagus nerve has many fibers including the Special visceral Efferent (SVE) fibers, General Somatic Afferent (GSA) Fibers, General Visceral Efferent (GVE), Special visceral Afferent (SVA), and the General Visceral Afferent (GVA) fibers. While other nerves supply the facial region, the Vagus nerve supplies the facial region, the thorax region, and the gastrointestinal tract. It is very important to know that the vagus nerve nuclei originate in the medulla..
In my previous post on cranial nerve 9, I discussed the General Somatic Afferent (GSA) Fibers which are the touch, pain, and temperature fibers that supply the tympanic cavity, the tympanic membrane, and the external acoustic meatus. The General Somatic Afferent fibers from its supplied regions have its axon moving towards the brain, but synapses towards the jugular foramen to form the superior ganglion of cranial nerve 10. The nerve fibres keep moving through the hole of the Jugular foramen from where it goes into the medulla while still giving recurring branches towards the meninges. In the medulla, it moves to the Spinal Nucleus of the Trigeminal Nerve., .
The Special visceral Afferent (SVA) fibers are cranial nerve fibers which are responsible for taste sensation from the tongue to the brain. The nerve moves from the tongue and synapses to the nodose ganglion, and then moves through the jugular foramen into the medulla where it reaches its nuclei origin known as the nucleus of Tractus solitarius..
Special visceral Efferent (SVE) fibers which are motor fibers originate from the nucleus ambigius and pass through the jugular foramen along with the nerve of the cranial nerve 11 motor fiber, and the glossopharyngeal nerve fiber, forming the plexus known as the pharyngeal plexus. The vagus nerve reaches the pharyngeal constrictor muscles of the pharynx, and supplies the palatoglossus muscles, the palatopharyngeal muscle, salpingopharyngeal muscle and the levator veli palatini of the soft pallet as well. The Special Visceral Efferent split to become the superior laryngeal nerve, and the Recurrent laryngeal Nerve. The superior laryngeal nerve supplies the cricothyroid muscle, and the cricopharyngeal muscles. The recurrent laryngeal nerve branches to create the inferior laryngeal nerve which supply the arytenoid muscle.,,.
The General Visceral Afferent (GVA) fibers are also nerves fibers of the vagus nerve. It moves with the superior laryngeal nerve to attach to the stylohyoid membrane, to allow for the picking of visceral sensation in the epiglottis. The fibers also moves with the inferior laryngeal nerve to attach to the larynx mucosa below the vocal cord.. The General Visceral Afferent (GVA) fibers of the Vagus nerve also goes supplies the aortic (arch and bodies), and carotid bodies. The General Visceral Afferent (GVA) fibers move to the synapse to form a nodose ganglion, while the other branch goes into the jugular foramen where it goes into the medulla where they reach its origin nucleus which is the Dorsal Nucleus of Vagus, and the Nucleus of Tractus Solitarius.,.
The General Visceral Efferent fibres move away from the head, giving out the bronchial branch towards the lungs and the bronchi, forming the pulmonary plexus.. It also gives out cardiac branches, which include the thoracic cardiac branch, and the superior cardiac branch which supplies the heart, forming the cardiac plexus which functions in slowing down the heart rate of the heart.. Moving downwards, the GVE fibers form the esophageal plexus which supplies the esophagus allowing it to enable contraction and relation of the esophagus to enable food movement into the stomach.. It moves down to form the posterior gastric nerve and the anterior gastric nerve which helps in churning, mixing, and digestion of the stomach.. The GVE fibers also branch to become the celiac plexus supplies the adrenal glands, the large intestines and small intestine, the kidney, the spleen, and the pancreas . The GVA fibers also supply the lung, the trachea and the bronchi. These fibres are afferent fibers in the lungs serving as irritant receptors.
The Vagus nerve is responsible for innervating the some somatic muscles which cannot be controlled. The vagus nerve is responsible for parasympathetic innervations (autonomic innovation) of muscles of the heart, the kidney, the pancreas, the spleen, and so many more muscles that cannot be controlled. It goes beyond the face and head, it reaches the neck, the thorax, and the abdomen.