Hyoid nerve

The hypoglossal nerve (n. hypoglossus), formed by fibers of the motor nucleus, innervates the muscles of the tongue and some muscles of the neck. The nerve exits the brain in the groove between the pyramid and the olive, and is directed forward and laterally into the hypoglossal canal of the occipital bone. After leaving the canal, the hypoglossal nerve goes down and forward, enveloping the vagus nerve and the internal carotid artery from the lateral side. After passing between the internal carotid artery and the internal jugular vein, the nerve is directed under the posterior belly of the digastric muscle and under the stylohyoid muscle into the submandibular triangle, where it forms an arc with its convexity downwards. Then this nerve goes forward and upward into the thickness of the tongue to its muscles.

The descending branch of the hypoglossal nerve extends. It contains motor fibers that join with fibers extending from the anterior branches of the first and second spinal nerves. The resulting cervical loop (ansa cervicalis) is located in front of the common carotid artery or on the anterior surface of the internal jugular vein (less often behind it).

The branches of the cervical loop innervate the omohyoid, sternohyoid, sternothyroid, and thyrohyoid muscles. The hypoglossal nerve contains sensory fibers (from the inferior ganglion of the vagus nerve) that separate in the hypoglossal canal and innervate the dura mater of the brain in the occipital bone region and the occipital sinus.

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