[Functional anatomy of the glossopharyngeal, vagus, accessory and hypoglossal cranial nerves]

Abstract

The glossopharyngeal nerve and the vagus nerve are mixed nerves containing sensory, gustatory, motor and autonomous fibers (parasympathetic). The glossopharyngeal nerve has mainly visceral afferent fibers from the tongue and pharynx, gustatory fibers from the posterior third of the tongue, parasympathetic afferent fibers from carotid sinus and carotid glomus, parasympathetic efferent fibers for the parotid gland and motor fibers for the muscles of the pharynx. The vagus nerve contains mostly visceral afferent fibers from laryngeal, intrathoracic and abdominal organs, parasympathetic efferent fibers for these intrathoracic and abdominal organs and motor fibers to the pharyngeal and laryngeal muscles. The accessory nerve is divided into two branches, different in their origins and their functions: the cranial portion joins the motor fibers of the vagus nerve, to form the recurrent laryngeal nerve, whereas the spinal portion innervates the sternocleidomastoid muscle and the trapezius muscle. Finally, the hypoglossal nerve is the main motor nerve of the tongue.