Embryology II. Osteology III. Syndesmology IV. Myology V. Angiology VI.
5g. The Facial Nerve
The facial seventh cranial nerve arises from the pontomedullary junction by two roots: 1 the motor root conveying fibers to muscles derived from second branchial arch mesoderm and 2 the nervus intermedius conveying visceral sensory fibers from the tongue and palate, and preganglionic parasympathetic fibers to the pterygopalatine and submandibular ganglia. The roots pass into the internal acoustic meatus where they join. At the lateral end of the meatus, the facial nerve passes into the facial canal. The nerve then turns sharply posteriorly at the geniculum. The geniculate sensory ganglion is situated here, and the greater petrosal nerve to the pterygopalatine ganglion arises from this region. The facial canal continues posteriorly on the medial wall of the tympanic cavity, passing above the fenestra vestibuli and arching downward and laterally to emerge at the stylomastoid foramen just after giving off the chorda tympani nerve. The posterior auricular nerve and the nerves to the stylohoid and posterior digastric muscles arise before the facial nerve enters the substance of the parotid gland. In the gland, the nerve divides into five groups of branches temporal, zygomatic, buccal, mandibular, and cervical that supply the muscles of facial expression.
In this article, we shall look at the anatomical course of the nerve, and the motor, sensory and parasympathetic functions of its terminal branches. The course of the facial nerve is very complex. There are many branches, which transmit a combination of sensory, motor and parasympathetic fibres.
NCBI Bookshelf. Dominika Dulak ; Imama A. Authors Dominika Dulak 1 ; Imama A. Naqvi 2. It arises from the brain stem and extends posteriorly to the abducens nerve and anteriorly to the vestibulocochlear nerve. It courses through the facial canal in the temporal bone and exits through the stylomastoid foramen after which it divides into terminal branches at the posterior edge of the parotid gland. The facial nerve provides motor innervation of facial muscles that are responsible for facial expression, parasympathetic innervation of the glands of the oral cavity and the lacrimal gland, and sensory innervation of the anterior two-thirds of the tongue. The facial nerve carries both motor and sensory fibers.