These branches are responsible for innervating the muscles of facial expression. Motor Functions Branches of the facial nerve are responsible for innervating many of the muscles of the head and neck. All these muscles are derivatives of the second pharyngeal arch. The first motor branch arises within the facial canal; the nerve to stapedius. It is responsible for raising the hyoid bone.
It innervates all superficial muscles of the face and scalp, the contraction of which is responsible for all our numerous facial expressions like anger, pain, fear, smile, etc. Facial disfigurement resulting from facial nerve disorders can affect the physical, psychological, and emotional integrity of an individual. This might result in social, occupational, and educational handicap. The facial nerve is one of the most common cranial nerves implicated by disorders. It is a mixed nerve, which carries motor, sensory, and parasympathetic fibers. The motor fiber-innervated muscles developed from second branchial arch, the sensory fibers transmit the special sense of taste, and the parasympathetic fibers supply the submandibular, sublingual, and lacrimal glands [ 1 ].
The labyrinthine segment is the shortest only measuring mm. It is also the narrowest and the most susceptible to vascular compromise see blood supply below. Tympanic segment As the nerve passes posteriorly from the geniculate ganglion it becomes the tympanic segment mm in length and is immediately beneath the lateral semicircular canal in the medial wall of the middle ear cavity. The nerve passes posterior to the cochleariform process , tensor tympani and oval window. Just distal to the pyramidal eminence the nerve makes a second turn posterior or second genu passing vertically downwards as the mastoid segment.
Intra operatively the facial nerve is recognized at 3 constant landmarks:[ citation needed ] At the tip of tragal cartilage where the nerve is 1 cm deep and inferior At the posterior belly of digastric by tracing this backwards to the tympanic plate the nerve can be found between these two structures By locating the posterior facial vein at the inferior aspect of the gland where the marginal branch would be seen crossing it. The cell bodies for the afferent nerves are found in the geniculate ganglion for taste sensation. The cell bodies for muscular efferent nerves are found in the facial motor nucleus whereas the cell bodies for the parasympathetic efferent nerves are found in the superior salivatory nucleus. Development[ edit ] The facial nerve is developmentally derived from the second pharyngeal arch , or branchial arch. The second arch is called the hyoid arch because it contributes to the formation of the lesser horn and upper body of the hyoid bone the rest of the hyoid is formed by the third arch.