How does the facial nerve affect facial expression?
The facial nerve passes through the base of the skull in transit from the brain to the muscles that control facial expressions. After leaving the brain, the facial nerve enters the temporal bone through the internal auditory canal, a small bony tube, in very close association with the hearing and balance nerves. Along its inch-and-a-half course through a small canal within the temporal bone, the facial nerve winds around the three middle ear bones, in back of the eardrum, and then through the mastoid (the bony area behind the part of the ear that is visible). After the facial nerve leaves the mastoid, it passes through the salivary or parotid gland and divides into many branches. The facial nerve has four components with several distinct functions: facial expression, taste sensation, skin sensation, and saliva and tear production.
