Facial nerve

Introduction

The facial nerve belongs to the cranial nerves. These are a total of twelve nerves that originate in the brain and are responsible for various sensory perceptions, but also for movements. The facial nerve is the seventh of these cranial nerves.

It is responsible both for the movements of the facial muscles and, to a large extent, for the perception of taste. It also carries nerve fibers that supply the glands. Damage to the nerve leads to so-called facial paresis, in which the mimic facial muscles (usually unilateral) can no longer be controlled arbitrarily.

Functions of the facial nerve

Since the facial nerve is composed of different parts, it also fulfils different tasks: The motor fibers that are responsible for movement mainly supply facial muscles that are responsible for facial expression. However, muscles in the neck are also innervated by the facial nerve, as is a small muscle in the ear (Musculus stapedius), which is important for regulating hearing in loud sounds. The sensitive parts, which end in the skin and are responsible for the sensation of touch and pain, supply the skin of the external auditory canal and eardrum.

Other fibres (parasympathetic fibres) are responsible for supplying various glands and end in the oral salivary glands and the lacrimal glands. The function of the glands is regulated by these fibers, preferably their activation with the consequent increased production of saliva secretion. In addition, the facial nerve contains taste fibers (sensory fibers), which enable the perception of taste in the area of the front two thirds of the tongue.

Course of the nerve

The facial nerve originates in the lower, posterior part of the brain, more precisely in the brain stem. Here, its fibers originate from different nuclei located on both sides of the brain. For both halves of the face, there is therefore a facial nerve that supplies one side each.

The nerve runs both inside the skull (intracranial) and outside (extracranial) and leaves the brain in the area of the so-called cerebellar bridge angle. The nerve fibers then run inside the skull through the inner auditory canal and the petrous bone, with many branches already coming off to supply the muscles and glands. Through the Foramen stylomastoideum, a hole in the skull behind the ear, the facial nerve emerges from the skull. It continues through the parotid gland and gives off smaller branches outside the skull to the face and neck muscles.