Tuesday, February 1, 2011

Facial Nerve (CN VII)

The facial nerve is the seventh cranial nerve (CN VII). It is a paired nerve with both motor and sensory functions, providing motor innervation to the muscles of facial expression and sensory information of taste sensations from the anterior two-thirds of the tongue and oral cavity. It also supplies preganglionic parasympathetic fibers to several head and neck ganglia. The CN VII originates in the facial nerve nucleus in the pons while the sensory part of it arises from the nervus intermedius. It emerges from the brainstem between the pons and the medulla.

The motor fibers of the facial nerve innervate all the facial musculature; the principal muscles are the frontalis, orbicularis oculi, buccinator, orbicularis oris, platysma, the posterior belly of the digastric, and the stapedius muscle. The sensory fibers has the following components: 1) taste to the anterior two-thirds of the tongue; 2) secretory and vasomotor fibers to the lacrimal gland, the mucous membranes of the nose and mouth, and the submandibular and sublingual salivary glands; 3) cutaneous sensory impulses from the external auditory meatus and region back of the ear.