Facial nerve
The facial nerve is seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla.Its main function is motor control of most of the facial muscles and muscles of the inner ear. It also supplies parasympathetic fibres to the submandibular gland and sublingual glands via chorda tympani nerve and the submandibular ganglion, and to the lacrimal gland via the pterygopalatine ganglion. In addition, it receives taste sensations from the anterior two-thirds of the tongue. There is also a small amount of cutaneous sensation carried by the nervus intermedius from the skin in and around the auricle (earlobe).
The motor part of the facial nerve arises from the facial nerve nucleus in the pons while the sensory part of the facial nerve arises from the nervus intermedius.
The motor part of the facial nerve enters the petrous temporal bone into the internal acoustic canal (intimately close to the inner ear) then runs a tortuous course (including two tight turns) through the fallopian canal, emerges from the stylomastoid foramen and passes through the parotid gland, where it divides into five major branches.
No other nerve in the body travels such a long distance through a bony canal.
The five main branches of the facial nerve are, from top to bottom:
- temporal branch of the facial nerve
- zygomatic branch of the facial nerve
- buccal branch of the facial nerve
- mandibular branch of the facial nerve
- cervical branch of the facial nerve
Bell's palsy is the result of damage to the facial nerve. This usually happens at the narrowest point of the fallopian canal.
