Facial nerve 215260 225788369 2008-07-15T12:07:13Z 58.165.35.85 /* Outside skull (distal to stylomastoid foramen) */ {{Infobox Nerve | Name = {{PAGENAME}} | Latin = nervus facialis | GraySubject = 202 | GrayPage = 901 | Image = Cranial nerve VII.svg | Caption = Cranial nerve VII | Image2 = Gray790.png | Caption2 = The nerves of the scalp, face, and side of neck. | Width = 300 | Innervates = | BranchFrom = | BranchTo = | MeshName = Facial+Nerve | MeshNumber = A08.800.800.120.250 | DorlandsPre = n_05 | DorlandsSuf = 12565770 | }} The '''facial nerve''' is the seventh (VII) of twelve paired [[cranial nerves]]. It emerges from the brainstem between the [[pons]] and the [[medulla oblongata|medulla]], and controls the muscles of facial expression, and [[taste]] to the anterior two-thirds of the [[tongue]]. It also supplies preganglionic [[parasympathetic]] fibers to several head and neck [[ganglia]]. ==Structure== 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 auditory meatus]] (intimately close to the [[inner ear]]) then runs a tortuous course (including two tight turns) through the [[facial canal]], emerges from the [[stylomastoid foramen]] and passes through the [[parotid gland]], where it divides into five major branches. Though it passes through the parotid gland, it does not innervate the gland. This action is the responsibility of cranial nerve IX, the [[glossopharyngeal nerve]]. Inside one of the tight turns in the facial canal, the facial nerve forms the [[geniculate ganglion]]. No other nerve in the body travels such a long distance through a bony canal. ===Branches=== ====Inside the facial canal==== * [[Greater petrosal nerve]] - provides parasympathetic innervation to lacrimal gland, as well as special taste sensory fibers to the palate via the [[nerve of pterygoid canal(Vidian Nerve)]]. * [[Nerve to stapedius]] - provides motor innervation for [[stapedius]] muscle in middle ear * [[Chorda tympani]] - provides parasympathetic innervation to [[submandibular gland]] and [[sublingual gland]] and special sensory taste fibers for the anterior 2/3 of the tongue. ====Outside skull (distal to [[stylomastoid foramen]])==== * [[Posterior auricular nerve]] - controls movements of some of the scalp muscles around the ear * Branch to Posterior belly of Digastric and Stylohyoid muscle * Five major facial branches (in parotid gland) - from top to bottom: ** [[Temporal branch of the facial nerve]] ** [[Zygomatic branch of the facial nerve]] ** [[Buccal branch of the facial nerve]] ** [[Marginal mandibular branch of the facial nerve]] ** [[Cervical branch of the facial nerve]] Helpful mnemonic devices for remembering the major branches are the phrases "To [[Zanzibar]] By Motor Car", "Two Zebras Bit My Cat" (or more popularly, albeit more crudely: "Two Zombies Buggered My Cat") and "Tell Ziggy [[Bob Marley]] Called". ==Embryology== The facial nerve is developmentally derived from the second pharyngeal ([[branchial arch]]). ==Function== ===Efferent=== Its main function is motor control of most of the [[facial muscles|muscles of facial expression]]. It also innervates the posterior belly of the [[digastric]] muscle, the [[stylohyoid]] muscle, and the [[stapedius]] muscle of the middle [[ear]]. All of these muscles are striated muscles of [[branchiomeric]] origin developing from the 2nd pharyngeal arch. The facial also supplies [[parasympathetic nervous system|parasympathetic]] fibers to the [[submandibular gland]] and [[sublingual gland]]s via [[chorda tympani]]. Parasympathetic innervation serves to increase the flow of saliva from these glands. It also supplies parasympathetic innervation to the nasal mucosa and the [[lacrimal gland]] via the [[pterygopalatine ganglion]]. The facial nerve also functions as the efferent limb of the [[corneal reflex]]. ===Afferent=== In addition, it receives [[taste]] sensations from the anterior two-thirds of the [[tongue]] and sends them to the nucleus of solitary tract. The facial nerve also supplies a small amount of afferent innervation to the [[oropharynx]] above the [[palatine tonsil]]. There is also a small amount of cutaneous sensation carried by the [[nervus intermedius]] from the skin in and around the [[auricle]] (earlobe). ==Location of Cell Bodies== The cell bodies for the facial nerve are grouped in anatomical areas called [[nucleus (neuroanatomy)|nuclei]] or [[ganglion|ganglia]]. The cell bodies for the afferent nerves are found in the [[geniculate ganglion]] for both taste and general afferent 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]]. ==Pathology== People may suffer from [[acute facial nerve paralysis]], which is usually manifested by facial paralysis. [[Bell's palsy]] is one type of [[idiopathic]] acute facial nerve paralysis, which is more accurately described as a multiple cranial nerve ganglionitis that involves the facial nerve, and most likely results from viral infection and also sometimes as a result of Lyme disease. ==Testing the facial nerve== Voluntary facial movements, such as wrinkling the brow, showing teeth, frowning, closing the eyes tightly ([[lagophthalmos]])<ref name=Lindgren>Kliniska Färdigheter: Informationsutbytet Mellan Patient Och Läkare, LINDGREN, STEFAN, ISBN 91-44-37271-X </ref> , pursing the lips and puffing out the cheeks, all test the facial nerve. There should be no noticeable asymmetry. In an [[upper motor neuron|UMN]] lesion, called [[central seven]], only the lower part of the face on the opposite side will be affected, due to the bilateral control to the upper facial muscles. [[Lower motor neuron]] lesions can result in [[Bell's palsy]], manifested as both upper and lower facial weakness on the same side of the lesion. Taste can be tested on the anterior 2/3 of the tongue. This can be tested with a swab dipped in a flavoured solution, or with electronic stimulation (similar to putting your tongue on a battery). ==Additional images== <gallery> Image:Gray507.png|Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries. Image:Gray567.png|Dura mater and its processes exposed by removing part of the right half of the skull, and the brain. Image:Gray689.png|Superficial dissection of brain-stem. Ventral view. Image:Gray719.png|Hind- and mid-brains; postero-lateral view. Image:Gray780.png|The sphenopalatine ganglion and its branches. Image:Gray781.png|Mandibular division of the trifacial nerve. Image:Gray782.png|Mandibular division of trifacial nerve, seen from the middle line. Image:Gray788.png|Plan of the facial and intermediate nerves and their communication with other nerves. Image:Gray789.png |The course and connections of the facial nerve in the [[temporal bone]]. Image:Gray792.png|Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ. Image:Gray911.png|View of the inner wall of the tympanum (enlarged.) Image:Gray912.png|The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above. Image:Gray922.png|Position of the right bony labyrinth of the ear in the skull, viewed from above. Image:Gray1209.png|Left temporal bone showing surface markings for the tympanic antrum (red), transverse sinus (blue), and facial nerve (yellow). Image:Gray1210.png|Side of neck, showing chief surface markings. Image:Illu cranial nerves.jpg|Cranial nerves Image:Head facial nerve branches.jpg|Head facial nerve branches </gallery> ==References== {{reflist}} ==External links== * {{eMedicine|ent|8}} * [http://www.med.harvard.edu/AANLIB/cases/caseM/mr1_t/015.html position of facial nerve on MRI] * [http://www.neuro.wustl.edu/neuromuscular/pathol/diagrams/viianat.htm WUSTL - map] {{Cranial nerves}} [[Category:Peripheral nervous system]] [[Category:Cranial nerves]] [[de:Nervus facialis]] [[es:Nervio facial]] [[fr:Nerf facial]] [[lt:Veidinis nervas]] [[hu:Arcideg]] [[it:Nervo faciale]] [[nl:Nervus facialis]] [[ja:顔面神経]] [[no:Nervus facialis]] [[pl:Nerw twarzowy]] [[pt:Nervo facial]] [[ru:Лицевой нерв]] [[sr:Живац лица]] [[fi:Kasvohermo]] [[sv:Ansiktsnerven]] [[zh:顏面神經]]