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]]