The facial nerve is the seventh cranial nerve. It emerges from the brainstem between the pons and medulla and controls the muscles of facial expression and taste to the front two-thirds of the tongue. The facial nerve has motor, sensory, and parasympathetic components. It innervates the muscles of facial expression and provides parasympathetic fibers to salivary and lacrimal glands.

1. TheThe facial nervefacial nerve is the seventh (VII) ofis the seventh (VII) of
twelve pairedtwelve paired cranial nervescranial nerves. It emerges from. It emerges from
the brainstem between thethe brainstem between the ponspons and theand the
medullamedulla, and controls the muscles of facial, and controls the muscles of facial
expression, andexpression, and tastetaste to the anterior two-to the anterior two-
thirds of thethirds of the tonguetongue. It also has preganglionic. It also has preganglionic
parasympatheticparasympathetic fibers to several head andfibers to several head and
neckneck gangliaganglia..

2. StructureStructure
 1.The motor part of the facial nerve include1.The motor part of the facial nerve include
thethe facial nerve nucleusfacial nerve nucleus in thein the ponspons
 2.The sensory part of the facial nerve include2.The sensory part of the facial nerve include
thethe nervusnervus intermediusintermedius..

3. nucleusnucleus
 The cell bodies for the afferent nerves are found inThe cell bodies for the afferent nerves are found in
thethe geniculategeniculate ganglionganglion for both taste and generalfor both taste and general
afferent sensation. /nucleus tractus solitarii/afferent sensation. /nucleus tractus solitarii/
 The cell bodies for muscular efferent nerves areThe cell bodies for muscular efferent nerves are
found in thefound in the facial motor nucleusfacial motor nucleus The nucleus has aThe nucleus has a
dorsal and ventral region, with neurons in the dorsaldorsal and ventral region, with neurons in the dorsal
region innervating muscles of the upper face andregion innervating muscles of the upper face and
neurons in the ventral region innervating muscles ofneurons in the ventral region innervating muscles of
the lower face.the lower face.
 the cell bodies for the parasympathetic efferentthe cell bodies for the parasympathetic efferent
nerves are found in thenerves are found in the superiorsuperior salivatorysalivatory nucleusnucleus

6. AnatomyAnatomy
 The nucleus is situated in the caudal portion ofThe nucleus is situated in the caudal portion of
the ventrolateralthe ventrolateral pontinepontine tegmentumtegmentum. Its axons. Its axons
take an unusual course, traveling dorsally andtake an unusual course, traveling dorsally and
looping around thelooping around the abducensabducens nucleusnucleus, then, then
traveling ventrally to exit the ventral ponstraveling ventrally to exit the ventral pons
medial to themedial to the spinalspinal trigeminaltrigeminal nucleusnucleus. These. These
axons form the motor component of theaxons form the motor component of the
facial nervefacial nerve,, parasympatheticparasympathetic andand sensorysensory
components forming thecomponents forming the nervusnervus intermediusintermedius

7. Parasympathetic fibersParasympathetic fibers
 TheThe superiorsuperior salivatorysalivatory nucleusnucleus contains the cell bodies of parasympatheticcontains the cell bodies of parasympathetic
axons within the nervus intermedius. These fibers reach the geniculateaxons within the nervus intermedius. These fibers reach the geniculate
ganglion but do not synapse. Some of these preganglionic parasympatheticganglion but do not synapse. Some of these preganglionic parasympathetic
fibers persist within thefibers persist within the greatergreater petrosalpetrosal nervenerve as they exit the geniculateas they exit the geniculate
ganglion and subsequently synapse with neurons in theganglion and subsequently synapse with neurons in the pterygopalatinepterygopalatine
ganglionganglion. These postganglionic neurons send. These postganglionic neurons send axonsaxons that providethat provide
parasympathetic innervation to theparasympathetic innervation to the lacrimallacrimal glandgland..
 The remaining preganglionic fibers continue as the mixed facial nerveThe remaining preganglionic fibers continue as the mixed facial nerve
proper as it extends through the facial canal. Before the nerve exits theproper as it extends through the facial canal. Before the nerve exits the
skull via theskull via the stylomastoidstylomastoid foramenforamen and after theand after the nerve to thenerve to the stapediusstapedius
musclemuscle has branched off, the facial nerve gives off thehas branched off, the facial nerve gives off the chordachorda
tympani nervetympani nerve. This nerve exits the skull through the. This nerve exits the skull through the pterygotympanicpterygotympanic
fissurefissure and merges with theand merges with the lingual nervelingual nerve, after which it synapses with, after which it synapses with
neurons in theneurons in the submandibularsubmandibular ganglionganglion. These postganglionic neurons. These postganglionic neurons
provide parasympathetic innervation to theprovide parasympathetic innervation to the submandibularsubmandibular andand
sublingual glandssublingual glands

8. Sensory fibersSensory fibers
 The sensory component of the nervus intermedius carries inputThe sensory component of the nervus intermedius carries input
about sensation from the skin of theabout sensation from the skin of the external auditoryexternal auditory meatusmeatus,,
from thefrom the mucous membranesmucous membranes of theof the nasopharynxnasopharynx andand nosenose, and, and
tastetaste from the anterior two-thirds of thefrom the anterior two-thirds of the tonguetongue, floor of the, floor of the
mouth, and themouth, and the palatepalate. The sensory information from the. The sensory information from the
mucous membranesmucous membranes of the nasopharynx and palate is carriedof the nasopharynx and palate is carried
along the greater petrosal nerve, while the chorda tympanialong the greater petrosal nerve, while the chorda tympani
nerve (and lingual nerve) carries taste input from the anteriornerve (and lingual nerve) carries taste input from the anterior
two-thirds of the tonge, floor of mouth, and palate.two-thirds of the tonge, floor of mouth, and palate.
 The geniculate ganglion contains the cell bodies of the sensoryThe geniculate ganglion contains the cell bodies of the sensory
component of the nervus intermedius.component of the nervus intermedius.

9. Motor fibersMotor fibers
 The motor part of the facial nerve enters intoThe motor part of the facial nerve enters into
thethe internal auditoryinternal auditory meatusmeatus then runs athen runs a
tortuous course (including two tight turns)tortuous course (including two tight turns)
through thethrough the facial canalfacial canal, emerges from the, emerges from the
stylomastoidstylomastoid foramenforamen and passes through theand passes through the
parotid glandparotid gland, where it divides into five major, where it divides into five major
branches. Though it passes through the parotidbranches. Though it passes through the parotid
gland, it does not innervate the gland. Thisgland, it does not innervate the gland. This
action is the responsibility of cranial nerve IX,action is the responsibility of cranial nerve IX,
thethe glossopharyngealglossopharyngeal nervenerve..

10. BranchesBranches
 Inside the facial canalInside the facial canal
 GreaterGreater petrosalpetrosal nervenerve - provides parasympathetic- provides parasympathetic
innervation to lacrimal gland, as well as special tasteinnervation to lacrimal gland, as well as special taste
sensory fibers to the palate via thesensory fibers to the palate via the nerve ofnerve of pterygoidpterygoid
canalcanal..
 Nerve toNerve to stapediusstapedius - provides motor innervation for- provides motor innervation for
stapediusstapedius muscle in middle earmuscle in middle ear
 ChordaChorda tympanitympani - provides parasympathetic- provides parasympathetic
innervation to submandibular and sublingual glandsinnervation to submandibular and sublingual glands
and special sensory taste fibers for the anterior 2/3 ofand special sensory taste fibers for the anterior 2/3 of
the tongue.the tongue.

11. Outside skullOutside skull
 Posterior auricular nervePosterior auricular nerve - controls movements- controls movements
of some of the scalp muscles around the earof some of the scalp muscles around the ear
 Five major facial branches (in parotid gland) -Five major facial branches (in parotid gland) -
from top to bottom:from top to bottom:
 Temporal branch of the facial nerveTemporal branch of the facial nerve
 ZygomaticZygomatic branch of the facial nervebranch of the facial nerve
 BuccalBuccal branch of the facial nervebranch of the facial nerve
 MarginalMarginal mandibularmandibular branch of the facial nervebranch of the facial nerve
 Cervical branch of the facial nerveCervical branch of the facial nerve

12. FunctionFunction
 EfferentEfferent
 Its main function is motor control of most of theIts main function is motor control of most of the
muscles of facial expressionmuscles of facial expression. It also innervates the posterior belly of the. It also innervates the posterior belly of the
digastricdigastric muscle, themuscle, the stylohyoidstylohyoid muscle, and themuscle, and the stapediusstapedius muscle of themuscle of the
middlemiddle earear..
 The facial also suppliesThe facial also supplies parasympatheticparasympathetic fibers to thefibers to the submandibularsubmandibular glandgland
andand sublingual glandssublingual glands viavia chordachorda tympanitympani and theand the submandibularsubmandibular ganglionganglion..
Parasympathetic innervation serves to increase the flow of saliva fromParasympathetic innervation serves to increase the flow of saliva from
these glands. It also supplies parasympathetic innervation to the nasalthese glands. It also supplies parasympathetic innervation to the nasal
mucosa and themucosa and the lacrimallacrimal glandgland via thevia the pterygopalatinepterygopalatine ganglionganglion..
 AfferentAfferent
 It isIt is tastetaste sensations from the anterior two-thirds of thesensations from the anterior two-thirds of the tonguetongue. The facial. The facial
nerve also supplies a small amount of afferent innervation to thenerve also supplies a small amount of afferent innervation to the
oropharynxoropharynx above theabove the palatine tonsilpalatine tonsil. There is also a small amount of. There is also a small amount of
cutaneous sensation carried by thecutaneous sensation carried by the nervusnervus intermediusintermedius from the skin in andfrom the skin in and
around thearound the auricleauricle

13. Testing the facial nerveTesting the facial nerve
 Voluntary facial movements, such as wrinkling the brow, showing teeth,Voluntary facial movements, such as wrinkling the brow, showing teeth,
frowning, closing the eyes tightly (lagophthalmos) , pursing the lips andfrowning, closing the eyes tightly (lagophthalmos) , pursing the lips and
puffing out the cheeks, all test the facial nerve. There should be nopuffing out the cheeks, all test the facial nerve. There should be no
noticeable asymmetry.noticeable asymmetry.
 In an upper motor neuron lesion, called central seven, only the lower partIn an upper motor neuron lesion, called central seven, only the lower part
of the face on the opposite side will be affected, due to the bilateral controlof the face on the opposite side will be affected, due to the bilateral control
to the upper facial muscles.to the upper facial muscles.
 Lower motor neuron lesions can result in Bell's palsy, manifested as bothLower motor neuron lesions can result in Bell's palsy, manifested as both
upper and lower facial weakness on the same side of the lesion.upper and lower facial weakness on the same side of the lesion.
 Taste can be tested on the anterior of the tongue. This can be tested with aTaste can be tested on the anterior of the tongue. This can be tested with a
swab dipped in a flavoured solution, or with electronic stimulation (similarswab dipped in a flavoured solution, or with electronic stimulation (similar
to putting your tongue on a battery).to putting your tongue on a battery).
 Facial nerve can also be tested because it controls about 2/3 of the tongue.Facial nerve can also be tested because it controls about 2/3 of the tongue.
Try making your finger moist, and dipping it in some sugar, or saltTry making your finger moist, and dipping it in some sugar, or salt
(something sweet/salty) then touch your finger to the back of your tongue.(something sweet/salty) then touch your finger to the back of your tongue.
See if you can taste it!See if you can taste it!