Motor ( SVE ) - muscles of facial expression ,
stapedius , stylohyoid
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posterior belly of digastric?
Secretomotor ( GVE ) - lacrimal gland , glands in m.m. of nose, PNS , palate & nasopharynx
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submandibular , sublingual and other minor salivary glands ,
mucosal glands in oral cavity
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?Sensory ( SVA ) - taste from anterior 2/3 of tongue
from floor of oral cavity & palate
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?
Sensory ( GSA ) - from EAC ( ext. auditory canal )
Facial nerve nuclei
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Main motor nucleus ( SVE )
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?Parasympathetic nuclei ( Superior salivatory nucleus & lacrimatory nucleus - GVE )
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Sensory nuclei ( Nucleus of Tractus Solitarius - SVA ,
Spinal part of Sensory nucleus of CN V - GSA )
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Main motor nucleus
> lies deep in the reticular formation of lower part of pons
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> supplies muscles derived from 2nd branchial arch> supranuclear connections - IMPORTANT
Upper part of nucleus receives corticonuclear fibres from both cerebral hemispheres
Lower part of nucleus receives only contralateral corticonuclear fibres
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These connections have important bearing on clinical presentation of lesions affectingfacial nerve .
These connections explain voluntary control of facial muscles .
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Another INVOLUNTARY pathway exists ?It is separate & controls mimetic / emotional changes in facial expression .
It forms part of reticular formation .
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Parasympathetic nuclei
> lie posterolateral to main motor nucleus
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> they are superior salivatory nucleus& lacrimal nucleus
Neurons of the 2 nuclei seem to be intermingled with each other and exact location of these
nuclei in humans are uncertain
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> receives afferent fibers from -
1. hypothalamus through autonomic descending pathways
2. taste fibers ascending from NTS
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> lacrimal nucleus receives afferent fibers from1. hypothalamus for emotional responses
2. sensory nuclei of CN V for reflex lacrimation .
?
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Sensory nucleui - NTS ( SVA) , Spinal nucleus of CN V ( GSA )
> upper part of NTS (nucleus of tractus solitarius ) lies close to motor nucleus
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> taste pathway -
Receptors ( taste buds )
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1st order neuron ( geniculate ganglia )
NTS
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2nd order neuron
cross the median plane and ascend to
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VPMN ( ventral posteromedial nucleus )of opposite thalamus& to a number of hypothalamic nuclei -
3rd order neuron
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from thalamus pass through internal capsule & corona-radiata to end in taste area of the cortex in
lower part of post central gyrus ( insular cortex ) .
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?
Sensory nuclei cont'd .....
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> sGSA fibers fromconcha of EAC &
retroauricular groove region
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will reach thesensory nucleus of CN V
(after entering brainstem) &
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then run with the CN VBranches of facial nerve
?
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Greater superficial petrosal nerve?
Nerve to stapedius
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Chorda tympani
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?Communicating branch
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Posterior auricular nerve
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Muscular branches?
Peripheral branches -
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> 2 divisions entering the parotid are temporofacial / temporozygomatic
& cervicofacial
they form a network of nerves within parotid ( pes anserinus /goose foot )
the plexus gives of five / five group of branches
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these branches leave the parotid and diverge into there area of distributionbranches are ?
1. temporal
2. zygomatic
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3. buccal4. mandibular
5. cervical
> they supply all muscles of facial expression
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Course of facial nerve
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Motor rootStarting from motor nucleus first travels posteriorly around the medial side of abducent nucleus &
then loops around the nucleus of CNVI coming lateral to it . This loop of facial nerve lies in the floor
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of IV th ventricle & produces an elevation in the ventricle called facial colliculus .
After looping around nucleus of CN VI it passes anteriorly to emerge from brainstem .
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?Sensory root ( nervus intermedius / nerve of Wrisberg ) made of
1. central processes of unipolar cells of geniculate ganglion
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2. parasympathetic fibers ?
efferent preganglionic parasympathetic fibers from superior salivatory and lacrimal nuclei .
?
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The course of the facial nerve can be divided into> intracranial - 24mm ( 5-12mm in IAC )
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> intratemporal - 28 ? 30 mm , facial (fallopian) canal ;labyrinthine segment - 3-5mm
first genu ( geniculate ganglion) -
tympanic segment 8-11mm
second genu
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mastoid segment 12 ? 20mmstylomastoid foramen
> extratemporal portions
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