The Facial Nerve: Functional Components and
Anatomy
Brief overview of cranial nerve functional components
• The 12 cranial nerves participate in a total of seven neural functions. Each of these seven functions is designated by a three letter acronym.
• The first letter is either G (General) or S (Special).– General refers to primitive and/or external structures of the body.– Special refers to senses unique to the head (taste, olfaction, hearing, vision, and
balance) and to muscles of branchial arch derivatives.
• The second letter is either S (Somatic) or V (Visceral).– Somatic refers to non-visceral structures including skin, muscles, tendons, joints,
retina (vision), basilar membrane (hearing), and utricle/saccula (balance).– Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.
• The third letter is either A (Afferent) or E (Efferent).– Afferent refers to flow of neural information toward the brain (sensation)– Efferent refers to flow of neural information toward the periphery (motor).
• Knowledge of the functional components and the deficits that follow damage to each provides the basis of the thorough neurological exam.
The Seven Functional Components
• GSA – General Somatic Afferent– Touch, temperature, and pain from non-visceral structures
• GSE – General Somatic Efferent– Motor to skeletal muscle
• GVA – General Visceral Afferent– Touch (distention), temperature, and pain from the viscera
• GVE – General Visceral Efferent– Motor to viscera, smooth muscle, and glands
• SSA – Special Somatic Afferent– Vision, hearing, and balance
• SSE – Doesn’t exist
• SVA – Special Visceral Afferent
– Taste and olfaction
• SVE – Special Visceral Efferent– Motor to muscles derived from the branchial arches
The remainder of this tutorial focuses on the functional nerve components contained within the facial nerve:
SVEGVASVAGVEGSA
These components, either alone or in combination, make up the facial nerve and its branches. An understanding of these components can serve as a template for understanding the other functional components. In addition, an understanding of the facial nerve and its components can be applied in clinical situations to help localize a patient’s defect.
Functional Components Within Branches of the Facial Nerve:
• Greater Superficial Petrosal Nerve (GSPN)– GVA, GVE, SVA
• Stapedial Nerve– SVE
• Chorda Tympani Nerve– GVE, SVA
• Posterior Auricular Nerve– SVE, GSA
• Facial Nerve (terminal branch)– SVE
Anatomy of Facial Nerve Branches• The facial nerve exits the posterior cranial fossa (PCF) at the internal
acoustic meatus.• Within the internal acoustic meatus the facial nerve enters the facial
canal.• The first branch of the facial nerve, the greater superficial petrosal nerve
(GSPN) branches from the geniculate ganglion within the genu of the facial canal and enters the middle cranial fossa by way of the hiatus of the canal for the GSPN.
• The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.
• The third branch of the facial nerve, the chorda tympani nerve, branches from the descending portion of the facial nerve and enters the middle ear. Within the middle ear the chorda tympani nerve crosses the medial surface of the tympanic membrane. It then passes through the petrotympanic fissure to enter the infratemporal fossa.
• The descending portion of the facial nerve continues into the parotid region by way of the stylomastoid foramen.
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Petrotympanicfissure
Greater andlesser palatinecanals
Chorda tympani nerve
Facial nerve
Facial nerve
PosteriorCranialFossa (PCF)
Inferior Orbital Fissure
The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic meatus.
Click here to start Animation
Posteriorauricular N.
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Petrotympanicfissure
Greater andlesser palatinecanals
Chorda tympani
Facial nerve
Facial nerve
PosteriorCranialFossa
Inferior Orbital Fissure
Click here to start Animation
Within the internal acoustic meatus the facial nerve enters the facial canal.
Posteriorauricular N.
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Petrotympanicfissure
Greater andlesser palatinecanals
Chorda tympani
Facial nerve
Facial nerve
PosteriorCranialFossa
Inferior Orbital Fissure
Click here to start Animation
The first branch of the facial nerve, the greater superficial petrosal nerve (GSPN) branches from the geniculate ganglion within the genu of the facial canal and enters the middle cranial fossa (MCF) by way of the hiatus of the canal for the GSPN.
Geniculate ganglion
Facial canal
MCF
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Greater andlesser palatinecanals
Chorda tympani
Facial nerve
Facial nerve
PosteriorCranialFossa
Inferior Orbital Fissure
Click here to start Animation
The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.
Stapedial N. Petrotympanicfissure
Posteriorauricular N.
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Petrotympanicfissure
Greater andlesser palatinecanals
Chorda tympani N.
Facial nerve
Facial nerve
PosteriorCranialFossa
Inferior Orbital Fissure
Click here to start Animation
The third branch of the facial nerve, the chorda tympani nerve, branches from the descending portion of the facial nerve and enters the middle ear. Within the middle ear the chorda tympani nerve crosses the medial surface of the tympanic membrane. It then passes through the petrotympanic fissure to enter the infratemporal fossa.
Infratemporalfossa
Overview of Facial Nerve anatomy in the skull
Lacerate foramen
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Pterygoid canal
Greater superficialPetrosal nerve (GSPN)
Petrotympanicfissure
Greater andlesser palatinecanals
Chorda tympani
Facial nerve
Facial nerve
PosteriorCranialFossa
Inferior Orbital Fissure
Click here to start Animation
The descending portion of the facial nerve exits the facial canal at the stylomastoid foramen and continues into the parotid region
ParotidregionPosterior
auricular N.
Functional components of the Facial Nerve (CN VII)
• SVE (Special Visceral Efferent) — Motor to striated muscles derived from the 2nd branchial arch.
• GVA (General Visceral Afferent) — Sensory from visceral touch, temperature, and pain.
• SVA (Special Visceral Afferent) — Taste• GVE (General Visceral Efferent) — Autonomic
innervation to mucosal, lacrimal, and salivary glands.
• GSA (General Somatic Afferent) — Sensory from somatic touch, temperature, and pain.
1.
2.
3.
4.
5.
Click on numbers for functional components
SVE Component of theFacial Nerve
The next 11 slides demonstrate innervation to muscles derived from the 2nd branchial arch:
1. Stapedius muscle -- dampens movement of the ossicles (inserts on stapes of middle ear)
2. Posterior auricular muscle -- posterior movement of pinna
3. Stylohyoid muscle -- elevates hyoid bone4. Posterior belly of digastric -- elevates hyoid
bone, depresses mandible5. Muscles of facial expression -- blinking, smiling,
frowning, facial movements
Click here to start Animation of SVE component
\Stapedius muscle dampens movement of the ossicles protecting the inner ear from damage from loud noises
SVE
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1. The Stapedius muscle dampens movement of the ossicles
2. The Posterior Auricular nerve innervates the posterior auricular muscle, pulling the pinna posteriorly.
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SVE component of posterior auricular nerve
Posterior auricularmuscle pulls the pinna posteriorly
SVE
Stylohyoid muscle elevates the hyoid bone.
Through the internalAcoustic meatus
Through the stylomastoidforamen
3. The Stylohyoid muscle elevates the hyoid bone
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Stylohyoid branch of facial nerveinnervates stylohyoid muscle
SVE
Through the stylomastoidforamen
4. The Posterior belly of digastric muscle elevates the hyoid bone
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Posterior belly of digastric branch of facial nerveinnervates posterior belly of digastric muscle.
Posterior belly of digastric muscle elevates the hyoid bone
SVEThrough the internalacoustic meatus
5. The next six slides demonstrate SVE innervation to the muscles of facial expression*
A. Temporal branch (with zygomatic branch) innervates orbicularis oculi--closes eyelids
B. Zygomatic branch (with buccal branch) innervates zygomaticus major--smiling
C. Buccal branch innervatesbuccinator--tenses cheek
D. Mandibular branch innervates depressor angularis oris--frowning
E. Cervical branch innervates platysma -- lowers mandible, tenses skin of anterior neck
*These are key innervations to the muscles of facial expression. However, each nerve branch innervates multiple muscles and each muscle receives multiple nerve branches.
SVE
A. The temporal and zygomatic branches of the facial nerve provide SVE nerve fibers that innervate the ipsilateral orbicularis oculi, the muscle responsible for closing the eyelid.
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Temporal branch
Zygomatic branch
SVEContraction of orbicularisoculi causes the eyelid to close
B. The zygomatic and buccal branches of the facial nerve innervate the ipsilateral zygomaticus major muscle, the main muscle responsible for smiling.
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Zygomatic branch
SVE
Zygomaticus major muscle
Contraction of the zygomaticus major musclecauses smiling
C. The buccal branch of the facial nerve innervates the buccinator muscle, the muscle responsible for holding the cheek against the teeth, thus positioning food for chewing.
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Buccal branch offacial nerve innervatesBuccinator muscle.
SVE Contraction of the buccinator musclecauses tensing of the cheek whichhelps position food within the occusal planefor chewing
D. The mandibular and buccal branches of the facial nerve innervate the ipsilateral depressor angularis oris muscle, a muscle responsible for frowning.
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Mandibular branch
SVE
Depressorangularis oris
Contraction of thedepressor angularis orismuscle causes frowning
E. The cervical branch of the facial nerve innervates the platysma muscle, a muscle partly responsible for depressing the mandible.
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Platysma muscle
Cervical branch offacial nerve innervates
Platysma muscle.
Contraction of platysmaMuscle results in depressionof mandible.
SVE
E. The cervical branch of the facial nerve innervates the platysma muscle (the “shaving muscle”), a muscle responsible for tightening the skin of the anterior neck.
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Platysma muscle
Cervical branch offacial nerve innervates
Platysma muscle.
Contraction of platysmamuscle causes the skin of the anterior neck to tighten.
SVE
Stapedius muscle dampens movement of ossicles.
Summary of SVE
Facial canal
Internal AcousticMeatus
StylomastoidForamen
Click here to start Animation
Temporal-orbicularis oculi closes eyelids.Zygomatic-zygomaticus majorpartly responsible for smiling.Buccal-buccinator tenses cheekMandibular-depressor angularis oris responsible for frowning.Cervical- platysma helps lower mandible and tightens skin of neck.
Posterior auricularmuscle responsible forposterior displacementof pinna.
Facial nerve
Facial nerve
Posterior belly of digastricelevates hyoid bone.
Stylohyoid muscleelevates hyoid bone.
Posteriorauricular N.
Facialnucleus
GVA Component of the Facial Nerve
The next slide demonstrates that GVA is responsible for providing:
1. Light touch, temperature, and pain sensation from the soft palate via the greater superficial petrosal nerve (GSPN).
Click here to start GVA
1. GVA provides sensation of light touch, temperature, and pain from the soft palate.
soft palate
Light touch, temperature,and pain fromthe soft palate
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GVA
Light touch sensation
Temperature sensation
Pain sensation
GSPN
Facial nerve
Through the hiatus of canal of GSPN
Light touch, temperature, and pain from the soft palate
Through the internal acoustic meatus
Summary of GVA
Through the Pterygoid canal
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Pterygoid canal
Facial canal
Through the lesser palatinecanalGSPN
Facial nerve
SVA Component of the Facial Nerve
The next two slides demonstrate that SVA is responsible for providing:
1. Taste from the hard and soft palate via the greater superficial petrosal nerve (GSPN).
2. Taste from the anterior 2/3 of the tongue via the chorda tympani nerve.
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1. SVA provides taste sensation from the hard and soft palate via the GSPN.
Soft palate
Taste from the hard and soft palate
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Hard palate
CoSweetened coffee
SVA
GSPN branches fromthe facial nerve at thegeniculate ganglion within the genu of thefacial canal. It is made upof fibers from SVA,GVE, and GVA.
2. SVA provides taste to the anterior 2/3 of the tongue via the chorda tympani nerve.
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Taste from the anterior 2/3 of the tongue
SVA
Chorda tympani
Taste from hard and soft palate.
Summary of SVA
Lacerate foramen
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Facial canal
Internal AcousticMeatus
StylomastoidForamen
Hiatus of canal of greater superficial petrosal nerve
Taste from anterior 2/3 tongue.
Pterygoid canal
Chorda tympani
GSPN
Petrotympanicfissure
Greater andlesser palatinecanals
GVE Component of theFacial Nerve
1. Via the pterygopalatine ganglion GVE provides:
A. Lacrimation (tearing of the eye)
B. Mucus secretions of the nasal cavity
C. Mucus secretions of the oral cavity
2. Via innervation of the submandibular ganglion GVE provides:
A. Salivation of the oral cavity
Click to start Animation of GVE component
1. The GVE component of the facial nerve transmits preganglionic fibers to the pterygopalatine ganglion via the GSPN. From the pterygopalatine ganglion postganglionic fibers cause ipsilateral
lacrimation and mucus secretions of the nasal and oral cavities.
Pterygopalatineganglion
Lacrimal nucleus
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A. Tearing of eye
B. Mucus secretion of nasal cavities
C. Mucus secretion of hard and soft palate.
GVELacrimal gland
GSPN
2. The GVE component of the facial nerve transmits preganglionic fibers to the submandibular ganglion via the chorda tympani nerve. From the submandibular ganglion postganglionic fibers innervate the submandibular and sublingual glands, causing salivation.
Superior salivary nucleus
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Submandibularganglion
Submandibulargland
Sublingulalgland
GVE
Chordatympani
Summary of GVE
Lacerate foramen
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Facial canal
Internal AcousticMeatus
Superior salivary and lacrimal nucleus
Pterygoid canal
From the pterygopalatine ganglionpostganglionic GVE fibersprovide lacrimation of theeyes and mucus secretion of thenasal cavity and oral cavity.
From the submandibularganglion postganglionicGVE fibers providesalivation in the oral cavity.
Petrotympanic fissure
Chorda tympani
GSPN
Hiatus of canal of greater superficial petrosal nerve
Inferior Orbital Fissure
Greater andlesser palatinecanals
GSA Component of theFacial Nerve
GSA is responsible for providing:
1. Touch, temperature, and pain sensation from part of the external acoustic meatus via the posterior auricular nerve.
Click here to start GSA
1. GSA provides touch, temperature, and pain sensation from the external acoustic meatus.
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Cotton swab
Touch, temperature, and pain sensation from part of the external acoustic meatus.
GSA
Posteriorauricularnerve
Touch, temperature, and pain sensation from the external acoustic meatus.
Summary of GSA
Internal AcousticMeatus
StylomastoidForamen
Foramen Rotundem Inferior Orbital Fissure
Click here to start animation
Facial canal
Facial nerve
Facial nerve
Posteriorauricularnerve
Summary of functional components
• Each of the five functional components of the facial nerve SVE, GVA, SVA, GVE, and GSA have a unique function. Knowledge of these functional components can be applied to clinical observations to aid in localizing lesions of nerve branches or at anatomical landmarks.
• The following slides provide examples of how lesions at different locations can effect function.
Question #1
A. Paralysis of facial muscles
B. Decreased sensation soft palate
C. Decreased hearing sensivity
D. Loss of taste to the soft palate
A. Paralysis of facial muscles
B. Decreased sensation of soft palate
C. Increased sensitivity to loud noise
D. Loss of taste of hard palate
One effect of a lesion here, between the branching of the stapedial nerve and the branching of the chorda tympani nerve, would be:
Question #2
A lesion here, between the branching of the stapedial nerve and the branching of the chorda tympani nerve, will also cause?
A. Loss of light touch from the soft palate
B. Loss of taste from the soft palate
C. Loss of taste of anterior 2/3 of tongue
D. Loss of temperature from the soft palate.
Question #3
One effect of a lesion here, at the stylomastoid foramen will be:
A. Loss of light touch from the soft palate
B. Loss of salivation of oral cavity
C. Increased sensitivity to loud noises
D.Partial loss of sensation of external acoustic meatus
Question #4
A lesion here, between the branching of the GSPN and the branching of the stapedial nerve, will spare:
A. Taste of anterior 2/3 of tongue
B. Taste of hard palate
C. Salivation in oral cavity
D. Ipsilateral facial expression
Question #5
A lesion here, between the branching of the GSPN and the branching of the stapedial nerve, will also spare:
A. Light touch from the soft palate
B. Ability to smile
C. Taste from the anterior 2/3 of tongue
D. Protection of the inner ear from loud noises
Thank You
Return to SVE Return to GVA Return to SVA
Return to GVE Return to GSA
Return to Lesion Questions
IncorrectThe GVA component of the GSPN, which is spared by this lesion,
is responsible for providing sensation from the soft palate.
Please try again
IncorrectThe stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud noises.
Please try again
Incorrect The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the hard palate.
Please try again
IncorrectThe GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
Incorrect The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the soft palate.
Please try again
IncorrectThe GVA component of the GSPN, which is spared by this lesion,
is responsible for providing temperature sensation from the soft palate.
Please try again
IncorrectThe GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
IncorrectThe GVE component of the chorda tympani nerve, which is spared
by this lesion, is responsible for providing salivation of the oral cavity.
Please try again
Incorrect The stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud noises.
Please try again
IncorrectThis lesion will not spare taste to the anterior 2/3 of the tongue, which is supplied via the SVA component of the chorda tympani
nerve.
Please try again
IncorrectThis lesion will not spare salivation of the oral cavity, which is supplied by the GVE component of the chorda tympani nerve.
Please try again
IncorrectThis lesion will not spare ipsilateral facial expression, which is supplied by the temporal, zygomatic, buccal, mandibular, and
cervical branches of the facial nerve (SVE).
Please try again
IncorrectThis lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
IncorrectThis lesion will not spare the ability to taste from the anterior 2/3 of the tongue, which is supplied by the SVA component of the chorda
tympani nerve.
Please try again
IncorrectThis lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
IncorrectThis lesion will not spare the ability to protect the ear from loud
noises, which is supplied by the stapedial nerve (SVE).
Please try again
Correct!A lesion here will cause paralysis of facial muscles due
to its disruption of the SVE component.
Next questionGo back to question 1
Correct!A lesion here will cause a loss of taste to the anterior 2/3 of the
tongue due to the disruption of the SVA component of the chorda tympani nerve.
Next questionGo back to question 2
Correct!A lesion here will cause partial loss of sensation (light touch,
temperature, and pain) of the external acoustic meatus due to disruption of the GSA component of the posterior auricular nerve.
Next questionGo back to question 3
Correct!A lesion here will spare a person’s ability to taste on the hard and soft
palate because the SVA component of the Greater Superficial Petrosal Nerve (GSPN) remains intact.
Next questionGo back to question 4
Correct!A lesion here will spare the sensation of light touch of the soft palate
because the GVA component of the GSPN remains intact.
Go back to question 5 Continue