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.
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The second letter is either S (Somatic) or V (Visceral).
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The third letter is either A (Afferent) or E (Efferent).
– 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. – Afferent refers to flow of neural information toward the brain (sensation) – Efferent refers to flow of neural information toward the periphery (motor).
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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
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GSE – General Somatic Efferent – Motor to skeletal muscle
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GVA – General Visceral Afferent – Touch (distention), temperature, and pain from the viscera
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GVE – General Visceral Efferent – Motor to viscera, smooth muscle, and glands
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SSA – Special Somatic Afferent – Vision, hearing, and balance
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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: SVE GVA SVA GVE GSA 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 • • •
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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
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus Posterior Cranial Fossa (PCF)
Inferior Orbital Fissure Lacerate foramen
Greater superficial Petrosal nerve (GSPN)
Facial canal
Pterygoid canal
Greater and lesser palatine canals
Petrotympanic fissure
Facial nerve
Stylomastoid Foramen
Chorda tympani nerve
Facial nerve Posterior auricular N.
The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic meatus.
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Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus Posterior Cranial Fossa
Inferior Orbital Fissure Lacerate foramen
Pterygoid canal
Greater superficial Petrosal nerve (GSPN)
Facial canal
Petrotympanic fissure
Facial nerve
Stylomastoid Foramen
Chorda tympani
Facial nerve Posterior auricular N.
Within the internal acoustic meatus the facial nerve enters the facial canal.
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Greater and lesser palatine canals
Overview of Facial Nerve anatomy in the skull
Inferior Orbital Fissure Hiatus of canal of greater superficial petrosal nerve
Lacerate foramen
Geniculate ganglion
MCF Internal Acoustic Meatus Posterior Cranial Fossa
Pterygoid canal
Greater superficial Petrosal nerve (GSPN)
Facial canal
Greater and lesser palatine canals
Petrotympanic fissure
Facial nerve
Stylomastoid Foramen
Chorda tympani
Facial nerve
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.
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Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus Posterior Cranial Fossa
Inferior Orbital Fissure Lacerate foramen
Pterygoid canal
Greater superficial Petrosal nerve (GSPN)
Facial canal
Stapedial N.
Greater and lesser palatine canals
Petrotympanic fissure
Facial nerve
Stylomastoid Foramen
Chorda tympani
Facial nerve Posterior auricular N.
The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.
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Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus Posterior Cranial Fossa
Inferior Orbital Fissure Lacerate foramen
Greater superficial Petrosal nerve (GSPN)
Facial canal
Pterygoid canal
Greater and lesser palatine canals
Petrotympanic fissure
Facial nerve Chorda tympani N.
Stylomastoid Foramen
Infratemporal fossa
Facial nerve
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.
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Overview of Facial Nerve anatomy in the skull
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus Posterior Cranial Fossa
Inferior Orbital Fissure Lacerate foramen
Pterygoid canal
Greater superficial Petrosal nerve (GSPN)
Facial canal
Petrotympanic fissure
Facial nerve
Stylomastoid Foramen Facial nerve Posterior auricular N.
Chorda tympani
Parotid region
The descending portion of the facial nerve exits the facial canal at the stylomastoid foramen and continues into the parotid region
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Greater and lesser palatine canals
Functional components of the Facial Nerve (CN VII) 1.
2. 3. 4.
5.
• 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. Click on numbers for functional components
SVE Component of the
 Facial Nerve 1. 2. 3. 4. 5.
The next 11 slides demonstrate innervation to muscles derived from the 2nd branchial arch: Stapedius muscle -- dampens movement of the ossicles (inserts on stapes of middle ear) Posterior auricular muscle -- posterior movement of pinna Stylohyoid muscle -- elevates hyoid bone Posterior belly of digastric -- elevates hyoid bone, depresses mandible Muscles of facial expression -- blinking, smiling, frowning, facial movements Click here to start Animation of SVE component
1. The Stapedius muscle dampens movement of the ossicles
SVE
\ Stapedius muscle dampens movement of the ossicles protecting the inner ear from damage from loud noises
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2. The Posterior Auricular nerve innervates the posterior auricular muscle, pulling the pinna posteriorly.
SVE
Posterior auricular muscle pulls the pinna posteriorly
SVE component of posterior auricular nerve
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3. The Stylohyoid muscle elevates the hyoid bone SVE Through the internal Acoustic meatus
Stylohyoid muscle elevates the hyoid bone.
Through the stylomastoid foramen
Stylohyoid branch of facial nerve innervates stylohyoid muscle
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4. The Posterior belly of digastric muscle elevates the hyoid bone
SVE Through the internal acoustic meatus
Posterior belly of digastric muscle elevates the hyoid bone
Through the stylomastoid foramen
Posterior belly of digastric branch of facial nerve innervates posterior belly of digastric muscle.
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5. The next six slides demonstrate SVE innervation to the muscles of facial expression*
SVE
A.
Temporal branch (with zygomatic branch) innervates orbicularis oculi--closes eyelids
B.
Zygomatic branch (with buccal branch) innervates zygomaticus major--smiling
C.
Buccal branch innervates buccinator--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.
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. Contraction of orbicularis oculi causes the eyelid to close
SVE
Temporal branch
Zygomatic branch
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B. The zygomatic and buccal branches of the facial nerve innervate the ipsilateral zygomaticus major muscle, the main muscle responsible for smiling. SVE Zygomaticus major muscle
Zygomatic branch Contraction of the zygomaticus major muscle causes smiling
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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.
SVE
Contraction of the buccinator muscle causes tensing of the cheek which helps position food within the occusal plane for chewing
Buccal branch of facial nerve innervates Buccinator muscle.
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D. The mandibular and buccal branches of the facial nerve innervate the ipsilateral depressor angularis oris muscle, a muscle responsible for frowning.
SVE
Mandibular branch Depressor angularis oris
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Contraction of the depressor angularis oris muscle causes frowning
E. The cervical branch of the facial nerve innervates the platysma muscle, a muscle partly responsible for depressing the mandible.
SVE
Contraction of platysma Muscle results in depression of mandible.
Platysma muscle
Cervical branch of facial nerve innervates Platysma muscle.
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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.
SVE Contraction of platysma muscle causes the skin of the anterior neck to tighten.
Platysma muscle
Cervical branch of facial nerve innervates Platysma muscle.
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Summary of SVE
Internal Acoustic Meatus
Facial nucleus
Stapedius muscle dampens movement of ossicles.
Facial canal
Facial nerve Stylomastoid Foramen
Facial nerve
Posterior auricular N. Posterior auricular muscle responsible for posterior displacement of pinna. Stylohyoid muscle elevates hyoid bone.
Posterior belly of digastric elevates hyoid bone.
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Temporal-orbicularis oculi closes eyelids. Zygomatic-zygomaticus major partly responsible for smiling. Buccal-buccinator tenses cheek Mandibular-depressor angularis oris responsible for frowning. Cervical- platysma helps lower mandible and tightens skin of neck.
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.

GVA
Temperature sensation
GSPN
soft palate
Light touch sensation Pain sensation Facial nerve
Light touch, temperature, and pain from the soft palate
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Through the Pterygoid canal
Summary of GVA
Through the hiatus of canal of GSPN
GSPN
Through the internal acoustic meatus
Facial canal
Facial nerve
Light touch, temperature, and pain from the soft palate
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Pterygoid canal
Through the lesser palatine canal
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. Click here for animation
1. SVA provides taste sensation from the hard and soft palate via the GSPN.

SVA
Hard palate
Soft palate GSPN branches from the facial nerve at the geniculate ganglion within the genu of the facial canal. It is made up of fibers from SVA, GVE, and GVA.
Co Sweetened coffee
Taste from the hard and soft palate
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2. SVA provides taste to the anterior 2/3 of the tongue via the chorda tympani nerve. SVA
Chorda tympani
Taste from the anterior 2/3 of the tongue
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Summary of SVA
Hiatus of canal of greater superficial petrosal nerve
Internal Acoustic Meatus
Lacerate foramen
GSPN
Pterygoid canal
Facial canal
Petrotympanic fissure
Chorda tympani Taste from hard and soft palate.
Stylomastoid Foramen
Taste from anterior 2/3 tongue.
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Greater and lesser palatine canals
GVE Component of the
 Facial 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
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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.
GVE
GSPN
Lacrimal gland Pterygopalatine ganglion
A. Tearing of eye Lacrimal nucleus B. Mucus secretion of nasal cavities
C. Mucus secretion of hard and soft palate.
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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.
GVE Sublingulal gland
Submandibular gland Superior salivary nucleus Chorda tympani Submandibular ganglion
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Summary of GVE
Hiatus of canal of greater superficial petrosal nerve
Inferior Orbital Fissure Lacerate foramen GSPN
Greater and lesser palatine canals Pterygoid canal
Internal Acoustic Meatus
From the pterygopalatine ganglion postganglionic GVE fibers provide lacrimation of the eyes and mucus secretion of the nasal cavity and oral cavity.
Facial canal
Petrotympanic fissure
Superior salivary and lacrimal nucleus
Chorda tympani
From the submandibular ganglion postganglionic GVE fibers provide salivation in the oral cavity.
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GSA Component of the
 Facial Nerve GSA is responsible for providing: 1. Touch, temperature, and pain sensation from part of the external acoustic meatus via the posterior auricular nerve.
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1. GSA provides touch, temperature, and pain sensation from the external acoustic meatus. Cotton swab
GSA
Touch, temperature, and pain sensation from part of the external acoustic meatus.
Posterior auricular nerve
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Foramen Rotundem
Summary of GSA
Internal Acoustic Meatus
Facial canal
Facial nerve Stylomastoid Foramen
Facial nerve
Touch, temperature, and pain sensation from the external acoustic meatus. Posterior auricular nerve
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Inferior Orbital Fissure
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.