1. The Facial Nerve: Functional Components and Anatomy

2. 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.

3. 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

4. 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.

5. 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)

6. 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.

7. The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic meatus.

8. Within the internal acoustic meatus the facial nerve enters the facial canal.

9. 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.

10. The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.

11. 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.

12. The descending portion of the facial nerve continues into the parotid region by way of the stylomastoid foramen.

13. Functional components of the Facial Nerve (CN VII)1.
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. 2. 3. 4. 5.

14. SVE Component of the Facial Nerve
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)
2. Posterior auricular muscle -- posterior movement of pinna
3. Stylohyoid muscle -- elevates hyoid bone
4. Posterior belly of digastric -- elevates hyoid bone, depresses mandible
5. Muscles of facial expression -- blinking, smiling, frowning, facial movements

15. \ 1. The Stapedius muscle dampens movement of the ossicles
When a loud noise is heard by the ear:
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting into the middle ear via the stapedial nerve.
In the middle ear the stapedius muscle dampens movement of the ossicles, protecting the inner ear from damage from loud noises.

16. \ 2. The Posterior Auricular nerve innervates the posterior
auricular muscle, pulling the pinna posteriorly.
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the posterior auricular nerve branches from the facial nerve and via the SVE component of the posterior auricular nerve the posterior auricular muscle pulls the pinna posteriorly.

17. \ 3. The Stylohyoid muscle elevates the hyoid bone
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the stylohyoid branch of the facial nerve innervates the stylohyoid muscle.
The Stylohyoid muscle elevates the hyoid bone.

18. \ 4. The Posterior belly of digastric muscle elevates the hyoid bone
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the Posterior belly of the digastric branch of the facial nerve innervates the posterior belly of the digastric muscle.
The posterior belly of digastric muscle elevates the hyoid bone

19. 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
Buccal branch innervates
buccinator--tenses cheek
Mandibular branch innervates depressor angularis oris--frowning
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.

20. 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. \
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the temporal and zygomatic branches of the facial nerve innervate the orbicularis oculi muscle.
Contraction of orbicularis oculi causes the eyelid to close.

21. B. The zygomatic and buccal branches of the facial nerve innervate the ipsilateral zygomaticus major muscle, the main muscle responsible for smiling. \
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the zygomatic and buccal branches of the facial nerve innervate the zygomaticus major muscle.
Contraction of the zygomaticus major muscle causes smiling.

22. 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 sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the buccal branch of the facial nerve innervates the buccinator muscle.
Contraction of the buccinator muscle causes tensing of the cheek which helps position food within the occusal plane for chewing

23. D. The mandibular and buccal branches of the facial nerve innervate the ipsilateral depressor angularis oris muscle, a muscle responsible for frowning. \
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the mandibular branch of the facial nerve innervates the depressor angularis oris muscle.
Contraction of the depressor angularis oris muscle causes frowning.

24. E. The cervical branch of the facial nerve innervates the platysma muscle, a muscle partly responsible for depressing the mandible. \
SVE sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the cervical branch of the facial nerve innervates the platysma muscle.
Contraction of the platysma muscle results in depression of the mandible.

25. 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 sends a signal from the motor nucleus of the facial nerve, through the internal acoustic meatus, traveling through the facial canal until exiting at the stylomastoid foramen.
After exiting the stylomastoid foramen the cervical branch of the facial nerve innervates the platysma muscle.
Contraction of the platysma muscle causes the skin of the anterior neck to tighten.

26. Summary of SVE
1. A nerve signal is transmitted from the facial nucleus, through the internal acoustic meatus, to the middle ear where stapedius muscle contraction dampens movement of the ossicles.
2. A nerve signal is transmitted from the facial nucleus, through the internal acoustic meatus, through the stylomastoid foramen to the temporal (orbicularis oculi closes eyelids), zygomatic (zygomaticus major muscle partly responsible for smiling), buccal (buccinator tenses cheek), mandibular (depressor angularis oris responsible for frowning), and cervical (platysma helps lower mandible and tightens skin of neck) branches of the facial nerve.
3. A nerve signal is transmitted from the facial nucleus, through the internal acoustic meatus, through the stylomastoid foramen, to the posterior belly of the digastric muscle, which elevates the hyoid bone.
4. A nerve signal is transmitted from the facial nucleus, through the internal acoustic meatus, through the stylomastoid foramen, to the stylohyoid muscle, which elevates the hyoid bone.
5. A nerve signal is transmitted from the facial nucleus, through the internal acoustic meatus, through the stylomastoid foramen, to the posterior auricular muscle, which is responsible for posterior displacement of the pinna.

27. GVA Component of the Facial Nerve
The next slide demonstrates that GVA is responsible for providing:
Light touch, temperature, and pain sensation from the soft palate via the greater superficial petrosal nerve (GSPN).

28. 1. GVA provides sensation of light touch, temperature, and pain from the soft palate.
When the soft palate encounters an extreme temperature, is touched lightly, or is subject to a painful stimulus:
A nerve signal is sent via the GVA component through the lesser palatine canal. The GVA component then becomes part of the GSPN.
As part of the GSPN the GVA component travels to the lacerate foramen, and then through the hiatus of the canal of the GSPN.
At the geniculate ganglion, the GVA component becomes part of the facial nerve.
The nerve signal travels along the GVA component of the facial nerve and passes through the internal acoustic meatus. After passing through the internal acoustic meatus the nerve signal from the soft palate reaches the brainstem.

29. Summary of GVA
A nerve signal is transmitted through the lesser palatine canal, to the lacerate foramen, through the hiatus of the canal of the greater superficial petrosal nerve, and through the internal acoustic meatus to provide light touch, temperature, and pain from the soft palate.

30. SVA Component of the Facial Nerve
The next two slides demonstrate that SVA is responsible for providing:
Taste from the hard and soft palate via the greater superficial petrosal nerve (GSPN).
Taste from the anterior 2/3 of the tongue via the chorda tympani nerve.

31. 1. SVA provides taste sensation from the hard and soft palate via the GSPN.
When food or drink, such as coffee sweetened with sugar, comes in contact with the hard and soft palate:
A nerve signal is sent via the SVA component through the lesser palatine canal. The SVA component then becomes part of the GSPN.
As part of the GSPN the SVA component travels to the lacerate foramen, and then through the hiatus of the canal of the GSPN.
At the geniculate ganglion, the SVA component becomes part of the facial nerve.
The nerve signal travels along the SVA component of the facial nerve and passes through the internal acoustic meatus. After passing through the internal acoustic meatus the nerve signal from the hard and soft palate reaches the brainstem.

32. 2. SVA provides taste to the anterior 2/3 of the tongue via the chorda tympani nerve.
When a drink or food item, such as a lollipop, comes in contact with the anterior 2/3 of the tongue:
A nerve signal is sent via the SVA component.
Fibers from the SVA component then join with fibers from the GVE component to form the chorda tympani nerve.
The chorda tympani nerve passes through the petrotympanic fissure and across the medial surface of the tympanic membrane.
The chorda tympani nerve fibers then become part of the facial nerve. As part of the facial nerve the SVA fibers pass through the internal acoustic meatus. After passing through the internal acoustic meatus the nerve signal from the anterior 2/3 of the tongue reaches the brainstem.

33. Summary of SVA Pathways
1. A nerve signal is transmitted through the greater and lesser palatine canals, to the lacerate foramen, through the hiatus of the canal of the greater superficial petrosal nerve, and through the internal acoustic meatus to provide taste from the hard and soft palate.
2. A nerve signal is transmitted through the petrotympanic fissure and through the internal acoustic meatus to provide taste from the anterior 2/3 of the tongue.

34. 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

35. 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 fibers send a signal from the lacrimal nucleus, through the internal acoustic meatus. The nerve signal travels along the GVE component of the facial nerve
At the geniculate ganglion the nerve signal travels along preganglionic GVE fibers of the GSPN to the Vidian nerve and to the pterygopalatine ganglion.
From the pterygopalatine ganglion postganglionic GVE fibers carry the nerve signal to cause ipsilateral tearing of the eye, mucus secretions of the nasal cavities, and mucus secretions of the hard and soft palate.

36. 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 sends a signal from the superior salivary nucleus, through the internal acoustic meatus. The nerve signal travels along the GVE component of the facial nerve.
At the point that the chorda tympani nerve branches from the facial nerve the nerve signal travels along preganglionic GVE fibers of the chorda tympani nerve, through the petrotympanic fissure, to the submandibular ganglion.
From the submandibular ganglion postganglionic GVE fibers carry the nerve signal to cause salivation from the submandibular and sublingual glands.

37. Summary of GVE
1. From the superior salivary and lacrimal nucleus a nerve signal is transmitted through the internal acoustic meatus, through the hiatus of the canal of the GSPN, to the lacerate foramen, and through the pterygoid canal to the pterygopalatine ganglion. From the pterygopalatine ganglion postganglionic GVE fibers provide lacrimation of the eyes and mucus secretion of the nasal cavity and oral cavity.
2. From the superior salivary and lacrimal nucleus a nerve signal is transmitted through the internal acoustic meatus and through the petrotympanic fissure to the submandibular ganglion. From the submandibular ganglion postganglionic GVE fibers provide salivation in the oral cavity.

38. 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.

39. 1. GSA provides touch, temperature, and pain sensation from the external acoustic meatus.
When the external acoustic meautus encounters an extreme temperature, is touched, or is subject to a painful stimulus:
A nerve signal is sent via the GSA component of the posterior auricular nerve.
The nerve signal continues to travel along the GSA component as part of the descending portion of the facial nerve and passes through the stylomastoid foramen.
From the stylomastoid foramen the nerve signal continues to travel along the GSA component of the facial nerve and passes through the internal acoustic meatus.
After passing through the internal acoustic meatus the nerve signal from the external acoustic meatus reaches the brainstem.

40. Summary of GSA
A nerve signal is transmitted from the external acoustic meatus, through the stylomastoid foramen, and through the internal acoustic meatus to provide touch, temperature, and pain sensation from the external acoustic meatus.

41. 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.

42. Lesion #1
One effect of a lesion located between the branching of of the stapedial nerve and the branching of the chorda tympani nerve would be paralysis of facial muscles.

43. Lesion #2
Another effect of a lesion located between the branching of the stapedial nerve and the branching of the chorda tympani nerve would be loss of taste of anterior 2/3 of the tongue.

44. Lesion #3
One effect of a lesion located at the stylomastoid foramen would be partial loss of sensation of the external acoustic meatus.

45. Lesion #4
A lesion located between the branching of the GSPN and the branching of the stapedial nerve will spare taste of the hard palate.

46. Lesion #5
A lesion located between the branching of the GSPN and the branching of the stapedial nerve will also spare light touch sensation from the soft palate.

47. Thank You Return to SVE Return to GVA Return to SVA Return to GVE
Return to GSA
Return to Lesions

48. Incorrect The GVA component of the GSPN, which is spared by this lesion, is responsible for providing sensation from the soft palate.
Please try again

49. 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

50. 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

51. Incorrect The GVA component of the GSPN, which is spared by this lesion, is responsible for providing light touch from the soft palate.
Please try again

52. 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

53. Incorrect The GVA component of the GSPN, which is spared by this lesion, is responsible for providing temperature sensation from the soft palate.
Please try again

54. Incorrect The GVA component of the GSPN, which is spared by this lesion, is responsible for providing light touch from the soft palate.
Please try again

55. Incorrect The GVE component of the chorda tympani nerve, which is spared by this lesion, is responsible for providing salivation of the oral cavity.
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56. Incorrect The stapedial nerve (SVE), which is spared by this lesion, is responsible for protecting the ear from increased sensitivity to loud noises.
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57. Incorrect This 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.
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58. Incorrect This lesion will not spare salivation of the oral cavity, which is supplied by the GVE component of the chorda tympani nerve.
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59. Incorrect This lesion will not spare ipsilateral facial expression, which is supplied by the temporal, zygomatic, buccal, mandibular, and cervical branches of the facial nerve (SVE).
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60. Incorrect This lesion will not spare the ability to smile, which is supplied by the zygomatic branch of the facial nerve (SVE).
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61. Incorrect This 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

62. Incorrect This lesion will not spare the ability to smile, which is supplied by the zygomatic branch of the facial nerve (SVE).
Please try again

63. Incorrect This lesion will not spare the ability to protect the ear from loud noises, which is supplied by the stapedial nerve (SVE).
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64. Correct! A lesion here will cause paralysis of facial muscles due to its disruption of the SVE component.
Go back to question 1
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65. 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.
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66. 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.
Go back to question 3
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67. 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.
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68. Correct! A lesion here will spare the sensation of light touch of the soft palate because the GVA component of the GSPN remains intact.
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