Anatomy of Facial Nerve

Otology

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Facial Nerve Anatomy

📌 Quick Facts

Cranial Nerve: VII (7th)
Type: Mixed (motor, sensory, parasympathetic)
Nerve of Second Branchial Arch.
Mnemonic: P to P – from Pons to Pyramid
Sensory Component: Known as Nerve of Wrisberg
Axons: Both myelinated and unmyelinated

🔎 Functional Components of Facial Nerve

The facial nerve has five functional components:

Functional Component	Description	Nucleus of Origin
1. Special Visceral Efferent (Branchial Efferent)	Supplies muscles of facial expression (derived from 2nd branchial arch)	Motor nucleus of facial nerve
2. General Visceral Efferent	Secretomotor to lacrimal, submandibular, sublingual, nasal, and palatal glands	Superior salivatory nucleus
3. Special Visceral Afferent	Taste from anterior 2/3 of tongue (via chorda tympani), and palate (via greater petrosal nerve)	Nucleus of tractus solitarius
4. General Somatic Afferent	Cutaneous sensation (posterior external auditory canal)	Spinal nucleus of trigeminal nerve
5. General Visceral Afferent	Pain sensation from tongue and oropharynx	Unspecified

🧠 Nuclei of Facial Nerve

There are four nuclei associated with the facial nerve:

Nucleus	Function
Motor nucleus of facial nerve	Supplies muscles of facial expression
Superior salivatory nucleus	Secretomotor to glands
Nucleus of tractus solitarius	Taste sensation
Spinal nucleus of CN V	Somatosensory from ear region

🧭 Course of the Facial Nerve

The course is divided into three parts:

Intracranial Part

From pons to internal acoustic meatus
Approx. 24 mm long

Intratemporal Part

From internal acoustic meatus to stylomastoid foramen
Approx. 28–30 mm long
Subdivided into:
- Meatal segment – inside IAM
- Labyrinthine segment – to geniculate ganglion
- Tympanic segment – to second genu
- Mastoid segment – to pyramidal eminence

Extracranial Part

From stylomastoid foramen through parotid gland
Divides into terminal branches

🧠 Cortical Innervation

Muscle Group	Type of Cortical Supply	Clinical Relevance
Upper face (frontalis, orbicularis oculi)	Bilateral	Preserved in supranuclear lesions
Lower face	Contralateral	Affected in supranuclear lesions

🌿 Branches of the Facial Nerve

A. From the Geniculate Ganglion

Greater Superficial Petrosal Nerve
- Secretomotor to lacrimal, nasal, and palatal glands

B. Within the Facial Canal

Nerve to Stapedius
- From second genu → Stapedius muscle
Chorda Tympani
- 5 mm proximal to stylomastoid foramen
- Taste from anterior 2/3 of tongue
- Secretomotor to submandibular and sublingual glands

C. After Stylomastoid Foramen (Neck and Face)

Posterior Auricular Nerve
- Supplies pinna, occipital belly of occipitofrontalis
- Communicates with vagus
Muscular branches
- To stylohyoid and posterior belly of digastric

D. Within Parotid Gland

Divides into:

Temporofacial trunk
Cervicofacial trunk

These give rise to five terminal branches:

Branch	Function
Temporal	Forehead muscles
Zygomatic	Orbicularis oculi
Buccal	Buccinator, upper lip
Marginal Mandibular	Lower lip
Cervical	Platysma

E. Communicating Branches

Joins with auricular branch of vagus nerve
Supplies:
- Concha
- Retroauricular groove
- Posterior meatus
- Outer tympanic membrane

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