FACIAL (VII) NERVE
- The facial nerve is the seventh cranial nerve.
- Mixed nerve consists of a motor and a sensory root.
- Sensory part is frequently described under the name of nervous intermedius (nerve of Wrisberg or pas intermedii of Wrisberg).
- It emerges from the brainstem between the pons and the medulla.
- It controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity.
- It also supplies preganglionic parasympathetic fibers to several head and neck ganglia.
- It is developmentally derived from the second pharyngeal arch.
PATHWAY OF FACIAL NERVE:
l l l l
MOTOR/BRACHIOMOTOR SUPERIOR SALIVATORY (PARSYMPATHETIC) LACRIMATORY(PARASYMPATHETIC) NUCLEUS OF TRACTUS SOLITARUS
MOTOR ROOT SENSORY ROOT OR NERVUS INTERMEDIUS (2 roots attached medial to 8th C.N. TO PONS)
l_ (laterally & forward )______________________________l
INTERNAL ACOUSTIC MEATUS
(here motor lies in groove with sensory root intervening; accompined by labyrinthine vessel)
TRUNK( MOTOR+ SENSORY ROOT at fundus of meatus)
PETROUS PART OF TEMPORAL BONE
l( in Facial canal)
LABYRINTHINE SEGMENT(ends at genu 1st bend)
GENICULATE GANGLION (sensory nerve bodies) → GREATER SUPERFICIAL PETROSAL NERVE
TYMPANIC SEGMENT(in tympanic cavity , medial to incus, ends at 2ndbend)
l→ NERVE TO STAPEDIUS
l→ CHORDA TYMPANI→l
MASTOID SEGMENT BONY l CANAL(in posterio medial wall of middle ear)
l MIDDLE l EAR
STYLOMASTOID FORAMEN PTERGOTYMlPANIC FISSURE
l→ AURICULOTEMPORAL INFRATEMlPORAL FOSSA
l→ DIGASTRIC LINGUAL/ NERVE \
l→ STYLOHYOID SUBMANDIBULARlGANGLION ANT. 2/3 OF TONGUE
PAROTID GLAND SUBMANDIBULAR & SUBLINGUAL GLAND
___________________________l(splits into 5 branches)_____________
l l l l l
TEMPORAL ZYGOMATIC BUCCAL MARGINAL MANDIBULAR CERVICAL
BRANCHES OF FACIAL NERVE:
- GREATER PETROSAL NERVE
- NERVE TO STAPEDIUS
- CHORDA TYMPANI
- EXTRACRANIAL: The arrangement of Branches of Facial nerve after exiting from Parotid gland is given the name asPes Anserinus
- TERMINAL BRANCHES
- MARGINAL MANDIBULAR
forms part of a chain of nerves that innervate the lacrimal gland & mucosal glands of the nose, palate, and pharynx.
|NERVE TO STAPEDIUS||stapedius muscle||Helps muscle to damp excessive vibration on stapes|
||controls movements of the scalp muscles which it supplies around the ear|
|DIGASTRIC||Posterior belly of digastric muscle||motor function|
|STYLOHYOID||Stylohyoid muscle||motor function|
|ZYGOMATIC||Orbicularis oculi||facial expression|
|MARGINAL MANDIBULAR||Muscles of lower lip & chin||Motor function|
BLOOD SUPPLY OF FACIAL NERVE:
- The facial nerve gets it’s blood supply from 4 vessels:
- Anterior inferior cerebellar artery – at the cerebellopontine angle
- Labyrinthine artery (branch of anterior inferior cerebellar artery) – within internal acoustic meatus
- Superficial petrosal artery (branch of middle meningeal artery) – geniculate ganglion and nearby parts
- Stylomastoid artery (branch of posterior auricular artery) – mastoid segment
- The arteries form a external plexus lying within the epineurium and an internal plexus which in intraneural.
- Venous drainage is from Venae comitantes of superficial petrosal and stylomastoid arteries.
- Terminal branches of facial nerve are temporal, zygomatic, buccal, marginal mandibular & cervical
- Branch of facial nerve passing through pterygotympanic fissure is chorda tympani
- The arrangement of Branches of Facial nerve after exiting from Parotid gland is given the name as Pes Anserinus
- Facial nerve is developmentally derived from the second pharyngeal arch
- Chorda tympani is a branch of facial nerve
- chorda tympani joins lingual nerve to supply submandibular gland and tongue
- chorda tympani carries secretomotor fibers to submandibular & sublingual gland
- Chorda tympani branch of facial nerve carries taste sensation from anterior 2/3rd of tongue
- Blood supply of facial nerve is by Anterior inferior cerebellar artery,Labyrinthine artery, Superficial petrosal artery, Stylomastoid artery
- The terminal branches of facial nerve are Temporal, Zygomatic, Buccal, Marginal mandibular & cervical
- Facial nerve supplies lacrimal, mucosal ,sublingual , submandibular glands but not parotid
- The muscles supplied by facial nerve include all muscles of face, scalp, auricle, eyelid, around mouth, neck
- The intracranial branches of facial nerve are greater petrosal, stapedius, chorda tympani
- All the muscles of the face are supplied by facial nerve except levator palpebrae superioris
- Posterior belly of digastric is supplied by facial nerve
- Greater petrosal nerve is the First branch of facial nerve.
- stapedius is supplied by facial nerve