Facial Nerve (Extra cranial part)

After coming out of the stylomastoid foramen, the Facial nerve runs forwards through the substance of the parotid gland crossing in its course the outer aspects of the styloid process, the retro-mandibular vein and the external carotid artery nd then divides behind the ramus of the mandible into 5 terminal branchs which enter the face by poiercing the antero-medial surface of the parotid gland.

Branches

a)       At its exit from the stylomastoid foramen

          1.       Posterior auricular: (Already described).

          2.       Digastric: Supplies the posterior belly of the Digastric muscle.
            3.         Stylohyoid:  Supplies the Stylohyoid muscle.
b)         On the face:
1.         Temporal branches: 2 of 3 in number. They pass upwards and forwards y crossing the zygomatic arch to reach the side of the head & forehead and supply the following muscles:
          a)       Auricularis anterior and superior.
          b)       Intrinsic muscles of the lateral surface of the auricle.
          c)       Upper part of the Orbicularis oculi.
          d)       Frontalis.
          e)       Corrugator.
2.       Zygomatic branches: 2 in number. They pass forwards above the parotid duct to the lateral angle of the eye across the zygomatic bone and supply the lower part of the Orbicularis oculi, muscles of the nose and muscles between the eye & mouth.
3.       Buccal branches (Superficial & Deep): Run forwards below the parotid duct to the angle of month and supply the muscles of the cheek, Buccinator & Orbicularis oris. Deep branches are upper & lower.       
4.       Marginal mandibular branch: Runs forwards along the body of the mandible; passes deep to the Depressor anguli oris and supplies the Risorius and the muscles of the lower lip and chin.
5.       Cervical branch: Runs downwards behind the angle of the mandible to the neck and supplies the platysma.

N.B.    Free communications are established between the branches of the fcial neree with the great auricular, lesser occipital, transverse cetaceous nerve of thacial nervee neek and with terminal cutaneous branches of the Trigeminal nerve.