Facial nerve - Origin, Function, Pathway & Branches | Anatomy Tutorial 

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Facial nerve is the 7th cranial nerve. It is a mixed nerve, but predominantly it is motor.
Four nuclei are related to the fibers which travel within the facial nerve:
- Motor nucleus of facial nerve located in pons;
- Superior salivatory nucleus;
- Spinal nucleus of trigeminal nerve;
- Nucleus solitarius.
Upon emerging from the stylomastoid foramen, the facial nerve gives rise to the posterior auricular nerve. This branch runs upward in front of the mastoid process and splits into two branches: an auricular branch which supplies the posterior auricular muscle and an occipital branch which supplies the occipitalis muscle.
Another two small branches are arising from the facial nerve soon after emerging from the stylomastoid foramen. Branch to stylohyoid muscle and branch to posterior belly of digastric muscle.
Within the substance of the parotid gland five major branches are arising from the facial nerve which will innervate all the muscles of facial expression. These branches , from top to bottom are as follows:
The temporal branch
The zygomatic branch
The buccal branch
The marginal mandibular branch
The Cervical branch.
From these branches the most important one is the zygomatic branch which supplies the orbicularis occuli muscle. This muscle closes the eyelids.
An injury to the zygomatic branch would alter the function of the ipsilateral oribularis occuli muscle, the eyelids would be unable to close thus inflammation, dryness, ulceration or even blindness may occur in extreme cases.