Motor root of facial nerve

The sensory and motor roots of facial nerve emerge from the junction of the pons and medulla oblongata, just medial to the vestibulocochlear nerve, inside the cerebellopontine angle.

The two roots pass through the internal acoustic meatus to enter the facial canal within the petrous temporal bone. They are accompanied by other structures, including the vestibulocochlear nerve and the labyrinthine vessels. Within the facial canal, the motor root of facial nerve combines with its sensory root to form a single facial nerve trunk. Next, the facial nerve exits from the other end of the bony facial canal via the stylomastoid foramen situated in the base of the skull.

                The neurons contained within the motor root of facial nerve comprise of special visceral efferent fibers which originate from the facial motor nucleus situated within the pons. These motor neurons innervate various muscles that arise from the second branchial arch, such as the stapedius muscle (attached to stapes ossicle within middle ear cavity), posterior auricular, occipitalis, stylohyoid and the posterior belly of digastric muscle. Eventually, the special visceral efferent neuronal fibers channelize through the five terminal branches of the facial nerve (temporal, zygomatic, buccal, mandibular and cervical) to innervate numerous muscles of facial expression.