What is Facial Nerve Anatomy?

What is Facial Nerve Anatomy?


the course of the facial nerve can be divided
into two parts: Intracranial – the course of the nerve through
the cranial cavity, and the cranium itself. Extracranial – the course of the nerve outside
the cranium, through the face and neck. Intracranial
The nerve arises in the pons, an area of the brainstem. It begins as two roots; a large motor root,
and a small sensory root (the part of the facial nerve that arises from the sensory
root is sometimes known as the intermediate nerve). The two roots travel through the internal
acoustic meatus, a 1cm long opening in the petrous part of the temporal bone. Here, they are in very close proximity to
the inner ear. Still within the temporal bone, the roots
leave the internal acoustic meatus, and enter into the facial canal. The canal is a ‘Z’ shaped structure. Within the facial canal, three important events
occur: Firstly the two roots fuse to form the facial
nerve. Next, the nerve forms the geniculate ganglion
(a ganglion is a collection of nerve cell bodies). Lastly, the nerve gives rise to:
Greater petrosal nerve – which then supplies parasympathetic fibres to mucous glands and
lacrimal gland. Nerve to stapedius – which then supplies
motor fibres to stapedius muscle of the middle ear. Chorda tympani – which then supplies special
sensory fibres to the anterior 2/3 tongue and parasympathetic fibres to the submandibular
and sublingual glands. The facial nerve then exits the facial canal
(and the cranium) via the stylomastoid foramen. This is an exit located just posterior to
the styloid process of the temporal bone. Extracranial
After exiting the skull, The first extracranial branch to arise is
the posterior auricular nerve. It provides motor innervation to the some
of the muscles around the ear. Immediately distal to this, motor branches
are sent to the posterior belly of the digastric muscle and to the stylohyoidmuscle. The main trunk of the nerve, now termed the
motor root of the facial nerve, continues anteriorly and inferiorly into the parotid
gland Within the parotid gland, the nerve terminates
by splitting into five branches: Temporal branch – which supplies Temporalis
muscle on face Zygomatic branch – which supplies the zygomatic
Arch Buccal branch – Which supplies the buccal
region Marginal mandibular branch – supplies the
mandibular region Cervical branch – Supplies cervical region
These branches are responsible for innervating the muscles of facial expression.