Facial nerve (CN VII)
After working through this study unit you will be able to:
- Describe the structure and functions of the facial nerve.
- Understand the course and parts of the facial nerve.
- List the major branches of the facial nerve.
The facial nerve (CN VII) is a mixed nerve carrying several different types of nerve fibers which allow it to participate in a wide range of functions. These include:
- General somatic afferent (sensory) innervation of the skin around the external acoustic meatus, parts of the auricle and retroauricular/mastoid region.
- Special visceral afferent (taste) sensation from the anterior two-thirds of the tongue.
- General visceral efferent (parasympathetic, or secretomotor) innervation to the lacrimal, submandibular and sublingual glands as well as mucous membranes of the nasal cavity, hard and soft palates.
- Special visceral efferent (branchiomotor) innervation of the muscles of facial expression and scalp, as well as the stapedius, stylohyoid and posterior belly of the digastric muscles.
The facial nerve arises at the cerebellopontine angle as two separate roots. Its motor root is associated with neurons originating in the large motor nucleus of facial nerve, located in the pons. The sensory root contains somatic sensory and visceral sensory (taste) fibers, the cell bodies of which are located in the geniculate ganglion. The central processes of these fibers terminate at the sensory nucleus of trigeminal nerve and nucleus of solitary tract, respectively. Efferent parasympathetic roots (from the superior salivatory nucleus) are also carried within the sensory root, therefore it is not actually completely sensory in composition; hence the term ‘intermediate nerve’ is often used instead.
Along its pathway, the facial nerve can be divided into three different segments: an intracranial (cisternal) part, intratemporal part (enclosed within the temporal bone) and an extracranial part that describes the facial nerve after it emerges from the temporal bone.
To learn in detail about the facial nerve watch the following video.
Take a quiz
Facial nerve causing your stress lines to multiply?! Practice makes perfect, test your knowledge as many times as you need with this quiz.
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Take a final closer look now at each structure in detail.
|Structure and features||
Fibers: General somatic afferent (GSA), special visceral afferent (SVA), general visceral efferent (GVE), special visceral efferent (SVE, branchiomotor)
Origin: Cerebellopontine angle (Motor and sensory (intermediate nerve) roots)
Exits skull: Stylomastoid foramen
Associated nuclei: Motor nucleus of facial nerve, superior salivatory nucleus, nucleus of solitary tract
Associated ganglia: Geniculate ganglion (pterygopalatine ganglion, otic ganglion, submandibular ganglion)
|Parts & branches||
Intracranial: Origin → internal acoustic meatus
Intratemporal: Internal acoustic meatus → stylomastoid foramen
Greater petrosal nerve, nerve to stapedius, chorda tympani
Extracranial: After stylomastoid foramen
Posterior auricular nerve, digastric branch, stylohyoid branch
Parotid plexus: temporal branch, zygomatic branch, buccal branch, marginal mandibular branch, cervical branch
Main: Motor innervation to muscles of facial expression (SVE)
Others: Taste innervation of anterior two-thirds of tongue and palate (SVA), parasympathetic innervation of lacrimal, nasal, palatine and salivary glands (except parotid) (GVE), sensation to parts of auricle and retroauricular region (GSA)