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nervus facialis
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Cranial nerve VIIsvg
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Cranial nerve VII
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The nerves of the scalp, face, and side of neck
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The is the seventh (VII) of twelve paired
Cranial Nerves . It emerges from the brainstem between the
Pons and the
Medulla , and controls the muscles of facial expression, and
Taste to the anterior two-thirds of the
Tongue . It also supplies preganglionic
Parasympathetic fibers to several head and neck
Ganglia .
The motor part of the facial nerve arises from the
Facial Nerve Nucleus in the
Pons while the sensory part of the facial nerve arises from the
Nervus Intermedius .
The motor part of the facial nerve enters the
Petrous Temporal Bone into the
Internal Auditory Meatus (intimately close to the
Inner Ear ) then runs a tortuous course (including two tight turns) through the
Facial Canal , emerges from the
Stylomastoid Foramen and passes through the
Parotid Gland , where it divides into five major branches. Though it passes through the parotid gland, it does not innervate the gland. This action is the responsibility of cranial nerve IX, the
Glossopharyngeal Nerve .
Inside one of the tight turns in the facial canal, the facial nerve forms the
Geniculate Ganglion .
No other nerve in the body travels such a long distance through a bony canal.
A helpful mnemonic device for remembering the major branches are the phrases: "To
Zanzibar By Motor Car", "Two Zebras Bit My Cat", "Tell Ziggy
Bob Marley Called", "Two Zulus Buggered
Michael Caine " or "Ten Zulus Buggered My Cat"
Its main function is motor control of most of the
Muscles Of Facial Expression . It also innervates the posterior belly of the
Digastric muscle, the
Stylohyoid muscle, and the
Stapedius muscle of the middle
Ear . All of these muscles are striated muscles of
Branchiomeric origin developing from the 2nd pharyngeal arch.
The facial also supplies
Parasympathetic fibers to the
Submandibular Gland and
Sublingual Gland s via
Chorda Tympani and the
Submandibular Ganglion . Parasympathetic innervation serves to increase the flow of saliva from these glands. It also supplies parasympathetic innervation to the nasal mucosa and the
Lacrimal Gland via the
Pterygopalatine Ganglion .
In addition, it receives
Taste sensations from the anterior two-thirds of the
Tongue and sends them to the nucleus of solitary tract. The facial nerve also supplies a small amount of afferent innervation to the
Oropharynx above the
Palatine Tonsil . There is also a small amount of cutaneous sensation carried by the
Nervus Intermedius from the skin in and around the
Auricle (earlobe).
The cell bodies for the facial nerve are grouped in anatomical areas called
Nuclei or
Ganglia . The cell bodies for the afferent nerves are found in the the
Geniculate Ganglion for both taste and general afferent sensation. The cell bodies for muscular efferent nerves are found in the
Facial Motor Nucleus whereas the cell bodies for the parasympathetic efferent nerves are found in the
Superior Salivatory Nucleus .
People may suffer from
Acute Facial Nerve Paralysis , which is usually manifested by facial paralysis.
Bell's Palsy is one type of
Idiopathic acute facial nerve paralysis, which is more accurately described as a multiple cranial nerve ganglionitis that involves the facial nerve, and most likely results from viral infection and also sometimes as a result of Lyme disease.
Voluntary facial movements, such as wrinkling the brow, showing teeth, frowning, closing the eyes tightly (
Lagophthalmos )Kliniska Färdigheter: Informationsutbytet Mellan Patient Och Läkare, LINDGREN, STEFAN, ISBN 91-44-37271-X
, pursing the lips and puffing out the cheeks, all test the facial nerve. There should be no noticeable asymmetry.
In an
Upper Motor Neuron lesion, called
Central Seven , only the lower part of the face on the opposite side will be affected, due to the bilateral control to the upper facial muscles.
Lower Motor Neuron lesions can result in
Bell's Palsy , manifested as both upper and lower facial weakness on the same side of the lesion.
Taste can be tested on the anterior of the tongue, this can be tested with a swab dipped in a flavoured solution, or with electronic stimulation (similar to putting your tongue on a battery).
Facial nerve can also be tested because it controls about 2/3 of the tongue. Try making your finger moist, and dipping it in some sugar, or salt (something sweet/salty) then touch your finger to the back of your tongue. See if you can taste it!
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