Function

The facial nerve is, as its anatomy suggests, multifunctional. Its branches control the muscles of facial expression. In addition, the facial nerve is responsible for tear production from the lacrimal gland and taste sensation from the anterior two-thirds of the tongue.

The fine movements of the muscles of facial expression are used continuously to express emotion. In humans the range of facial expressions is extensive and very well developed. Despite being able to verbally express finite and complex feelings and ideas humans still rely on facial expression as a fundamental method of communication.

Facial nerve functions

Motor function

The facial nerve innervates all the branchiomeric muscles of the second branchial arch, in addition to the posterior belly of the digastric, stylohyoid muscle, and the strapedius muscle of the middle ear.  Voluntary control over the muscles of facial expression is permitted by two types of motor nerve pathway. Firstly, both cerebral hemispheres supply corticonuclear fibres to the muscles of the upper part of the face. Secondly, the lower muscles of the face are supplied only by corticonuclear fibres from the opposite cerebral hemisphere. However there is a separate involuntary pathway that involves fibres from the reticular formation. Innervation from this pathway inducing smiling or laughing, happens automatically in response to emotion.

Function of the muscles of facial expression

Muscle of facial expression Functional movement
Occipitalis Retracts scalp
Frontalis Raises eyebrows
Orbicularis Oculi Closes eyes
Corrugator Supercilii Medially depresses eyebrows and brings them closer together
Procerus Draws skin of forehead down
Nasalis Widens nostrils
Orbicularis Oris Closes and protrudes lips
Levator Labii Superioris Elevates upper lip
Levator Anguli Elevates corners of the mouth when smiling and laughing
Zygomaticus Draws corners of the mouth laterally upwards
Risorius Draws corners of the mouth laterally
Depressor Anguli Oris Depresses corners of the mouth
Depressor Labii Inferioris Depresses lower lip
Mentalis Elevates and protrudes lower lip
Buccinator Compresses cheek
Platysma Depresses mandible and opens mouth

 

Branches of the Facial nerve and the muscles they supply: 

Temporal 

Supplies the auriculares anterior and superior, the frontalis, the orbicularis oculi, and corrugator supercilii. The temporal branch acts as the efferent limb of the corneal reflex.

Zygomatic

Supplies the muscles of the zygomatic arch and orbit.

Buccal

Supplies muscles in the cheek and above the mouth.

Mandibular

Supplies the muscles in the region of the mandible but not the muscles of mastication.

Cervical

Supplies the platysma muscle of the neck.

 Branches of the facial nerve

Sensory function

The sense of taste is referred to as a gustatory sense and the tongue is the main taste organ. Sensations of taste from the anterior two-thirds of the tongue travel through the peripheral axons of nerve cells located in the geniculate ganglion on the facial nerve, before passing via the thalamus to the taste area on the cortex. This anterior portion of the tongue is defined as the area in front of the terminal sulcus and primarily has taste buds that detect sweet, sour and salty flavours.

Parasympathetic function

The facial nerve gives off two separate parasympathetic nerves. The first is the greater petrosal nerve and the second is the chorda tympani. The greater petrosal nerve travels through the middle ear and eventually combines with the deep petrosal nerve to form the nerve of the pterygoid canal.

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Branches of the facial nerve

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