The muscles of facial expression (also known as the mimetic muscles) can generally be divided into three main functional categories: orbital, nasal and oral.
These muscles are all innervated by the facialnerve (CN VII).¹
These striated muscles broadly originate from the surface of the skull and insert onto facial skin. Their contraction uniquely pulls on facialskin in order to exhibit various facial expressions.
Orbital Facial Muscles
The orbital facial muscles comprise of three main muscles:²
Occipitofrontalis (frontalis contributes to this functional group)
As well as controlling the movement of the eyelids, these muscles also play a role in protecting the cornea from injury.
The occipitofrontalis muscle comprises of two main sections. These sections include the occipital (located posteriorly) and frontal (located anteriorly) bellies. The frontal belly is the major contributor to facial expression.¹
The occipital belly originates from the occipital bone, as well as the mastoid process of the temporal bone.
The frontal belly originates from the epicranial aponeurosis.¹
The occipital part inserts into the epicranial aponeurosis and the frontal belly inserts into the fascia of the facial muscles surrounding the eyes and the skin above the eyes.²
Contraction of this muscle raises the eyebrows and wrinkles the forehead.
The temporal branch of the facial nerve innervates the frontalis and the posterior auricular branch of the facial nerve innervates the occipitalis.¹
The occipital belly is supplied by the occipital artery and the frontal belly is supplied by the supraorbital and supratrochlear arteries.¹
This muscle comprises of three main sections. These sections include the orbital orbicularis, palpebral orbicularis and lacrimal orbicularis.¹
This muscle originates from the nasal portion of the frontal bone, frontal process of the maxilla, medial palpebral ligament, as well as the lacrimal crest and lacrimal bone.²
The insertion site of this muscle includes the skin overlying the circumference of the orbit, the orbital septum, the temporalaspect of the orbit and inferiorly towards the cheek.
This muscle mainly functions to close the eye.²
The palpebral section functions voluntarily, as well as involuntarily during such actions as in blinking.
The orbital section requires conscious effort.
The lacrimal section controls the tear pump mechanism that filters into the lacrimal sac.
The temporal and zygomatic branches of the facialnerve.¹
Branches of the facial, superficial temporal, maxillary and ophthalmic arteries.¹
This muscle originates at the medial end of the supraorbital ridge.
The skin of the forehead near the eyebrow acts as the insertion site for this muscle.
Contraction of this muscle assists in wrinkling the forehead and drawing the eyebrows downwards and medially to assist in shielding the eyes from bright light.¹
The oral muscles are responsible for the movement of the lips and mouth. This group comprises of the following muscles: orbicularis oris, buccinators, depressor anguli oris,levator anguli oris,risorius,zygomaticus major and minor,levator labii superioris,levator labii superioris alaeque nasi,depressor labii inferioris,mentalis and platysma.²
This sphincter-like muscle is located around the circumference of the mouth.
The medial aspect of the maxilla and mandible and the modiolus.¹
The skin surrounding the lips is the insertion site of the orbicularis oris muscle.¹
The contraction of this muscle puckers the lips and closes the mouth.
The superior and inferior labial branches of the facial artery.¹
The buccinator is located between the maxilla and mandible. The buccinator forms the anterior aspect of the cheek and the lateral aspect of the oral cavity. Several structures penetrate the buccinators, including the parotid duct, molar glands of the cheeks, as well as the buccal branch of the mandibular nerve.
The outer surfaces of the alveolar processes of the mandible and maxilla, and the pterygomandibular raphe.
The orbicularis oris muscle and modiolus act as the insertion site for this muscle.
Contraction of this muscle compresses the cheeks against the teeth (this action is especially useful in mastication and whistling).