The facial muscles, also called craniofacial muscles, are a group of about 20 flat skeletal muscles lying underneath the skin of the face and scalp. Most of them originate from the bones or fibrous structures of the skull and radiate to insert on the skin.
Contrary to the other skeletal muscles they are not surrounded by a fascia, with the exception of the buccinator muscle. The facial muscles are positioned around facial openings (mouth, eye, nose and ear) or stretch across the skull and neck. Thus, these muscles are categorized into several groups;
- Muscles of the mouth (buccolabial group)
- Muscles of the nose (nasal group)
- Muscles of the cranium and neck (epicranial group)
Muscles of the external ear (auricular group)
- Muscles of the eyelid (orbital group)
The specific location and attachments of the facial muscles enable them to produce movements of the face, such as smiling, grinning and frowning. Thus, these muscles are commonly called muscles of facial expression, or mimetic muscles. All of the facial muscles are innervated by the facial nerve (CN VII) and vascularized by the facial artery.
This article will discuss the anatomy of the facial expression muscles and their function.
|Definition and function||A group of muscles originating mainly from the bones of the skull and inserting onto the skin of the face, which produce facial expressions|
|Muscles||Occipitofrontalis, orbicularis oculi, corrugator supercilii, procerus, nasalis, orbicularis oris, levator labii superioris, levator labii superioris alaeque nasi, zygomaticus minor, buccinator, zygomaticus major, levator anguli oris, risorius, depressor anguli oris, depressor labii inferioris, mentalis, platysma|
|Innervation||Facial nerve (CN VII)|
|Blood supply||Facial artery|
- Muscles of the mouth
- Muscles of the nose
- Muscles of the eyelid
- Muscles of the cranium and neck
- Muscles of the external ear
- Clinical notes
Muscles of the mouth
The muscles of the mouth, or buccolabial group of muscles, is a broad group of muscles that form a functional compound that controls the shape and movements of the mouth and lips. There are 11 of these muscles and their functions include:
- Elevating and everting the upper lip: levator labii superioris, levator labii superioris alaeque nasi, risorius, levator anguli oris, zygomaticus major and zygomaticus minor muscles.
- Depressing and everting the lower lip: depressor labii inferioris, depressor anguli oris and mentalis muscles.
- Closing the lips: orbicularis oris muscle.
- Compressing the cheek: buccinator muscle.
The majority of the mouth muscles are connected by a fibromuscular hub onto which their fibers insert. This structure is called the modiolus, it is located at the angles of the mouth and it is primarily formed by the buccinator, orbicularis oris, risorius, depressor anguli oris and zygomaticus major muscles.
Orbicularis oris muscle
The orbicularis oris is a circular composite muscle that surrounds the mouth and forms the majority of lips. It consists of two parts; labial and marginal, with the border between them corresponding to the margin between the lips and the surrounding skin. Both portions originate from the modiolus, which is a fibromuscular structure found on the lateral sides of the mouth where several facial muscles converge. From the modiolus, the fibers of the orbicularis oris course medially to fill the peribucal area.
- The peripheral portion passes medially into the labial areas to insert on the dermis of the lips. In the midline, some of the fibers blend with their respective counterparts, forming the philtrum of the mouth.
- The marginal portion passes from the modiolus on one side to the modiolus on the other side of the mouth. Some of the fibers curl upon themselves, forming the vermilion border, which is the demarcation between the lips and the adjacent skin.
The orbicularis oris is innervated by the buccal and marginal mandibular branches of the facial nerve (CN VII). Its blood supply mainly stems from the superior and inferior labial branches of facial artery, with contributions from the mental and infraorbital branches of maxillary artery and the transverse facial branch of superficial temporal artery.
The function of the orbicularis oris is to produce movements of the lips. A bilateral contraction of the entire muscle brings the lips together and closes the mouth. An isolated contraction of certain parts of the muscle can produce different movements of the mouth, such as lip pouting, puckering, twisting and others. Through these actions, the orbicularis oris facilitates speech and helps produce various facial expressions.
The buccinator muscle forms the muscular basis of the cheek, filling the interval between the maxilla and mandible. It is composed of three parts; superior, inferior and posterior.
- The superior part originates from the alveolar process of maxilla, opposite the three maxillary molar teeth.
- The inferior part originates from the buccinator ridge of mandible, opposite the three mandibular molar teeth.
- The posterior part originates from the anterior margin of the pterygomandibular raphe behind the third mandibular molar.
All three parts of the buccinator converge towards the angle of the mouth and fill the space between the upper and lower jaws. At the angle of the mouth, the fibers of the buccinator blend with other facial muscles, including orbicularis oris, risorius, depressor anguli oris and zygomaticus major, forming the modiolus.
The buccinator is innervated by the buccal branches of the facial nerve (CN VII), and vascularized mainly by the buccal branch of the maxillary artery, with contributions from branches of the facial artery.
The function of the buccinator muscle is to compress the cheek against the molar teeth and prevent them from getting bitten during mastication. It also contributes to keeping the bolus of food central in the oral cavity and preventing it from escaping into the oral vestibule. In addition, the buccinator has an important role in playing wind instruments or whistling, since it allows blowing the air from the inflated vestibule by compressing the cheeks.
To find out more, take a look at the dedicated article for the buccinator muscle.
Levator labii superioris muscle
The levator labii superioris is a short triangular muscle that originates from the zygomatic process of maxilla and maxillary process of zygomatic bone. It courses downwards and medially to attach on the skin and submucosa of the upper lip, blending with other facial muscles that insert at this site.
The levator labii superioris is innervated by the zygomatic and buccal branches of facial nerve (CN VII). Its blood supply is provided by the facial artery and infraorbital branch of the maxillary artery.
The action of the levator labii superioris is to assist other buccolabial muscles to elevate and evert the upper lip, exposing the maxillary teeth and deepening the nasolabial lines. This action is significant in making certain facial expressions, such as smiling, grinning and contempt.
Depressor labii inferioris muscle
The depressor labii inferioris is a short quadrangular muscle found in the chin region. It originates from the oblique line of mandible while being continuous with the labial part of the platysma. The muscle courses superomedially to insert on the skin and submucosa of the lower lip.
Nervous supply to the depressor labii inferioris is provided by the mandibular branch of facial nerve (CN VII). Its blood supply comes from the inferior labial branch of facial artery and mental branch of inferior alveolar artery.
The depressor labii inferioris is the main tractor of the lower lip, responsible for pulling the lower lip inferomedially along with the labial part of platysma.
Find out more details about the depressor labii inferioris in the article below.
Levator labii superioris alaeque nasi muscle
The levator labii superioris alaeque nasi is a slender, strap-like muscle found on both sides of the nose. It originates from the upper part of the frontal process of the maxilla and passes inferolaterally, inserting on the perichondrium and the skin over the major alar cartilage of the nose. Some of the fibers pass into the lateral part of the upper lip and blend with levator labii superioris and orbicularis oris.
The levator labii superioris alaeque nasi is innervated by the zygomatic and buccal
branches of facial nerve (CN VII). Its blood supply stems from the facial artery and the infraorbital branch of the maxillary artery.
The function of the levator labii superioris alaeque nasi is to elevate and evert the upper lip, as well as to elevate, deepen and increase the curvature of the nasolabial furrow.
The mentalis is a short conical muscle located in the chin area. It arises from the incisive fossa of mandible and descends inferiorly to insert on the skin of the chin at the level of the mentolabial sulcus of the mandible.
Nervous supply to the mentalis muscle is brought by the mandibular branch of the facial nerve (CN VII). It is vascularized by the inferior labial branch of facial artery and mental branch of the maxillary artery (via inferior alveolar artery).
The mentalis muscle acts to depress and evert the base of the lower lip, while also creating wrinkles on the skin of the chin. These actions contribute to certain activities such as shaping the lips while drinking, as well as creating facial expressions to convey feelings of sadness, contempt and doubt.
The risorius is a highly variable and inconsistent muscle of the buccolabial group. It arises from several origin points that may include the fascia of the parotid gland, fascia of the masseter and platysma muscles, and occasionally the zygomatic arch. The fibers of the risorius converge medially and course horizontally towards the angles of the mouth, where they blend with other facial muscles to create the modiolus.
The innervation of the risorius stems from the buccal branch of facial nerve (CN VII), and vascularized by the superior labial branch of the facial artery.
The risorius is deemed as the “smiling muscle” since its main function involves pulling the angles of the mouth laterally and superiorly to produce a smile.
Levator anguli oris muscle
The levator anguli oris is a slender, sheet-like muscle that arises from the canine fossa of maxilla. It courses almost vertically inferiorly towards the angle of the mouth to attach on the modiolus, while blending with several other facial muscles.
The levator anguli oris is innervated by the zygomatic and buccal branches of facial nerve (CN VII), while its blood supply is provided by the superior labial branch of facial artery and infraorbital branch of maxillary artery.
As its name suggests, the main function of the levator anguli oris is to elevate the angles of the lips, thereby contributing to producing a smile, together with the risorius, zygomaticus major and minor.
Depressor anguli oris muscle
The depressor anguli oris is a triangular muscle situated lateral to the chin on each side of the face. It arises from the oblique line and mental tubercle of mandible and courses almost vertically upwards to attach at the modiolus.
Nervous supply of the depressor anguli oris stems from the marginal mandibular and buccal branches of facial nerve (CN VII). It is vascularized by the inferior labial branch of the facial artery and the mental branch of the maxillary artery.
The depressor anguli oris acts to depress the angle of the mouth, which contributes to expressing feelings of sadness or anger. In addition, this muscle assists in opening the mouth during speaking or eating.
The zygomaticus major is a thin muscle that arises from the lateral surface of the zygomatic bone and extends diagonally to the angle of the mouth. Here, it contributes to the formation of the modiolus by interlacing with several other facial muscles.
The zygomaticus major is innervated by zygomatic and buccal branches of the facial nerve (CN VII). Its blood supply stems from the superior labial branch of the facial artery.
The function of the zygomaticus major involves elevating and everting the angle of the mouth superolaterally, thereby producing a smile in synergy with other muscles.
The zygomaticus minor, similarly to its major counterpart, arises from the lateral surface of the zygomatic bone and extends diagonally towards the lips. It inserts on the skin of the upper lip, medial to the zygomaticus major.
Innervation of the zygomaticus minor is provided by the zygomatic and buccal branches of facial nerve (CN VII), while its vascular supply stems from the superior labial branch of facial artery.
The zygomaticus minor acts in harmony with other tractors of the upper lip to elevate and evert the upper lip, thereby contributing to a variety of facial expressions such as smiling, frowning or grimacing.
Muscles of the nose
The nasal muscle group includes the nasalis and procerus muscles. These muscles are primarily involved in creating facial expressions, but they also contribute to respiration.
The nasalis is a small muscle found on each side of the dorsum of the nose. According to its point of origin, it consists of two parts; alar and transverse part.
- The alar part is found in the area of the nostrils, originating from the frontal part of the maxilla superior to the incisive fossa and medial to the transverse part of the nasalis. It extends upwards and anteriorly to inserts on the skin of the ala, superior to the lateral crus of major alar cartilage.
- The transverse part is found in the area over the dorsum of the nose. It arises superolateral to the incisive fossa, lateral to the alar part. It passes superomedially to to insert at the dorsum of the nose by blending with its counterpart across the bridge of the nose.
The nasalis muscle is innervated by the buccal branch of facial nerve (CN VII) and vascularized by the superior labial, septal and lateral nasal branches of the facial artery, as well as the infraorbital branch of the maxillary artery.
The function of the nasalis muscle involves compressing the nasal aperture with its transverse part, and dilating the nostrils with its alar part. These actions are notable in creating certain facial expressions such as conveying feelings of anger, but also to enhance deep breathing.
The procerus is a small pyramidal muscle occupying the region of the glabella, found between the eyebrows. It arises from the nasal bone and superior part of the lateral nasal cartilage and extends superiorly in a fan-like manner to insert on the skin over the glabella and the medial ends of the eyebrows.
This muscle is innervated by the temporal, lower zygomatic or buccal branches of facial nerve (CN VII). Its blood supply is derived from the angular and lateral nasal branches of the facial artery.
The procerus acts on its superior attachment to depress the medial ends of the eyebrows and wrinkle the skin over the glabella. This creates a facial expression of frowning to convey emotions of anger or sorrow, or when exposed to bright light or other eye irritants.
Muscles of the eyelid
Orbicularis oculi muscle
The orbitalis muscle is a sphincter-like muscle that encircles the orbit and the periorbital area. It is composed of three parts:
- The orbital part is the most peripheral part overlaying the orbital rim. It arises from the nasal part of the frontal bone, frontal process of maxilla and medial palpebral ligament. Its fibers encircle the orbit and insert to the adjacent soft tissue structures.
- The palpebral part is the central part of the muscle that comprises the eyelids. It arises from the medial palpebral ligament and inserts onto the lateral palpebral ligament
- The deep palpebral (lacrimal) part is the deepest part of the orbicularis oculi situated between the medial palpebral ligament and the lacrimal sac. These fibers pass laterally posterior to the lacrimal sac to insert on the superior and inferior tarsi of eyelids, and the lateral palpebral ligament.
The orbicularis oculi receives innervation from the zygomatic and temporal branches of facial nerve (CN VII) and blood supply from branches of the maxillary, superficial temporal and facial arteries.
The function of the orbicularis oculi depends on which part of the muscle contracts. Contraction of the orbital part pulls the skin of the forehead and cheek towards the nose and tightly closes the eyes, commonly for protective purposes. In turn, the palpebral part exhibits a finer control of the eyelids by closing them gently during blinking or sleeping. Finally, the deep palpebral part pulls the eyelids and lacrimal papillae medially and dilates the lacrimal sac, while compressing the lacrimal gland and ducts. These actions facilitate the flow of tears across the lacrimal apparatus.
Corrugator supercilii muscle
The corrugator supercilii is a slender muscle found deep to the medial end of the eyebrows. It arises from the medial end of the superciliary arch of frontal bone, and extends laterally and slightly superiorly to insert into the skin of the middle part of the eyebrow.
The corrugator supercilii is innervated by the temporal branches of the facial nerve (CN VII), and vascularized by the ophthalmic branch of the internal carotid artery, and the superficial temporal branch of the external carotid artery.
Upon contraction, the corrugator supercilii acts to pull the eyebrows medially and produces vertical wrinkles over the glabella, creating a facial expression of frowning.
Muscles of the cranium and neck
The occipitofrontalis is a wide muscle that overlies the superior surface of the scalp, extending from the eyebrows to the superior nuchal lines of the occipital bones. The muscle consists of an occipital and a frontal part, which are connected by a fibrous sheath called the epicranial aponeurosis (galea aponeurotica). Both the occipital and frontal parts contain a pair of quadrangular muscle heads.
- The frontal part originates from the skin of the eyebrows and the superior parts of the periorbital group of facial muscles. It then courses posterolaterally to blend with the epicranial aponeurosis at the level of the coronal suture of the skull.
- The occipital part arises from the lateral two-thirds of the superior nuchal line of occipital bone and courses superiorly to insert onto the epicranial aponeurosis at the lambdoid suture.
Both parts of the occipitofrontalis are innervated by the facial nerve (CN VII). The frontal part is supplied by the temporal branches, while the occipital part receives innervation from the posterior auricular branch of the facial nerve. The blood supply to the frontal part is derived from the ophthalmic and superficial temporal arteries, while the occipital part is vascularized by the posterior auricular and occipital arteries.
The function of the occipitofrontalis depends on which part of the muscle contracts:
- Frontal part: when its forehead attachment is fixed, the contraction of the frontal part pulls the scalp forwards and wrinkles the forehead, producing a frown. If its aponeurotic attachment is fixed, the frontal belly elevates the eyebrows and skin of the forehead, creating an expression of surprise.
- Occipital part: when its nuchal attachment is fixed, the occipital part retracts the scalp. When its aponeurotic attachment is fixed, this part of the muscle moves the scalp anteriorly.
The platysma is a sheet-like muscle situated within the superficial cervical fascia of the anterior neck. It arises from the skin and fascia of the superior thoracic and shoulder regions and ascends along the anterolateral sides of the neck. The medial fibers of the platysma insert onto the lower border of the mandible and the skin of the lower lip. The lateral fibers of the platysma insert on the skin of the perioral region, where they blend with the several muscles surrounding the mouth and contribute to the formation of the modiolus.
The platysma receives nervous supply from the cervical branch of the facial nerve (CN VII), and blood supply from the submental branch of the facial artery, and suprascapular branch of the thyrocervical trunk.
The functions of the platysma depend on the part of the muscle that contracts. With contraction of the lateral fibers that attach on the modiolus, the platysma can contribute to lowering the corners of the mouth and lower lip, while its medial attachment on the mandible can assist in depressing the mandible and opening the mouth.
Muscles of the external ear
The auricular muscles are thin, fan-shaped muscles that connect the auricle to the scalp, and move the auricle to a certain extent. These muscles include:
- The auricularis anterior, that arises from the lateral border of the epicranial aponeurosis and attaches to the spine of the helix of the auricle.
- The auricularis posterior, that arises from the mastoid process of the temporal bone and inserts into the ponticulus on the eminentia conchae.
- The auricularis superior, that arises from the epicranial aponeurosis and converges into a thin, flat tendon to insert onto the upper part of the auricle.
All auricular muscles are innervated by the branches of the facial nerve; the auricularis anterior and superior are supplied by temporal branches, while the auricularis posterior is supplied by the posterior auricular branch. The blood supply for the auricular muscles is mostly derived from the posterior auricular artery.
Since the auricular muscles are quite rudimentary, their function is mainly insignificant in humans. Most of the movements of the ear produced by these muscles are observed during smiling and yawning, involving pulling the auricle anteriorly, posteriorly or superiorly.
Now you know all about the facial muscles, quiz yourself to reinforce your knowledge! Our facial muscles quizzes and labeled diagrams are the best way to practice.
The inability to move facial muscles is a classic symptom of facial nerve paralysis. Hereby, one can clinically differentiate between a peripheral lesion and central lesion.
- In peripheral facial lesions the facial muscles are completely paralyzed on the affected side. When trying to close the lids the eye rotates upwards exposing the sclera (Bell’s phenomenon).
- In central facial lesions one can still wrinkle the forehead on both sides.
The reason behind this is that the motor branches of the forehead muscles derive from both the ipsi- and contralateral facial nuclei. In both types of facial nerve paralysis speech, chewing and facial expression are severely impaired. Depending on the location of the lesion, the affected patients suffer from additional disturbances of tear and saliva secretion, hearing or taste.
There is a variety of causes for facial nerve paralysis including inflammation (e.g. herpes zoster infection), stroke, petrous bone fracture and tumors (e.g. vestibular schwannoma) but in most cases a definite cause cannot be found (idiopathic facial nerve paralysis, also known as Bell’s palsy). Current studies suggest that infections with the Herpes simplex virus type 1 and other less harmful viruses are behind Bell’s palsy.
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