Logan Steele
The human face has around 20 main facial muscles, also known as craniofacial muscles, that are essential for chewing and making facial expressions. These muscles are striated skeletal muscles that are supplied by the facial nerve (cranial nerve VII). They generally originate from the surface of the skull bone and insert on the skin of the face. The facial muscles can be categorized by their location, including buccolabial muscles in and around the mouth, nasal muscles around the nose, and auricular muscles around the ears. The origin and function of these muscles are crucial to understanding facial treatments and disorders.
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What You'll Learn
Facial muscles originate from the skull bone
The human face has around 30 muscles on each side, depending on how they are counted. These muscles are essential to chewing and making facial expressions. They are called craniofacial muscles and are flat, strap-like muscle sheets with interdigitations to the skin, short or absent tendons, and an absent fascial covering.
Facial muscles are just under the skin (subcutaneous) muscles that control facial expressions. They generally originate from the surface of the skull bone (rarely the fascia) and insert into the skin of the face. When they contract, the skin moves. These muscles also cause wrinkles at right angles to the muscles' action line.
The facial muscles are derived from the second branchial/pharyngeal arch. They, like the branchial arches, originally derive from neural crest cells. In humans, they typically begin forming around the eighth week of embryonic development. Facial muscles are unique because they originate from bones and insert into the dermis, manipulating the skin and soft tissues. In contrast, other skeletal muscles move the bones. Additionally, facial muscles have a higher fast-twitch fibre concentration and fewer mitochondria than other muscles.
The most clinically relevant facial muscles are the frontalis, orbicularis oculi, procerus, corrugator supercilia, and orbicularis oris. The frontalis muscle is a broad, thin, bilateral muscle originating from the galea aponeurotica near the coronal suture and inserting onto the superciliary ridge of the frontal bone. The orbicularis oculi is responsible for closing the eyelids, while the orbicularis oris is a circle of muscle around the mouth that closes or purses the lips. The procerus is a muscle between the eyebrows that can pull them downward and help flare the nostrils.
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Three facial muscles don't originate from facial bones
The human face possesses around 30 muscles on each side, depending on how they are counted. The facial muscles are striated muscles that link the facial skin to the skull bone to perform important daily life functions, such as mastication and emotion expression. The facial muscles produce various movements but are often categorized into facial expression (mimetic) and mastication muscles.
Facial muscles are unique because they originate from bones and insert in the dermis, manipulating the skin and soft tissues. In contrast, other skeletal muscles move the bones. Notably, the orbicularis oculi and zygomaticus major are the fastest-moving muscles in the human body.
Most facial muscles originate from the surface of the skull bone. However, three facial muscles do not originate from the facial bones: the frontalis, risorius, and malaris muscles. The frontalis muscle is a broad, thin, bilateral muscle originating from the galea aponeurotica near the coronal suture and inserting onto the superciliary ridge of the frontal bone. It interdigitates with the fibers of the orbicularis oculi, procerus, and corrugator supercilia. The risorius muscle, on the other hand, is a thin, fan-shaped muscle that originates in the fascia of the masseter muscle and inserts into the skin at the angle of the mouth. It is responsible for producing a smile by pulling the angle of the mouth laterally. Lastly, the malaris muscle, also known as the zygomaticus minor, arises from the lateral surface of the zygomatic bone and extends diagonally towards the lips. It inserts into the skin of the upper lip, just medial to the zygomaticus major muscle.
These three muscles, despite not originating directly from the facial bones, still play crucial roles in facial expressions and movements.
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Facial muscles are derived from neural crest cells
The human face has around 30 muscles on each side, and these muscles are responsible for important daily functions such as mastication and emotional expression. Facial muscles are a group of striated skeletal muscles that are supplied by the facial nerve (cranial nerve VII). They are also called mimetic muscles and are only found in mammals, although they are derived from neural crest cells found in all vertebrates.
Facial muscles are derived from the second branchial/pharyngeal arch, which in turn originates from neural crest cells. Neural crest cells are derived from the neural ectoderm and migrate over long distances to form cartilage, bone, connective tissue, sensory neurons, glia, and pigment cells, among other cell types and tissues. They generate the scaffold upon which the head and face are constructed and are largely responsible for facial shape and variation. The muscles of the face, such as those required for jaw opening and closing, are generated from the mesoderm, as are the endothelial cells that form the majority of the vasculature.
The non-epithelial tissues in the facial region originate from migratory neural crest stem cells and the paraxial mesoderm. Embryonic epidermis and endoderm generate epithelialized structures, including covering tissues, various glands, and epithelial compartments of hair follicles and teeth. The paraxial mesoderm produces progenitors of striated muscles and endothelial cells and forms the vascular tree in the face and head.
Craniofacial development requires the integration of multiple tissue interactions, and neural crest cells play a critical role in this process. They migrate in close association with cranial mesoderm and then define a sharp boundary between neural crest cells and mesodermal muscle progenitor cells. This boundary is important for cell interactions during arch development and subsequent jaw morphogenesis.
In summary, facial muscles are derived from neural crest cells, which are critical for the development and shaping of the face and head. These neural crest cells give rise to various tissues and interact with other cell types to form the complex structures of the face and head.
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Facial muscles are responsible for facial expressions
The human face has around 20 main facial muscles, or craniofacial muscles, that work together to control the parts of our face. They are essential to chewing and making facial expressions. Facial muscles are located throughout the face and can be categorized by general location: buccolabial muscles in and around the mouth; nasal muscles around the nose; epicranial muscles of the forehead, skull, and neck; auricular muscles around the ears; and orbital muscles surrounding the eyes.
Facial muscles are just under the skin (subcutaneous) and control facial expressions. They generally originate from the surface of the skull bone and insert onto the skin of the face. When they contract, the skin moves, and these muscles also cause wrinkles at right angles to the muscles' action line. The facial muscles are supplied by the facial nerve (cranial nerve VII), with each nerve serving one side of the face.
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, depressing and everting the lower lip, closing the lips, and compressing the cheek. The majority of the mouth muscles are connected by a fibromuscular hub onto which their fibers insert.
The orbital group of facial muscles contains two muscles associated with the eye socket. These are the only muscles that can close the eyelids. If the facial nerve becomes damaged, the orbital muscles will cease to function, which can cause the cornea to dry out (exposure keratitis). The lower eyelid droops (ectropion), and lacriminal fluid pools in the lower eyelid and cannot be spread across the eye, resulting in a failure to remove debris and ulceration of the corneal surface.
Facial spasms often occur due to neoplastic growths pressing against CN VII. Blood vessels like the anterior inferior cerebellar artery may also pulsate against the nerve, leading to irritation and increased excitability. Some individuals present with congenital hemifacial spasms, while others have a psychogenic etiology.
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Facial muscles are categorised by location
The first group is the buccolabial muscles, which are found in and around the mouth. These include the buccinator, a thin muscle in the cheek that holds each cheek toward the teeth, and the orbicularis oris, which is the main muscle of the lips. The masseter muscle, which runs from each cheek to each side of the jaw, also falls into this category.
The second group is the nasal muscles, which are found around the nose. These include the levator labii superioris alaeque nasi, which can open the nostrils and lift the upper lip.
The third group is the epicranial muscles, which are found on the forehead, skull, and neck. These include the corrugator supercilii, which is near the eyebrow and enables frowning, and the auricular muscles, which allow some people to move their ears.
The fourth group is the orbital muscles, which are found around the eyes. These include the orbicularis oculi, which surrounds the eye socket and extends into the eyelid, and the zygomaticus major, which is one of the fastest-moving muscles in the human body.
In addition to these four main groups, there are also smaller muscles that play a role in facial expressions, such as the mentalis muscle in the chin area and the lateral pterygoid, which helps with jaw opening.
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Frequently asked questions
Facial muscles are a group of striated skeletal muscles that control facial expressions and are essential for chewing. They are just under the skin and are supplied by the facial nerve (cranial nerve VII).
Most facial muscles originate from the surface of the skull bone and insert into the dermis through the superficial musculoaponeurotic system. However, three facial muscles do not originate from the facial bones: the frontalis, risorius, and malaris muscles.
When the facial muscles cannot receive signals from the brain properly, it can cause a droopy or sagging appearance in the face. In some cases, it may also lead to weakness or paralysis of the facial muscles, which can be temporary or indicate a more serious medical condition.
