The muscles of facial expression are a group of about 20 flat skeletal muscles that sit just beneath the skin of your face. Unlike most muscles in your body, which connect one bone to another, these muscles have one end attached to your skull and the other end woven directly into your skin. That unique design is what lets them pull your skin into the shapes we recognize as smiles, frowns, squints, and raised eyebrows.
What Makes These Muscles Different
Most skeletal muscles move bones. Facial expression muscles move skin. Because they insert into the soft tissue of your face rather than into another bone, even a tiny contraction can create a visible change on the surface. This is why facial expressions are so precise and nuanced: you can raise one eyebrow, flare one nostril, or curl just one corner of your mouth.
All of these muscles are controlled by a single nerve, the facial nerve (cranial nerve VII). This nerve exits the skull near your ear and splits into five branches, each responsible for a different zone of your face: the forehead, the area around your eyes, the cheek and nose region, the lower lip and jaw, and the chin and neck. That’s why damage to this one nerve can shut down movement across the entire side of your face.
Muscles Around the Eyes and Forehead
The frontalis is the broad, flat muscle of your forehead. When it contracts, it pulls your eyebrows upward and creates horizontal forehead lines. This is the muscle behind a look of surprise or curiosity.
Surrounding each eye is the orbicularis oculi, a circular muscle that works like a drawstring. Its inner fibers gently close your eyelids during a normal blink, while the outer fibers squeeze tightly for a hard squint or a genuine smile. Those outer fibers are also responsible for crow’s feet, the fan of wrinkles that appears at the corners of your eyes.
Sitting between your eyebrows are two smaller muscles. The corrugator supercilii pulls your eyebrows down and inward, creating the vertical furrows of a frown or a concentrated stare. The procerus, a small muscle running down the bridge of your nose, pulls the skin between your eyebrows downward, adding to that furrowed look. Together with the corrugator, it forms what’s sometimes called the “glabellar complex,” the group of muscles that cosmetic injections most commonly target for frown lines.
Muscles Around the Mouth and Lips
The mouth has the most complex arrangement of facial muscles, which makes sense given how much work it does during speech, eating, and emotional expression.
The orbicularis oris encircles both lips. It’s not a simple ring but a highly complex structure made up of four somewhat independent sections: upper, lower, left, and right. Its deeper fibers run horizontally and compress the lips together, acting as a sphincter to keep food and liquid in your mouth. Its more superficial fibers handle finer movements, including the lip shapes needed for speech. Oblique fibers woven between the horizontal ones push the lips outward, creating the natural pout you see in profile.
The zygomaticus major is the primary muscle of smiling. It runs from your cheekbone down to the corner of your mouth, and when it contracts, it pulls the corner upward and outward. A smaller companion, the zygomaticus minor, attaches slightly higher on the lip and assists with expressions like a sneer or a look of sadness.
Working in the opposite direction, the depressor anguli oris pulls the corners of your mouth downward, creating a frown. The depressor labii inferioris pulls your lower lip straight down, as when you show your bottom teeth. The mentalis, a small muscle at the tip of your chin, pushes the lower lip upward and wrinkles the chin, giving you that pouty or doubtful look.
The buccinator sits deep in your cheek. It compresses the cheek against your teeth, which is essential for chewing and blowing air. It also keeps food from getting stuck between your teeth and cheek while you eat. The levator labii superioris lifts your upper lip, and the levator labii superioris alaeque nasi (one of the longest muscle names in the body) lifts both the upper lip and the side of your nose, producing the expression often described as a snarl or a look of disgust.
Muscles of the Nose, Ear, and Neck
The nasalis covers the bridge and sides of your nose. One part flares your nostrils open during heavy breathing; the other compresses them. It’s a subtle muscle, but you’ll notice it working when someone wrinkles their nose.
Humans still have small muscles around the ears, the auricularis anterior, superior, and posterior, though most people can’t control them voluntarily. In other mammals these muscles rotate the ear toward sounds. In humans, they’re largely vestigial, though some people can learn to wiggle their ears using them.
The platysma is a broad, thin sheet of muscle that stretches from your chest and shoulders up over your neck to your lower jaw. It pulls the corners of your mouth downward and tenses the skin of the neck. You can see it working when someone grimaces or strains. It’s controlled by the cervical branch of the facial nerve, making it technically part of the facial expression group even though it lives in the neck.
How Expressions Use Multiple Muscles Together
No facial expression relies on a single muscle. A genuine smile involves the zygomaticus major pulling the mouth corners up while the orbicularis oculi crinkles the skin around the eyes. A “polite” smile that uses only the mouth muscles and leaves the eyes still is visibly different, which is why researchers sometimes call the real version a Duchenne smile.
Surprise recruits the frontalis to raise the eyebrows and the orbicularis oculi to widen the eyes, while the jaw drops open. Anger draws the corrugator supercilii and procerus together to furrow the brow, tightens the orbicularis oris, and may flare the nasalis. Sadness engages the depressor anguli oris to pull the mouth corners down while the inner part of the frontalis raises the inner eyebrows, creating that characteristic triangular brow shape.
These coordinated patterns are remarkably consistent across cultures, which is part of why facial expressions are such a powerful communication tool. Your face can produce thousands of distinct combinations from just 20 or so muscles.
What Happens When These Muscles Stop Working
Because all the muscles of facial expression are controlled by one nerve, damage to that nerve can be dramatic. Bell’s palsy is the most common example. It causes sudden weakness or paralysis on one side of the face, resulting in a drooping eyebrow, a sagging mouth corner, difficulty closing one eyelid, and drooling from one side. People with Bell’s palsy may also experience facial pain, changes in taste, sensitivity to loud sounds, and excessive tearing in one eye.
Doctors check for Bell’s palsy by testing upper and lower facial muscle movement on both sides of the face, including the forehead, eyelid, and mouth. Because the facial nerve also passes through the middle ear, damage can affect a tiny muscle called the stapedius that normally dampens loud sounds, which explains the noise sensitivity some patients report.
Cosmetic Relevance
Cosmetic injections that temporarily relax facial muscles target very specific members of this group. Frown lines between the eyebrows are treated by relaxing the corrugator supercilii, procerus, and depressor supercilii. Horizontal forehead lines are addressed by targeting the frontalis. Crow’s feet are reduced by treating the outer fibers of the orbicularis oculi. The goal is to weaken just enough muscle activity to smooth wrinkles while preserving natural expression, which requires precise knowledge of where each muscle sits and what it does.