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Dr Tim Pearce
If you want to upgrade your injection confidence quickly, the best place to start is with your understanding of facial muscle anatomy. When aesthetic practitioners ask how to feel more certain about their injection placements, the answer always comes back to the same foundation: knowing exactly which muscles you’re treating, where they originate, where they insert, and what happens when you relax them with botulinum toxin.
This systematic review of muscular anatomy works from the forehead down to the neck, covering each muscle you’ll encounter in aesthetic practice whether you’re treating it directly or working around it to avoid unwanted effects.
The frontalis muscle and forehead treatment
The frontalis muscle runs from the occipital bone all the way through to the brow ridge, which is why you’ll sometimes hear it called the occipitofrontalis because of that extensive connection. This muscle elevates the eyebrows, though there’s often a component that pulls the forehead down toward the brow as well, making the interplay between elevation and downward pull something your injection pattern needs to account for.
We treat frontalis with botulinum toxin to eliminate horizontal forehead lines and sometimes to lift the eyebrows in specific cases. Understanding that this muscle has both elevating and depressing components helps explain why injection placement matters so much for achieving balanced results.
The procerus muscle and the glabellar complex
The procerus muscle sits as part of the corrugator complex or the glabellar complex, and this muscle pulls downward. It pulls the forehead down and creates a horizontal line across your nose, which is the most common reason you might treat it in isolation since the treatment helps eliminate that line across the nose. Procerus is sometimes used as part of non-surgical rhinoplasty approaches.
The corrugator supercilii represents the muscle predominantly responsible for the 11s lines that patients complain about. We inject this muscle because it’s the main muscle causing the angry expression or the vertical lines on the forehead, so relaxing it makes patients look more relaxed and happier with fewer wrinkles since that muscle isn’t moving quite as much.
The depressor supercilii and its role
The depressor supercilii crosses the corrugator muscle and is often considered simply a little branch of orbicularis oculi, but it does contribute to frowning. We usually treat it alongside the glabellar complex without even having to think about it because it’s so meshed in with the corrugator supercilii, so we inject it really as part of the frown line treatment and perhaps as a way of causing a small lift to the medial brow.
Understanding orbicularis oculi for crow’s feet
The orbicularis oculi muscle sits as the most superficial muscle in this area, lying on top of the others and being most involved with causing lateral canthal lines. This muscle also narrows the eyes, so when you close your eyes tight it’s orbicularis oculi doing that work. It pulls the eyebrows down, pulls the cheeks up, and creates wrinkles around your eyes.
When you relax this muscle with botulinum toxin, you get the opposite of those effects. You may get a little lift to your eyebrow and you may reduce the lateral canthal lines, though there can be a side effect where the cheek is less elevated during smiling which often isn’t desired but is worth knowing about because that’s how that muscle works.
The levator labii superioris and gummy smiles
Medial to orbicularis oculi sits the longest named muscle in the body: the levator labii superioris alaeque nasi. This muscle elevates the lip directly and also creates the snarl expression where it pulls on your nostril. This muscle is most commonly treated specifically to stop its elevation so that the gums don’t show during a smile, with an injection placed just lateral to the nostril.
Orbicularis oris and the lip flip
The orbicularis oris muscle sits medially in the face as an embryologically complex structure where four muscles come together and form what looks to the untrained eye like a sphincter type muscle, though it really isn’t one. This muscle contracts the upper and lower lip to narrow the mouth, and we use it for speech and expression, whistling, and all those sorts of things you can control.
We often inject orbicularis oris to reduce some of the superficial muscle fiber strength when someone has upper lip lines or lower lip lines. The muscle is increasingly used to add some degree of augmentation to the lip with the lip flip technique. One of the theories with the lip flip is that you’re relaxing the muscle where it inserts into the vermillion border which makes that part of the lip bigger, and you may get a slight increase in resting tone in the muscle that’s superior to that, which is effectively what a pout looks like. Contracting higher up and relaxing lower down creates that pout effect, very subtle but it can work in some people.
The lip depressor muscles
The depressor anguli oris starts the series of lip depressors, working laterally first. This muscle pulls down the corner of the mouth and is treated specifically to cause the opposite effect. As you get older, lost fat and lost resistance to movement can result in a downturn mouth, and if you relax that muscle the opposite can occur. We put roughly two units into each muscle for a small lift to the corners of the mouth.
Medial and deep to that sits the depressor labii muscle, which pulls the lip outwards. Some people have quite a strong muscle here, and you’ll see all of their lower teeth when they’re smiling from that strong lateral pull. That’s a strong depressor labii muscle at work.
The mentalis muscle and chin aesthetics
The mentalis muscle pulls the chin up, starting on the bone in the middle of the chin with fibers going down to meet at the point of the chin where you can often see them creating that little indentation sometimes called an ice pick shape or an orange peel effect on the skin. This muscle fiber pull creates skin indentation, which is one reason why you might treat this muscle.
You might use up to four to six units to reduce the texturing on the chin, but also to help the chin lower down so that the chin remains the low point of the face. A heart-shaped face where the chin is the low point represents a marker of beauty, and botulinum toxin treatment in the mentalis muscle can support that aesthetic goal.
The masseter muscle for facial contouring
The masseter muscle runs from your zygoma and is involved in biting, functioning as the strongest muscle during contraction when you bite. You can feel this muscle very clearly when you bite down, watching it push out laterally in a way that provides a useful test if you’re trying to shrink this muscle since you’ll see exactly where the most lateral point sits.
We treat the masseter when we want to shrink its size to create a more heart-shaped face, which works well in females or in someone with a hypertrophic masseter causing a facial shape that’s less than ideal. You shrink the muscle with injections right into the apex of that muscle. Treating the masseter is sometimes used for people with bruxism, so if you’re unintentionally contracting the muscle often during the night and causing headaches then reducing the strength of the masseter muscle with injections can sometimes solve that problem.
The risorius muscle and smile complications
The risorius muscle sits on the other side of the fat pad above the buccinator muscle, and this muscle originates from the surface of the masseter muscle and contributes to smiling. The main reason we encounter risorius in aesthetic practice is actually as a side effect of treating the masseter muscle. We accidentally relax the risorius muscle and it affects the smile of a patient who wanted jawline slimming but instead got a reduction in their smile, which isn’t a pleasant outcome at all and comes from hitting the origin of risorius just where it attaches to the masseter muscle. You see this muscle most active in faces during a really good laugh when all the muscles are contracting and pulling sideways.
The nasalis muscle and bunny lines
The nasalis muscle causes little lines on the nose, often called bunny lines, and you can treat these quite safely with two to four units on each side. The injection placement should be near the muscle’s origin on the bone rather than chasing it down into the face where it inserts.
The platysma muscle for neck rejuvenation
The platysma muscle represents an interesting structure because it runs all the way from your chest all the way up and then meshes with the SMAS in the face. When you relax the muscle in the neck, it can have in some cases an unexpected benefit of lifting the midface, subtle but there is a small chance that works in some patients.
Treatment also helps you get more definition around the jawline and can help soften vertical lines that develop where the strands of muscle become visible in the neck. These can be improved by relaxing them with botulinum toxin. This muscle requires quite a high dose, using up to 80 units sometimes to relax that whole sheet of muscle, but it does have multiple benefits in the face.
Building systematic anatomical confidence
Facial muscle anatomy is your foundation for confident injecting, with each muscle covered here connecting to your daily practice decisions about where to place injections, how to avoid complications, and what effects to expect. When you understand the origins, insertions, and functions of these muscles, you move from following rote patterns to making strategic treatment choices for each individual patient.
The muscles work together as a system where treating one affects the balance of elevators and depressors across the face. The frontalis elevates while the glabellar complex depresses, and the smile muscles pull in different directions while the depressors work in opposition. Understanding these relationships means understanding how your treatments will impact facial expression and aesthetics in ways that create natural, harmonious results.
Watch the full Aesthetics Mastery Show
How to inject confidently – facial muscles in under 10 mins
Dr Tim says:
“This video breaks down every key facial muscle you need to know to elevate your aesthetic results, from forehead to jawline. In this video, you’ll learn:
✅ How the frontalis and glabella muscles impact brow lift and frown lines
✅ Tricks for elevens lines, lateral canthal lines, and upper lip lines
✅ Techniques to create a subtle lip flip, correct downturn mouths, and shape the chin
✅ How the masseter, risorius, nasalis, and platysma influence jawline slimming, smiling, and neck rejuvenation
✅ Practical injection tips for optimizing outcomes and avoiding unwanted side effects
This is a must-watch for aesthetic injectors who want to elevate their practice with science-backed anatomical precision. If you want to inject smarter, safer, and more confidently, this video is packed with actionable education.”
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Dr Tim Pearce eLearning
Dr Tim Pearce MBChB BSc (Hons) MRCGP founded his eLearning concept in 2016 in order to provide readily accessible BOTOX® and dermal filler online courses for fellow Medical Aesthetics practitioners. His objective was to raise standards within the industry – a principle which remains just as relevant today.
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