Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, right now, I’m going to be talking about the muscles of facial expression.
So what I’m going to be doing right on this tutorial is to describe the different muscles that you use for facial expression. So when you’re sad, when you’re angry, when you’re happy, you will be certainly using these muscles, the muscles of facial expression.
And they are a group of about 20 flat skeletal muscles that lie under the skin of your face, and they’re responsible, then, for your facial movement.
These muscles are also sometimes referred to as the mimetic muscles.
And most of them will originate from the skull bone, fascia, or from adjacent muscles that they are connected to, and then they will insert either directly in the connective tissue of the skin or facial muscles as well.
Now, the facial muscles are derived from the second pharyngeal arch. And they are innervated by branches of the seventh cranial nerve, also known as the facial nerve.
And contrary to skeleton muscle, the muscles of facial expression are not surrounded by fascia, except the buccinator.
The facial muscles are placed around facial openings like your mouth, nose, eyes, ears, and also stretch around your neck and skull. And as such, they can, then, be studied or learned according to different regions, as we’re going to see here in this tutorial.
And we can divide the muscles of facial expression into different groups. These groups, then, include the oral group, the nasal group, the orbital group, the auricular group, and the ones we find on the calvaria and neck.
And on this tutorial, what I'm going to be doing is going over the different groups and describing the different muscles that we find on each group. But we’re going to only mention the important things about each muscle, mainly their function.
We’re going to start off with this group here that we isolated. This is known as the oral group. And before we go and talk about each muscle, we’re going to list them. And on the oral group, we’re going to find the orbicularis oris, the buccinator, the levator labii superioris, the levator anguli oris, the depressor labii inferioris, the depressor anguli oris, and the next one has an interesting name to pronounce, especially during oral exams in school, this is known as the levator labii superioris alaeque nasi. We also will see the mentalis, the risorius, the zygomaticus major, and the zygomaticus minor.
Let’s start off with this one that we’re highlighting now in green. This is known as the orbicularis oris muscle. And as you can clearly see here, this muscle encircles the mouth. The contraction of the orbicularis oris will close the mouth. It is also functional in pursing and protrusion of the lips—for instance, while whistling.
The next muscle that we’re going to be talking about is seen here, highlighted in green. This is known as the buccinators, which is an important muscle for eating and drinking as well. So during mastication, it is responsible for moving the food in between the dental arches from the oral vestibule, and thereby keeping the food between the cheeks and the teeth.
It is also helping in creating sucking action for example when babies are suckling, and this muscle forms the muscular base of the cheeks, overlying parts of the maxilla and mandible to the angle of the mouth.
The next muscle that we’re going to be highlighting here is known as the levator labii superioris. And the contraction of this muscle elevates the upper lip.
The next muscle that we’re going to be highlighting here is known as the levator anguli oris. And the contraction of this muscle elevates the angle of the mouth. The action related to the levator anguli is best seen when we smile and the corners of our mouth are pulled upwards.
Next in line is this one that you see here highlighted in green which is known as the depressor labii inferioris. And the contraction of the depressor labii inferioris will pull the lower lip downward.
Now, the next muscle that you see here, highlighted in green, is known as the depressor anguli oris muscle. And this muscle antagonizes the levator anguli oris. When it contracts, it pulls the corner of the mouth downwards. This is best seen, for example, when you make a sad face.
The next muscle that we’re going to be seeing here, highlighted in green, is known as the levator labii superioris alaeque nasi. The contraction of this muscle elevates the upper lip and also dilates your nostrils. You can also see it here from a lateral view.
Next muscle that we’re going to be highlighting here is known as the mentalis. And the mentalis muscle, when you contract it, it will pull the skin of the chin upwards and also protrudes the lower lip. It also forms the furrow between the chin and the lower lip.
Next muscle that you now see, highlighted, is known as the risorius muscle, sometimes referred to as the laughing muscle. It moves the angle of the mouth laterally.
Now, we’re going to be looking at this muscle here known as the zygomaticus major. And this is a large muscle of the zygomatic arch which moves the angle of the mouth upwards and laterally when contracted.
The next muscle that we’re going to be seeing here is known as the zygomaticus minor muscle. And this muscle helps move the upper lip upwards, outwards, and backwards. And you can also see it here laterally.
We are now ready to move on to the next group of muscles, of facial muscles, that you see here, now isolated. This group is known as the nasal group. And the nasal group is comprised of two muscles: the nasalis and the procerus.
Now starting off with the first one on our list, seen here highlighted in green, this is, then, the nasalis. And this muscle is responsible for narrowing or compression of your nostrils. It is comprised of two parts, the transverse part and also an alar part. And we can see it here also from a lateral view.
Next one on the list is this one that you see here, highlighted in green, known as the procerus muscle. And this muscle, when contracted, wrinkles the skin on the bridge of your nose. It assists in the flaring of the nostrils and can be seen functioning when you make an angry face. And you can also see the muscle here from a lateral view.
Now, this is a small group, like the next one that we’re going to talk about. This is known as the orbital group. And the orbital group is comprised of these two muscles: the orbicularis oculi and the corrugator supercilii.
Let’s start with the first one on this list that you see now, highlighted in green. This is the orbicularis oculi. And the orbicularis oculi encircles your eyes, and this muscle consists of three parts: an orbital part, a lacrimal part, and a palpebral part.
Now, if we take a closer look here at the different parts of the orbicularis oculi, the orbital part tightly contracts the skin around the eye allowing, first of all, closure of the eyelids. While, then, the lacrimal part, when contracted, aids in the flow of tears by acting on the lacrimal sac.
Now, as for the last part, the palpebral part, this one is responsible for the closure of the eyelids gently as is the case when we blink, the palpebral reflex.
Last one on the list that we saw, this is known as the corrugator supercilii. And this muscle functions to wrinkle the eyebrows, drawing the eyebrows medially and inferiorly.
We are now ready to move on to the next group that we see here, isolated. This is known as the auricular group. And the auricular group is comprised by the auricularis anterior, the superior, and also the posterior.
We’re going to start looking at the auricularis anterior, as seen here, highlighted from an anterior view. This muscle is responsible for drawing the auricle forward or your ear forward when it contracts. And you can also see here a better view of this muscle from an anterior or a lateral view of your head.
Now, we’re going to move on to next one on the list. This is the auricularis superior muscle which, in this instance, will then draw the auricle upwards, or it’s going to pull your ears upwards when it contracts. And you can see here as well that this muscle can clearly, when contracting, pull your ear up.
Now, the next one that we saw on the list, this one found a bit more posteriorly, then we will call it the auricularis posterior muscle. And this muscle will, then, draw the auricle posteriorly when contracted.
Now, we’re ready to move on to the last group on this tutorial. This is known as the calvaria and neck group. And this group is comprised of two muscles: the epicranius muscle and the platysma.
Now, the epicranius muscle is a muscle of the calvaria consisting of two parts, the occipitofrontalis and temporoparietalis.
We’re going to take a look now at the occipitofrontalis, as you can see here, highlighted in green. And this muscle has two bellies, a frontal belly which you can clearly see here from an anterior view. But if we were to look from a posterior view, then you can also see the occipital belly. But for facial expression, we’re going to look or focus on the frontal belly of the occipitofrontalis muscle.
The function of this muscle is to wrinkle the forehead and assisting in elevation of your eyebrows. This muscle is found on the forehead and outer surface of the back of your head, where you can, then, find the occipital belly.
Although, I quickly mentioned here, the temporoparietalis muscle has no mimetic function. So, for that reason, we can move on to the next muscle that you now see, highlighted in green. This is known as the platysma. And the platysma is a muscle of the neck found from above the mandible, parotid fascia, to approximately at the height of the second rib or the pectoral fascia.
It is a cutaneous muscle of the neck that functions to wrinkle the skin of the neck.