Muscles of Facial Expression – Anatomy Tutorial PART 1


This is a tutorial on the muscles of the face,
so the muscles responsible for facial expression. These muscles are innervated by the seventh
cranial nerve, the facial nerve. So when you’re testing a person’s cranial nerves and you
get to cranial nerve no. 7, you ask them to wrinkle their forehead, to close their eyes
as tightly as they can, to show you their teeth by making them smile and asking them
to puff their cheeks out. This is a crude test of the muscles of facial expression. So the way I’m going to do this tutorial is
that I’m going to start superiorly and work through the various muscle groups in the face
— the orbital muscle group, the nasal muscle group and then the muscles in the oral region. So to begin with looking at the superior muscle
on the face, you can see this muscle here, which is the frontal belly of the occipito-frontalis
muscle. It’s called the ‘occipitofrontalis’ muscle because it consists of two muscle bellies.
You’ve got the occipital muscle belly, so called because it’s on the occipital region
of the skull and you’ve got the frontal belly of the occipitofrontalis. Connecting these two muscle bellies, you’ve
got this flat tendon sheath, this aponeurosis. If you have covered the layers of the scalp,
you’ve been told that the aponeurosis of the occipitofrontalis makes up the third layer
of the scalp. So you’ve got skin, connective tissue, aponeurosis, loose connective tissue
and then the periosteum. So the aponeurosis of the occipitofrontalis is the third layer
of the scalp. So if we just look at the orbital region,
we can see these muscles which surround the eye. This muscle is called the orbicularis
oculi. It acts sort of as a sphincter of the eye. You’ve got an outer part and inner part
to this muscle. So this outer part here is called the orbital
part and it’s responsible for closing the eyelids forcefully. If we just zoom in a little
bit more, you can see the inner part of the orbicularis oculi. This is called the palpable
part. It resides inside the eye and it’s responsible for closing the eyelid gently. So that’s the
orbicularis oculi, this circular muscle responsible for closing the eyelids. So the next muscle is this muscle here, the
corrugator supercilii. It lies just deep to the orbicularis oculi and it draws the eyebrows
medially and downward. There are three muscles associated with the
nasal muscles of the face in the nasal group. So you’ve got the procerus, you’ve got the
nasalis, which consists of a transverse part and then alar part and you’ve got this muscle
in the midline which is called the depressor septi nasi. So the procerus muscle here on either side
originates on the nasal bone and inserts onto the skin of the forehead. This muscle is active
when an individual furrows. These muscles here, the nasalis which consists
of the transverse part and the alar part is responsible for compressing and flaring the
nostrils, the nares. So the transverse part compresses the nostrils and the alar part
of the nasalis helps to flare the nostrils. It opens them out. And this muscle here, the depressor septi
nasi, the name kind of gives away what it does, it depresses the nasal septum. It draws
the nose down inferiorly. It actually inserts onto the nasal septum and it assists the alar
part of the nasalis in widening the nostrils. So those are the three muscles of the nasal
group of the facial muscles — the procerus, the nasalis and the depressor septi nasi. So the next group of muscles is the oral group
of muscles. As you can see, there’s quite a lot of muscles which make up this group.
So if you’re not interested in learning about all those in detail, then I’ll just cover
the two muscles that you need to know, then you can switch off after that. And then if
you’re interested, you can carry on listening to find out about the other muscles. So what you need to know in the oral group
if you only are going to learn two muscles is that there’s this big muscle here, which
forms a circle around the mouth. This is known as the orbicularis oris. So just like you’ve
got the circular muscles around the eyes, the constrictor on the eyes, the orbicularis
oculi, you’ve got the orbicularis oris. In Latin, oculus is an eye and os oris is
a mouth. So orifice, oris help you to remember that. So orbicularis oris circle the mouth.
It’s a circular muscle which circles the mouth. And you can kind of guess what the function
is. When it contracts, it narrows the mouth and closes the lips. So you get this pursing
action, which you get when you’re whistling. That’s brought about by this muscle, the orbicularis
oris. And the other muscle you’ll need to know,
which lies deep to these muscles here is the…