Have you ever worried about wrinkles on your face
or thought about why those poor little facial expression muscles are blamed for the wrinkles
and therefore become this target for injections such as botox and things of that nature?
Well there is something very unique about the facial expression muscles if you compare them
to the muscles in other regions of the body. So in today's video we're going to take a look at those
important anatomical differences thereby answering why facial expression muscles
contribute to wrinkles on the face. So as always, let's get to this anatomical awesomeness!
So before we begin, I have to be polite and introduce Geoffrey the Skeleton. He's going
to help us with certain aspects of this story, and our story begins with talking about how the skin
belongs to the system called the Integumentary System, or the Integument. The Integument is
comprised of three main layers. You've probably heard of some of these layers. The top are the
most superficial layers called the epidermis — that's what you can see on the surface of
everyone. The second layer is the dermis. The third layer down is the hypodermis or referred
to as the subcutaneous layer by some. So those three layers comprise the integument. Now some
people focus on the top two because the epidermis and the dermis really comprise what we call the
"true skin", and then you throw the hypodermis in there and that creates what we call the
whole integumentary system. But again the whole idea about this is, "how does the skin interact
with the muscle tissue in different regions of the body?" So we have this really cool dissection here
called the step dissection. It's called the step dissection because it steps down layer by layer
by layer which is really cool to see. Right here is the epidermis and the dermis we just kept those
two layers together to kind of create what we call our skin here and so we didn't separate those two
superficial layers. Coming down to the third layer this is the hypodermis or the subcutaneous layer
and it's made of adipose tissue as you can see. So one two and three creates the integument.
Going down to the fourth layer people love talking about this stuff this is the deep fascia
or in other words just the fascia, which is the fourth layer down. And underneath that you can see
that relationship of the muscle tissue underneath. So if we were to stick a pin
in anywhere in the human body — your arm, your chest, your leg — anywhere but the face,
and we pushed that pin through you would go through those three layers: the epidermis,
the dermis, the hypodermis first, then you'd hit a fourth layer called the fascia. Then you'd finally
hit the muscle tissue. So come back down and see this here! The muscle tissue is going to slide and
glide underneath the fascia without having much of an interaction with the skin on top of that. That
is going to be extremely different when we compare that to the muscles of the face. One other point
that's really important to talk about when we compare say, limb muscles versus facial expression
muscles, is that this idea that limb muscles and even muscles of the trunk typically attach
from one bone to another. In other words, point a to point b. And when those muscles contract
it brings the bones closer together. So really important point — point a is a bony attachment,
point b is a bony attachment — again we're going to see that a little bit different when it comes
to the muscles of facial expression. So now that we've seen the pattern and how the muscles are and
how they interact with the skin and everywhere else in the body besides the face, let's get
to the pattern of the facial expression muscles. Now fyi, we're gonna use this model the majority
of the time because we need to be respectful for the donors that donated their bodies to science.
I will zoom in and zoom into some really small facial expression muscles at the end of the video
on a real face — probably the smiling muscles because that makes everybody happy. But this
whole idea of how these interact with the skin again is a lot different than say everywhere else.
If we were to stick a pin into the face and go through those layers we'd go through epidermis,
dermis, hypodermis/muscle. That's very different than when we saw down here,
where we saw epidermis, dermis, hypodermis, fascia, then muscle. Imagine if the muscle tissue
was running through the hypodermis or that integumentary system,
it would definitely have to have a greater effect on pulling creases and making wrinkles in the skin
because you're literally running through that skin or that integumentary system. So that's one
major factor that contributes to wrinkles from the facial expression muscles as well as
this next point — Geoffrey doesn't want me to touch his face — we're going to use this one.
Remember when I showed on Geoffrey here we had a muscle attaching from one bone to another bone,
and when it contracted it pulled those two bones together. But both attachment sites were on one
bone and then to another. The facial expression muscles only have one attachment — one end of
the muscle only attaches to the bone, and then the other end traverses more superficial and
attaches into the dermis! So when you actually contract, say the smiling muscle which goes from
this bone here down to the corner of the mouth, it's pulling on skin on the second attachment
site rather than bone. Again, if you're pulling on the skin you're going to create creases!
So there are pros and cons to this whole idea. You can be very expressive with all these facial
expression muscles and some people choose to look at it as a say a sign of aging, some people think
it's a form of you know a sign of character because you're laughing and you're scrunching
your forehead up — we'll let you guys decide on that. But that's why people will inject into the
muscles to create kind of this partial or this temporary paralysis with botox. If those muscles
can't contract they can't tug on certain aspects of the skin and create wrinkles. So as I mentioned
earlier, we'll show a muscle on one of the cadaver dissections that we're currently working on. These
are generous body donors that we're super grateful for. One of the things that I'll
show you is the challenge of dissecting facial expression muscles because of that relationship
between the muscle and the hypodermis, and the dermis. Now the muscle I'm going to show
is a muscle called the Zygomaticus Major. I'm going to show you on the model first here — it's
this muscle here that comes here, and goes down to the corner of the mouth there, running up like so.
Now, it attaches to the Zygomatic Bone, hence the name Zygomaticus, and goes down to the corner of
mouth, when it pulls pulls the corner of the mouth up for smiling. So take a look on the cadaver here
you can see here is the faint muscle coming through as we're removing more and more tissue
here. All the surrounding tissue is essentially the adipose tissue in the skin and again this can
be very challenging to do because you're trying to remove this tissue or the surrounding tissue
without removing the muscle tissue when you're doing a dissection. But again the Zygomaticus
Major coming down from the Zygomatic Bone down to the corner of the mouth to pull up the corner
of the mouth for smiling. Thanks for watching everyone! Hopefully you learned some cool stuff
about how the facial expression muscles differ from muscles throughout the rest of the body.
Continue to smile, engage those muscles, and if you really get sick of them you can always
paralyze them temporarily with some botox injections. Like, subscribe,
leave us some comments on things you guys want to know, and we'll see you during the next video.
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