All right it's time to go through
the skeletal muscles in the body that
we're responsible for knowing. There are
over 600 muscles, of course we're not
going to go through 600, just going
through many of the prime movers in the
body, I'm guessing maybe 50 or so and for each muscle you'll see a picture of it
on a figure next to it. You're
responsible for labeling, but that's more
lab, in lab we'll be labeling
muscles on pictures for the most part.
You'll see the origin and insertion of
that muscle, although you're not
responsible to regurgitate the origin
and insertion, but we are responsible for
its actions and you'll see the
actions in italics in that muscle so
that's what you should be mindful of
right when we're going through these
muscles. Also look at the groups, like
what are the breathing muscles, what are
the hamstring muscles, what are the
quadricep muscles, what are the rotator
cuff muscles, so grouping muscles and
knowing their actions is kind of the way
to to go through this. All right, the next few
slides will be muscles of facial
expression. So, these are muscles that are
not pulling on bones, but instead pulling
on soft tissue in order to move the soft
tissue of the face to make a facial
expression like a smile or raise
eyebrows or squint, that type of
thing.
So this first muscle is called the epicranius
or occipitofrontalis; and now we're thinking occipital bone and frontal bone, and that's exactly
where this muscle travels from. You'll
see a muscle belly here, frontalis area,
you'll see a muscle belly on the
occipital bone, occipitalis, so that
entire muscle is called the occipitofrontalis. This muscle happens to have a
wide, broad connective tissue sheet that
connects the two muscle bellies, that is
called an aponeurosis, as a sheet of
fibrous tissue here it's like a wide
piece of connective tissue. You'll see
that in the abdomen as well when we get
there, these aponeuroses but it exists in this
first muscle we're going through, so it
moves the scalp, that's the action
that you see in italics here, the action.
it sill pull it forward, it can pull it back
and that allows you to do things like
wrinkle your forehead or raise your
eyebrows. All right, some other muscles of
facial expression, all three of these
muscles, looks like two, but there's a
zygomaticus major and a zygomaticus
minor. There's also a depressor anguli
oris.
Let's explain these, all three of these
muscles will insert onto the corner of
the mouth. The zygomaticus major
and minor will pull up on that corner
because it's origin is on the zygomatic
bone, the the cheekbone. Here's one
muscle, a zygomatic muscle, this is the
major, it's larger, and you can see that
small one that I'm covering with my
pointer here right above it, that's
zygomaticus minor. Both those muscles will pull up and laterally on the
corner of the mouth from either side and
guess what's that's going to do,
raise the lateral corners of the mouth,
well that helps you with your smiling
expression, and just the opposite,
depressor means pulling down, 'oris' is the
muscle term for mouth, instead of oral, we
have oris because muscles tend to end
in 'i-s' and 'u-s' typically, so pulling down
the mouth at an angle, depressor anguli
oris, here it is right here,
it's pulling that corner of the mouth
down at an angle, and doing that
allows you to frown or grimace.
Kind of the opposite of the of the smile.
So these muscles are antagonists of each
other; when one's contracting the
other one is lengthening, and
vice-versa. Alright this is the last slide on
muscles of facial expression and we have
three more to go through. The orbicularis
muscles. There's orison oculi orbicularis would
be a circular muscle which we can see
around the eye, orbicularis oculi which
contracts to close the eye and then
around the mouth
is the orbicularis Oris that contracts
to close the lips. Last on here we have a
buccinator, weird pronunciation. You
might remember in Chapter 1, buccal
region is the cheek area so there's your
"b-u-c-c" for your cheek
except it's pronounced differently here, buccinator is a muscle that's in your
cheek, it's actually your cheek muscle
and you see it right there, buccinator.
I wouldn't really trust this pointer
it's sort of deep in there we'll see a
picture on another slide, will give us a
good view of the buccinator because
most of it's covered by these
other muscles here. But your cheek
muscles, you compress the cheek to say
some words, to whistle, when you're
chewing food you can maneuver the food
in your mouth between your teeth,
that's the action of the the buccinator. So we'll see buccinator again
when we go through the chewing muscles.
Now the proper term for chewing is
mastication, and there are specific muscles
that are involved with mastication
or chewing. So, first on this first slide
we're going to look at the two prime
movers, primary muscles that close
your jaw and we saw in chapter 9, that
jaw closure is called elevation, so which
muscles pull up on the mandible, in
order to close the jaw. Here's the
to the masseter, 'mas' for chewing
mastication. Masseter is the prime mover
of jaw closer. You can see it here, the
origins on, well mostly on the zygomatic
bone, inserts onto the mandible, on
to the body, and the angle, of the
mandible, so when this muscle contracts
or shortens, it's going to elevate the
jaw or close the jaw. Your other
prime mover, two prime movers here to
close the jaw and by the way, that's the
the action, jaw closure or elevation, the
other muscle is temporalis which is a
muscle on the temporal bone.
It's a convergent muscle as you can see
a very broad origin all these fascicles
that all converge
onto a part of the mandible, not the
condyle if you remember the condyle that
forms the TMJ joint, but there's another
process that you can't see because the
masseter is in the way called the
coronoid process you might recall.
All these fibers will insert onto the
coronoid process so when this muscle
contracts the temporalis muscle, it will
pull up on the jaw, by that coronoid process, and the last
slide for your chewing muscles or
muscles of mastication, muscles that
perform this action, which we call
grinding movements, grinding movements is
kind of bringing your jaw, like making it
go side to side. In order to do that we
need pterygoid muscles and there are two
types of pterygoid muscles: there are two
groups I should say, a medial and a
lateral pterygoid muscle, and you see
them right here up top here, we have a
lateral pterygoid, kind of going
downwards, here's your medial pterygoid
and they bring the jaw left and right in
that motion to to help you grind. Your
buccinator, which we've mentioned
earlier which compresses the cheek, now
we can see it real clearly right there's
our cheek muscle, we didn't have a
good picture last time, it could play a
role in chewing some textbooks
don't consider it a chewing muscles some
do but it helps hold food between the
teeth, just like the pterygoids
do so we'll just include it with our
our muscles of mastication.

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