Superior limb 1- Pectoral girdle

Superior limb 1- Pectoral girdle


– Hi, guys.
We’re here today to talk about the structures
that we’re going to study in lab we’re dealing
with the superior limb and all the muscles, their attachments,
their bony attachments, and their actions
that they’re responsible for in the upper limb.
We’re gonna kind of organize the content
by who’s being moved, and there are between,
you know, four and six muscles in each section
that we’re gonna look at. I think there’s a total of 24
muscles that we’re gonna know. And having all that information,
like, attachments and actions to know for these muscles might
seem a little overwhelming. The good news is,
most of the attachments you already have identified
on the bones. So if you can create a visual in
your brain for how the muscle, like, where the muscle
actually is, you can probably figure out the bone bump based on
the bone bumps you already know, because you’re a rock star.
All right. So I found this website, and I am super stoked about
this thing because it’s online, so it’s free,
and it has some really nice– it’s a nice summary. Still, like, sorting through,
like, what’s the most important thing
is a little bit challenging, but let’s start
out with the muscles that move the pectoral girdle
which is basically the scapula. And so if a muscle moves the
scapula, it’s actually– like, we think of it
as moving the shoulder. So we have four muscles
that fall into this category, and the first muscle in
this group is pectoralis major. The nice thing about this site
is that it’ll show us an image of pectoralis major, and we can actually
dissect the group– except pec major went away.
That was really lame, because usually they
leave pec major– oh, that’s because I’m
in pec minor land. Because the muscle that we’re studying right now
is pec minor, not pec major. That’s pec major which is
superficial to pec minor. Okay.
Let’s go study pec minor because that’s the one
that actually moves the scapula. Now, pec major doesn’t
move the scapula. It’s not in our group today,
in this group. It’s superior– whatever.
We’ll get there. Pec minor moves the shoulder.
Okay. That should tell you right
away that this is– we’re gonna have to have
some kind of attachment to the scapula. And in fact,
if you look at this, and it might be
a little bit hard to tell, so I’m gonna try to eliminate
some of the other muscles so that you can see
this more clearly. Where are my attachments? I have an attachment to ribs. I also have an attachment to the
scapula at the coracoid process. This is all super
straightforward to you. The other cool thing about this
site is that you can actually– there’s an animation or whatever
that will show you the action. If pec minor contracts, once you know where is,
and then you’re like, cool, ribs, coracoids process. Like, look, it’s right there.
I can totally see it. Once you’ve got that
visual in your brain, then you can look at
that thing and be like, okay, coracoids
process to my ribs. What’s gonna happen
if I shorten that? And you can actually figure out what the action is
without even being told. The bottom line is that
it brings the scapula forward and down and so
it’s kind of a protract medial rotate of this scapula. Little bit hard to describe,
and that’s okay. You– if you can explain– if you can look at
it and visualize what that is and then describe it, you’ll be totally
fine on an exam. Let’s go ahead and fill
this in for pec minor. What was one of my attachments?
Let’s go ahead and call it the– oops– the coracoid process. And what was my
other attachment? I vividly remember dissecting Myra and finding the pec
minor and being like– counting her ribs
and remembering– I don’t remember things like
this very well very often, but seeing that, oh,
my God, there’s pec minor on
ribs three through five, and I totally counted them
and it stuck in my brain. Dissection is pretty amazing. So the action, like,
how are we gonna describe that, it depresses shoulder and keep in mind that I’m saying
it depresses the shoulder, but let’s talk scapula, because it’s actually
depressing the scapula, and it’s kind of
rolling it forward. Rolling forward.
How’s that? I’m sure we can come up
with some better words for that. Okay. The next one we want
to look at it serratus anterior, so let’s go take
a look at that guy. Serratus
anterior has serrated edges on the anterior portion
of the muscle. If you see it right here,
it’s a deep muscle. It wraps all the way around. It attaches to ribs
on the anterior surface, and it gives you
this serrated look. And I say it’s a deep muscle
because it actually– now, this is gonna hurt your brain. It actually rolls around from
the anterior surface about here, it rolls around
to the posterior side of your body
underneath the scapula, and it attaches to the medial
border of the scapula. Now, if that bursts your brain, I totally understand
and can totally identify. Let’s see if it will
show us if we feel like, oh, yeah, that’s– I can
total visualize that. Does it get rid of everything? Look.
There. So can you see– okay. Imagine here’s the acromion
process of my scapula and the coracoid process
of my scapula. So the scapula is on the back
surface here, and you can see there’s
muscle tissue back there. And it literally
slides underneath the scapula and attaches
on the medial border, and that kind of hurts my head. I’m like, really?
That’s a strange thing. The serratus
anterior is a muscle that keeps your scapula
from flying off your back. When you do something
like planks, holy crud, if you did not have serratus
anterior when you were planking, you– your scapulas would,
like, fly off your back
and out into the universe, and that would be a bad thing.
I don’t recommend that. So next time you’re planking,
because that’s always fun, go ahead and give a big
woof woof to your serratus anterior because otherwise
you wouldn’t be able to do it. Let’s summarize. Serratus
anterior is attached to– since here’s our scapula side, let’s do medial
border of scapula. You’re cool with that. And then it also
attaches to ribs, and I’m cool just
calling it ribs. I mean, we’ve got numbers, but
I can’t remember what they are, like, one through eight,
something like that. And the major action
that I care– I mean, there’s lots
of things that it does, but the thing that I want you
know is that it holds scapula– that says scapula,
on back. Some of the actions
that we’re going to do, biceps brachii,
are super straightforward. You’re like, oh, boom,
that’s awesome. Other actions, there’s like
a whole bunch of stuff going on. And if we go back and we
look at serratus anterior, like, look
at all those attachments and look
at all those fiber directions. You can imagine
that the muscle fibers, because of the largeness
of the muscle, we have lots of different
directions for the fibers, which means we’re gonna
have different actions facilitated by one muscle.
And that can– that’s where it can get
a little overwhelming. How about trapezius?
Trapezius is the next one. Trapezius is a muscle that is– it makes up
the shoulder curve here. It attaches all the way
down your spine, like, to the lumber vertebra,
look, to T12. So it goes all the way
down your vertebra. It attaches to your skull, and then it jogs on over
and it attaches to the scapula. It attaches to the acromion
and the spine and the scapula. Now, remember that the acromion on the scapula was attached
to the spine. The spine kind of terminated
laterally in the acromion. You can palpate
your acromion process. And that whole line,
I mean, it’s kind of fun
to palpate yourself and be like, oh, that’s– I’m massaging trapezius
right now. But of course I am.
Anyone’s welcome to– never mind.
All right. Now, the action to trapezius.
Here– like, take a deep breath. This is an example of a muscle that actually
has three main parts, and they have three
different names, and they have three
different actions because of the fiber directions. Okay.
We’re cool with that. Let’s go ahead
and watch the actions. Okay. The upper fibers
totally make sense. The upper fibers are going
to elevate your scapula, and it looks like we have
this upwardly rotate whatever, that’s awesome. But can you visualize that?
Let’s watch it again. We’re elevating,
those guys are shortening. Now, take a guess. What’s gonna happen
with my middle fibers? Look at that? They shorten
and they’re going to a deduct or retract the scapulas. And it does both of them,
and so you do kind of this, like, attention action with those middle fibers
of the trapezius. And then the lower fibers,
what are you gonna expect? You’re gonna expect
a depression of the scapula, and let’s watch that one too.
Isn’t that interesting? So this single
muscle depresses the scapula and I want to say elevates it. Expresses?
No. Not that.
Okay. So let’s go put a list– let’s go put a list
on this thing. Attachment number one, I can never remember
which one it is. We’re going to the– so let’s
do spine of scapula to acromion. Does that work for you? And then let’s do skull
and ribs, like, we’re attaching all
the way down, like, and we’ve even got
some ligaments in there that we’ll call those attaching.
And you know what? Here’s what I’m gonna
say about the action. Let’s just do varies, and that’s because you
can visualize. We’re gonna elevate,
we’re gonna a deduct, and we’re gonna depress, depending on which fibers we’re
talking about. And it’s– you look at the fibers
and you can figure out the action just
by looking at the fibers. You don’t really
have to memorize actions. In fact, I don’t
really recommend it. The last group that we’re gonna
look at that moves the scapula are the rhomboids.
Now, the rhomboids are plural because there’s rhomboid major
and rhomboid minor. And rhomboid minor is superior to rhomboid major
which is inferior to– whatever. The bottom line is we’re going
to consider the rhomboids all together.
If you look– in fact, I don’t think– let’s see if rhomboid
major is next. Look.
I mean, minor. Minor is here and I’m just
gonna– oh, look, this is good. Let’s do it like this,
except I want to go back and do it on the one
that I said I was gonna do. Look.
There’s rhomboid major. There’s rhomboid minor,
superior to it. Rhomboid minor,
they’re basically just– they’re like the same
muscle almost, and they just have two
different names. So rhomboids is cool. You tell me just looking
at it where are we attached? Medial border of the scapula and the vertebra,
and look, it looks like T2
to T5 is rhomboid major, so it looks like T1
and maybe C7 are rhomboid minor. I’m not so worried about that. You should be able
to identify it, and if life got real tough you
could probably figure it out. And what’s
their action gonna be? It’s gonna be another,
like, draw to attention dog pound. There they go.
Nice. I like this one best.
Retract or a deduct the scapula, bring it closer to the midline. And that is the action
of the rhomboid. Okay.
Those guys moved our scapula. How did they move the scapula? They had an attachment
to the scapula. If you don’t attach
to the scapula, you’re not gonna move it.
And that was four muscles and you’re done
with four muscles now. Now we’re gonna move the arm.
What is the arm? What’s the bone
that we would expect to attach to if we’re going
to move the arm? Go ahead and think on that one. Hopefully that is not hard.

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