Chapter 10 Lecture C Muscles Chest Arms

Chapter 10 Lecture C Muscles Chest Arms


when we think about the superficial muscles
of the thorax the muscles that come to mind are the extrinsic shoulder
muscles and some of these are going to include the ones that are really going
to fix the shoulder girdle in place mostly referring to the scapula those that help
to move the scapula or increase the range of the arm movements and
among some of these muscles included are anterior muscles like the pectoralis
major and pectoralis minor the serratus anterior some of the posterior muscles
include things like the latissimus dorsi trapezius levator scapulae as well as
the rhomboids so let’s pay close
attention to some of the specific movements that are permitted by these
extrinsic muscles and first of all some of those movements are going to include
the elevation and depression of the scapula also rotation is going to be
permitted so rotation of the scapula rotation of
the shoulder joint and medial backward movement and lateral or forward movement
of the scapulae as well as protraction and retraction so when we look at these muscles again
you want to learn them in compartments in groups of muscles kind of like
families of muscles if you will and so there are some important ones to know
that are on the anterior surface and then there are also some that we’re
going to learn on the posterior surface so again you need to watch these two
important a&p flicks the overview of the muscles that act on the shoulder joint
and the muscles that act on the shoulder joint and the humerus as well so let’s concentrate first on the
superficial muscles of the thorax that are going to play a role on the pectoral
girdle and as you recall from chapter 8 pectoral girdle is the shoulder girdle
that involves the scapula and the clavicle so when we first look at the pectoralis
minor muscle the pectoralis minor muscle is going to be important as it works
with the ribs when they are fixed when they are stationary and what it does is
it is going to draw the scapula forward and downward so it moves it in an
inferior direction and then there’s also the serratus anterior and the way that you
can recognize the serratus anterior is that sort of looks like a
serrated knife and you’ll definitely have to know this for your lab practical
as well and you may have to identify it on some of the diagrams for the next
test in here the serratus anterior is going to be
important in that it helps to rotate the scapula so that the inferior angle moves
laterally and upward so rotates the scapula and
allows lateral and upward motion and you don’t need to worry about the
subclavius muscle so we can cross this one out and again as always make sure that you
look at the A&P flicks videos there’s lots of them especially for this part of
the book on the pectoral girdle so our next slide is now showing a
diagram of these muscles it’s found in the table and the muscle
gallery that you have in chapter 10 so we talked about the
sternocleidomastoid muscle make sure you know this one the deltoid muscle is the most
superficial muscle in the shoulder area the pectoralis minor serratus anterior
and what we see on this diagram is on the right side of the diagram we see
inferior views or rather this would be a deeper view not an inferior view excuse me and then on the left side of
the diagram what we’re looking at is the more superficial view so the right side is
deep and the left side is superficial you need to of course know the
pectoralis major as I’m sure you’ve already figured out important for
flexing the humerus close the biceps brachii for elbow flexion so our next
slide here is showing reminding us to watch the A&P flicks for pectoralis
minor and the serratus anterior so again with A&P flicks you’re going to see a
lot of videos there are some of which you don’t need to worry about if they’re
not specific muscles that we have looked at this is the posterior view and on the
posterior view again we can see that the right side is going to be showing deeper
muscles and then on the left side we have more superficial muscles so some of these muscles you are responsible
for are the levator scapulae supraspinatus the infraspinatus teres minor
teres major and left side the highlighted ones the trapezius rhomboid
minor rhomboid major latissimus dorsi and how could i forget the deltoid so let’s look at some of the functions
of the specific muscles the trapezius muscle was mentioned earlier in the
previous lecture and the trapezius muscle is the most superficial muscle
that we would see and it has a very broad structure it’s going to attach all
the way down here at one of the lower thoracic vertebrae it’s going to run all the way up
here to this area which is the scapular spine and it comes all the way up to the
occipital bone where it attaches the trapezius much muscle is going to be
very important in that it helps to actually stabilize raised and retract
the scapula so it stabilizes raises and retracts the
scapula so you’re going to use it anytime that
you are doing shoulder shrugs for example if you’re raising your shoulders
or retracting your scapula pulling it backwards the levator scapulae as its name implies
is important for elevation and it’s going to be important in that it
elevates it also adducts the scapula the rhomboids both the rhomboid minor
and the rhomboid major what is important to know about them is
that they are also going to stabilize the scapula and so you can see that
there are many muscles that are going to play a very important role in the
scapula and all of you many of you know this if you’ve ever had a shoulder
injury there can be lots of muscles that could be damaged and then some of
the other muscles that we see here are also part of the what we call the
rotator cuff muscles these would be things like the
infraspinatus the supraspinatus but before we concentrate on that let’s
talk briefly about the deltoid the deltoid is going to be the prime mover
of arm abduction also sometimes called a b duction remember that abduction is
going to be responsible for removing a limb from the body a good way to remember functions is if a
muscle is located more laterally on the lateral side of the body it’s going to play a role in abduction
but if it’s located on the medial side of the body as in the adductor magnus adductor longus it will play a role in a adduction then we have the latissimus dorsi
which is the prime mover for arm extension we use this muscle if we are
swimming for example if you especially think about the butterfly stroke it’s also going to be medially
rotating the arm at the shoulder so arm extension as well as arm adduction so
this would be the opposite of what the deltoid does the deltoid would be arm abduction so here’s your deltoid arm
abduction whereas down here latissimus dorsi
is arm extension and arm adduction so notice that the latissimus dorsi
its origin is going to be anchored to the lower vertebrae so it’s located more medially so
again this rule fits as far as if its a medial muscle it’s a adduction if
it’s located laterally than it would be abduction so then we have our rotator
cuff muscles these are going to be other muscles that
are actually crossing the shoulder joint and there’s a lot of muscles that are
crossing the shoulder joint you can see from the slide there is nine
total muscles that cross the shoulder joint pretty amazing and some are going
to originate at the scapula but others are going to originate from
the axial skeleton itself so from the vertebrae themselves actions are things
like flexion-extension adduction so quite a large variety of different
actions so three of the prime movers of the arm
are the pectoralis major latissimus dorsi and deltoid two of which
we’ve already talked about but let’s spend some time talking about the
pectoralis major and its function is going to be slightly different than the
pectoralis minor but in this case the pectoralis major is going to be the
prime mover of arm flexion it’s also going to rotate the arm
medially and it’s going to adduct the arm so plays a very significant role
then we have our latissimus dorsi muscle the latissimus dorsi muscle remember is
going to be a powerful adductor and the prime mover of arm extension and arm
adduction so again that adduction is kind of the opposite of the deltoid and
then the deltoid is going to be the primary arm abductor so kind of the opposite of the
latissimus dorsi so again think about where these muscles are located in
relationship to the shoulder joint the pectoralis major is going to be on
the anterior surface whereas latissimus dorsi is on the posterior surface so it
would make sense that the function of the pectoralis major is flexion and
since we have a muscle that is sort of opposing at on the posterior view it
would be extension also the deltoid notice is located remember more on the
lateral surface whereas the latissimus dorsi is more medial so again we see
again two opposites in actions as well we have abduction for the deltoid versus
a deduction for the latissimus dorsi we also have the rotator cuff muscles
and the rotator cuff muscles a good way to remember these there’s a little
memory trick called the sits muscles and silly way that I like to remember this
is that if a major league ball player throws out their rotator cuff then they have to sit out and
they have to go to the minors and hopefully this will help you remember
the muscles in order the SITS and the significance of minor
refers to the minor leagues as far as this pneumonic and the important fact is
that the teres minor is a part of the rotator cuff muscles it’s not the
teres major the teres major along with the coracobrachialis would be
a synergist but they’re not one of the main rotator cuff muscles the rotator
cuff muscles of the ones that are going to help to reinforce the shoulder
scapula and prevent this location or an injury to the muscle so let’s go through some of these
functions here and we’ll start above the scapular spine at the supraspinatus
and this is the one that will initiate abduction or A B duction it’s going to
initiate abduction the infraspinatus which is just below the spinous process
is going to rotate the humerus laterally and then the teres minor is going
to have the same action as the infraspinatus so both of them work
together and then the subscapularis muscle is going to be the chief medial
rotator of the humerus so all of these four muscles are going
to work together to allow for the rotator cuff to actually function
whereas the teres major the teres major is going to extend and
it is going to medially rotate and adduct the humerus so slightly different functions and the
rest of the rotator cuff muscles whereas the coracobrachialis is going to
flex and adduct the humerus our next slide is showing these
particular muscles labeled on the diagram and you do need to know all of
these that are shown on here the deltoid pectoralis major coracobrachialis
triceps brachii biceps brachii brachialis and brachioradialis this is
showing the the posterior view of the infraspinatus teres minor
teres major triceps brachii latissimus dorsi and you do not need know the
anconeus so we can cross that one off of this slide here but let’s look real
quick at the rotator cuff muscles in order so we begin with the supraspinatus it’s called the supraspinatus because it is directly superior to the
scapular spine which is this area right here we have a supraspinatus
infraspinatus and the teres minor and then the subscapularis would be on the
anterior view so these are referring to our specific
rotator cuff muscles the sits muscles so again it’s going to include the
teres minor so supraspinatus infraspinatus teres minor and then the
subscapularis would be on the anterior surface if we were to flip it over and
so on this view go through here and highlight
the main ones you have to know which is again most of them the deltoid pectoralis
major coracobrachialis triceps brachii biceps rachii brachialis
brachioradialis so our next slide is showing much of the same thing just go
through highlight the main ones you need to know again you don’t have to know the
anconeus so we’ll cross this one off so now for the hand the hand looks very
complex but the good news is there’s not a lot of these muscles that you actually
have to know what we’re looking at here is the anterior view so the anterior view would be showing
the flexors and the palm side so the important thing to first remember is
that when someone is standing in correct anatomical position if we’re looking at
the anterior view so their palms are facing us the anterior view has the
flexors whereas on the back side of the arm the
posterior of you would have the extensors so this is a great example of where some
of the muscles nick names are actually named for their specific actions so some that you need to know first of
all would be the pronator teres and the pronator teres is going to pronate
the forearm and this is almost where you sort of
make a claw out of your hand it’s the opposite of supination we then have the
flexor carpi radialis and it is going to be a flexor of the wrist so it flexes
the wrist the other thing is that it abducts the hand so the flexor carpi ulnaris is going to
be the opposite action of the flexor carpi radialis so the flexor carpi
ulnaris is also going to be a flexor it’s also going to flex the wrist but it
is going to adduct the hand so that would be the difference between those
two specific muscles and then we have the palmaris longus and it is going to
tense the skin and faccia of the palm during hand movements
and it is going to be a weak wrist flexor and then the other highlighted
one is the flexor digitorum superficialis and it specifically going
to flex the digits so if we look at this specific muscle we can see that it actually extends to
all of the specific digits so those are the main muscles to know
from this slide you do you have to know some of those extensors but they’re on
the next view that we’ll look at so you need to know the flexor digitorum flexor
carpi ulnaris palmaris longus flexor carpi radialis pronator teres and brachioradialis but you do not have to know the some of the others like the
superficial transverse ligament of the palm the palmar aponeurosis you don’t
have to know the retinaculum pronator quadratus flexor pollicis longus
you will have to know the extensor carpi radialis longus but again this is kind of shown in the
next slide that we are going to look so the extensor carpi radialis longus is
shown here and you’re responsible for but it’s going to show this on another
slide or we’ll talk about it there so you do need to know the biceps brachii the
triceps brachii as well so i’ll go through and highlight those now on our
next slide that we see this is just showing you where the
location of some of the flexors are you’re not responsible for these you do
need to know the flexor carpi ulnaris but on the next slide we have three
important extensors that you need to know the extensor carpi radialis longus
you don’t need to worry about the brevis extensor digitorum and the extensor
carpi ulnaris so these three muscles are going to have approximately the opposite
function that the flexors had the flexors were on the Palmer side and the
extensors are going to be on the opposing side so as you might imagine
the extensor carpi radialis and ulnaris both of these are going to be
extending the wrist the one difference is that based on
their location one will be an abductor and one will be an adductor the one that’s
on the radial side is going to be the abductor so it also abducts the wrist whereas the adductor is going to be on
the ulnar side so it will adduct the wrist that’s the one difference in the
function but all of them are going to extend the wrist so you can kind of group them together
for their major functions our next slide is showing the diagram of
these with the extensor digitorum which was on the previous slide the extensor
carpi radialis longus which again the senses on the radial side it will be
abducting the wrist whereas the one that is found on the
ulnar side the extensor carpi ulnaris is going to be an adductor so it adducts the wrist you don’t have to know the anconeus or the extensor digiti minima or the
extensor indicis so we’ll go ahead and cross those out now the same for the abductor pollicis
longus extensor pollicis brevis extensor pollicis longus as well

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