alright in this video guys were going to
talk about the muscles of the back
alright guys so looking at the trapezius here you
can see the trapezius is a pretty big muscle
its got a descending, transverse, and an ascending
portion of it the trapezius has
generally three functions to help
elevate the scapula extend the neck and
retract the scapula
so again it helps to extend the neck
elevate the scapula and
again retract the scapula alright so thats
the trapezius  muscle a pretty big muscle
here and then if I turn a little bit
here we can see some of these muscles
here this right here if you can look
here all of this is the infraspinatus
all this is the infraspinatus and the
infraspinatus helps to be able to
laterally rotate or externally rotate
at the shoulder joint so if you
look over here you can see another
muscle and this are here is called the
teres minor and the teres minor also does
the same function helps to be able to
laterally rotate or externally rotate at
the shoulder
okay then if you look over here you can
see this muscle right there
this is the teres major the teres major
has three functions one function is to
extend the whole arm at the shoulder
joint the other one is to be able to do
adduction at the shoulder joint and then
to medially rotate the shoulder so
that's his function alright so if we look here
we see this huge muscle right here all
this muscle right here is called the
latissimus dorsi and the
latissimus dorsi has three big functions and
those functions are the exact same as
the teres major so if you know what the teres
major does you know what the latissimus dorsi
does which is extend at the
shoulder joint and also adducts at the
shoulder joint and it does medial
rotation so if you think about it we go
back to those terms again these two
muscles are synergist to one another for
all of those actions but then if you
think about the infraspinatus and the
teres minor they like to externally
rotate are laterally rotate
so these two muscles would be antagonist
to the teres major and latissimus dorsi
because these guys medially rotate
these two guys over here teres minor and
infraspinatus they laterally
rotate alright guys so i know i
mentioned these already the infraspinatus
and teres minor there is two other
muscles that will talk about when we get
to the arm being supraspinatus and
the subscapularis these muscles are
really deep muscles and they make up the
rotator cuff and you can remember that
by SITS : supraspinatus, infraspinatus
teres minor and subscapularis because
that's our rotator cuff muscles now what
we're going to do is we're going to
transition to the left side of the torso
so we can see some more back muscles
alright so here we have the rhomboid so
two parts of it so here's the rhomboids
minor and then this one the rhomboids
major both of these muscles have the
same function they retract the scapula
so they'll pull the scapular back right
so again rhomboids minor here
rhomboids major here and they retract
the scapula then over here we have a
some some muscles called the erector
spinae and there's three groups of them
so you have right here running right
down the midline it was called the spinalis
so you have the spinalis right there
right there next to that you have the
longissimus so you have the longissimus
you got spinalis, then longissimus
then all the way here on the
outside you have the iliocostalis
again one more time spinalis, longissimus
and iliocostalis
these muscles function to be able to
extend the vertebral column so  extend the
neck and to be able to extend the
vertebral column so if you remember the
abdominal muscles all of them except for
the transversus abdominus flex the vertebral column
so if you think about it this guy
extends the vertebral column so the
erector spinae muscles as a group are
antagonists to the abdominal wall
muscles being the rectus abdominis the
internal oblique and the external oblique
for that action
ok if you think about it also extends
the neck so who else extend the neck the
trapezius so those guys are synergist
alright so if we come over here this
muscle your kind of wrapping around here
it's called the serratus posterior
inferior as the serratus posterior
inferior so if you look here we got to
thoracolumbar fascia which is an
aponeurosis so its a  connective tissue
aponeurosis and it's a good origin for the
latissimus dorsi  so if you look
here guys we could see another set of
muscles that i want to talk about which
is right here this is called the
quadratus lumborum and the quadratus
lumborum based upon its position it
helps to be able to kind of extend the
lower back so it can extend the lower
back and actually fixes the ribs from
below so fixated the ribs and extends
the lower back that's our quadratus
lumborum right there alright guys so that
basically gives us all the muscles
for the back that we're going to see on
this model alright so taking another
look at these muscles from a different
muscle model just a different view and if we
look here again we got the trapezius
muscle and it comes all the way down
here remember has the descending has a
transverse and it has an ascending
portion so big big muscle right and
again extend the neck elevate the
scapula and retract the scapula
ok that's the function for the trapezius
pretty big muscle then if you look over
here we have the infraspinatus right
there and infraspinatus does
lateral rotation or external rotation at
the shoulder there's this tiny little
muscle right there and that is the teres
minor and the teres minor also does
lateral rotation at the shoulder so
these two are synergists to one another for
that action but if you look right here
we have the teres major and the teres
major does medial rotation at the
shoulder so then that means that it's an
antagonist to these two muscles it does
extension at the shoulder so it could be
a antagonist to the pectoralis major or
the coracobrachialis and it also does
adduction then if we look down here this
big big muscle right here
this one right here this is called
latissimus dorsi , latissimus dorsi it
basically helps to be able to do the
same function as the teres major so
again if you remember the teres major
does extension of the shoulder abduction
of the shoulder and medial rotation the
latissimus dorsi does all the same
functions so these two are synergists to
each other for those actions if you look
here we have all of this connective
tissue  aponeurosis that we talked
about which again is going to be the
thoracolumbar fascia an origin for the one
of the origins for the latissimus dorsi
then what we're going to do is we're going to
take a look over here on the left side
so if we look over here
what I'm going to do is I'm going to
pull this deltoid muscle off so we can
see some of these deeper layers here so
let's take a look at these guys look
here
number two we have over here this is
called the supraspinatus and it fits
inside the supraspinous fossa and what
it does is it helps to be able to do
what's called abduction or pulling the
humerus the whole arm away from that
shoulder joint so he does abduction at
the shoulder so if you think about it we
just said that the the teres major
does adduction so then these two the
teres major and the supraspinatus are
going to be antagonist to one another
for that action then if we look over
here number three this big chunk of
muscle right here this is the
infraspinatus and we already said what
infraspinatus does it does lateral
rotation at the shoulder joint or
external rotation and then we have
another muscle which is going to be this
guy right here this is called the teres
minor and the teres minor also does
lateral rotation or external rotation at
the shoulder joint right so these two
again are synergists to one another and
then we have the teres major right here
and the teres major he does again what we
said extension at the shoulder joint
adduction at the shoulder joint and
medial rotation at the shoulder joint
and again I I'm might have mentioned
this already but again supraspinatus
infraspinatus teres minor and the
subscapularis which we'll see  its
anterior in the subscapular fossa those
are going to be making up the rotator
cuff which are basically fixators ok
then if you look here we are going to have
these muscles right here these two guys here
these are rhomboids again
rhomboids minor rhomboids major and
these retract the scapula
okay so they're synergist to the
trapezius muscle who also retract the
scapula ok but they would be antagonist
to the serratus anterior and the
pectoralis minor who are designed to
protract the scapula
okay then if we look here we got our
erector spinae muscles
ok these chunks here again from the most
medial to the most lateral we go
spinalis, longissimus, and iliocostalis
and again they extend the neck so they
are synergists to the
splenius capitis and the trapezius for
extension of the neck but they're going
to be antagonist as we already said to
the abdominal wall muscles because they
extend the vertebral column where the
abdominal wall muscles except for the
transversus abdominus they flex the
vertebral column okay and then again we
have the serratus posterior inferior
muscle here i'm gonna turn a little bit
here and we can see that tiny little
muscle group over here called the
quadratus lumborum and again we know
that that helps to extend the lower back
and fix these ribs from below again it
gives us all the muscles that we need to
see here on the back muscle wall
