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