in this video we're taking a look at the anatomy of the shoulder joint we're going to look at every bone involved every ligament that holds the joint together we'll take a look at the four muscles of the rotator cuff and what each of those does as well as talk a little bit about the movement of the joint it's a complicated joint with a lot going on but we're going to take it step by step drawing it out in the diagram and there'll be a chance to practice as well so by the end of this video you're going to know the ins and outs of the shoulder joint so without further Ado let's jump to the Whiteboard and get started because there's so many structures we're going to break this up into two diagrams and for our first diagram we're just going to look at the anterior side of the shoulder joint so we're sort of looking at the shoulder like this so we're going to start here with two bones that's going to be the sternum right here as well as the clavicle the clavicle is your collarbone and the sternum is right here in the middle we have the scapula which is this irregular shaped bone it's your shoulder blade and it's got several parts to it three important parts that we're going to label on the scapula the first is the coracoid process and that's going to be this piece of the bone that's sort of sticking out here it sticks out anteriorly or towards the front and we have the acromion which is going to wrap around right here and then sort of come up against the clavicle at that spot and then here on the lateral side of the clavicle we've got this sort of indented part or concave part right here and that's going to be the glenoid fossa or the glenoid cavity so again in the scapula we have the coracoid process right here we have the acromion here and the glenoid cavity a lot of names so far but once we look at the ligaments we'll find that they're actually pretty easy to name if you know the different parts of the scap as well as the other bones involved here so next I'm going to draw the humerus the humerus is the main bone in your arm right here it's got a head at the top which makes the ball of this ball and socket joint so this is the head of the humerus and it's going to articulate with the glenoid cavity right here and these make up the ball and the socket of this ball and socket joint of all the types of joints the ball and socket gives the most degrees of freedom in its movement so if you think about your shoulder you can kind of move your shoulder up and down and back and forward and sort of make circles with it that's because of the nature of this ball and socket joint now that allows a lot of extra freedom but that also means that it's going to need a little bit of extra support compared to maybe some other joints to keep it in place where it needs to be and that's where all the ligaments are going to come in but before we get to that it is a synovial joint which means there's going to be articular cartilage at both sides of this joint where it articulates or moves across each other so right here we've got a ticular cartilage on the head of the humerus and we're going to have articular cartilage as well on the glenoid fossil or glenoid cavity so these two surfaces are going to have the smooth articular cartilage and of course that is to reduce the friction between those two bones so they don't wear on each other being a synovial joint there will also be synovial fluid between those two it's sort of a lubricant that's going to help prevent that articular cartilage from breaking down and further reduce the friction between those two bones all synovial joints have a joint capsule we'll get to that in a minute so that's all the bones involved there's really three main bones here right the scapula the clavicle and the humerus and three important parts of the scapula so far the coracoid acromion and glenoid cavity now to hold all this together we need the ligaments so we're going to start with the ligament between the acromion and the clavicle and that's just going to be dense fibers or dense connective tissue and that's going to be a fibrous joint and fibrous joints don't have much movement so there's not going to be much movement between the acromion and the clavicle the purpose of this is sort of just to hold those two bones together now I love the naming conventions on these they make really long words but they're easy to remember if you remember the two parts of this here we have the acromion and the clavicle so this ligament right here is going to be the acromioclavicular ligament all you're doing is taking the tube bones or parts of the bone in terms of the scapula and putting those two words together to make one really long word one quick naming convention coraco is always going to come first if the coracoid is involved and the clavicle is always going to come last if the clavicle is involved if you remember those two rules the rest of it flows pretty easily so coracoid will always be first in the naming and then clavicle will always be last in the naming the next ligament on the diagram isn't really part of this joint per se but it's the ligament between the sternum and the clavicle so follow our naming convention put the two words together clavicle always comes last this is going to be the Sterno clavicular joint or sternoclavicular ligament up next we have a ligament between the coracoid and the acromion so this will be the coraco acromial ligament and I find these not too hard to remember because basically every part that we've labeled here there's going to be a ligament between those parts if they're close to each other and then you just name them based on the parts up next we have a ligament between the coracoid and the clavicle so of course that would be the coraco clavicular ligament so that's four ligaments so far now let's actually move to the glenohumeral Joint we say shoulder joint oftentimes we're talking about like all of this stuff involved right here but the glenohumeral joint is specifically talking about where the ball and the socket is and what's involved there so if I think about like the acromioclavicular ligament that's not really directly involved with the movement of this joint right here so now we're just going to look at the glenohumeral Joint the ball and socket joint of the shoulder now being a synovial joint there's going to be a joint Capsule that's going to do a couple things it's going to sort of stabilize The Joint a little bit it's also going to hold in all of the synovial fluid that's lubricating The Joint so here's our joint capsule and it's going to just completely wrap around all of that articular cartilage and make this sort of capsule to hold in all that fluid now the joint capsule itself isn't all that strong so it provides some support but it's definitely not going to be enough similarly to the knee right we have the ACL and the PCL and all these ligaments that sort of that give it extra structure because the joint capsule isn't strong enough to provide all the support that it needs so same thing here here's a few more ligaments we need to take a look at there's also going to be a ligament between the humerus and the coracoid process right here so I'm going to draw that one in that's going to be the follow the same naming convention the coraco humeral ligament okay there's three more ligaments that we're going to draw in here they're going to connect the humerus to the glenoid cavity and we've kind of already got that drawn in so these are really sort of an extension or a thickened part of the joint capsule this can provide some extra support I'm going to draw them in right here and as they're drawing them in think about the naming convention that we would have here they're between the humerus and really the glenoid phosphor glenoid cavity so we're just going to call them the glenohumeral ligaments there's three of them and we can just name them using Superior middle and inferior so the superior glenohumeral ligament the middle and then the inferior glenohumeral ligament you're a complicated little guy all right quick recap of this we've got three bones involved the clavicle the scapula and the humerus the scapula has a few important parts that's the acromion the coracoid and the glenoid fossa we've got a whole bunch of ligaments we've got the acromioclavicular ligament the sternoclavicular ligament the corticoacromial ligament the coracoclavicular ligament we have the joint Capsule that's going to surround the head of the humerus and the glenoid cavity that's going to contain synovial fluid there's also articular cartilage on the head and then the fossa and then we have the coraco humeral ligament as well as the three glenohumeral ligaments they're going to provide extra support we're about to move to a second diagram to look at the rotator cuff and all that it does but at the end of the video if you want to review this I'm going to have a blank version of this diagram that you can go through and try to label all the parts to it all right now let's take a look at the rotator cuff muscles to really see where these muscles are located we need to look at the anterior and the posterior parts of this so let's go and draw in our bones of course we've got the clavicle we've got the scapula we're going to draw in a few parts here on the anterior part we've already seen this we've got the main body of the scapula we've got the coracoid we've got the acromion sticking out over here we haven't seen the posterior side of the scapula yet there's gonna be one additional structure that we need to draw on here and that's going to be the spine of the scapula that's this part right here it kind of goes down sort of the middle or across the middle sort of like a spine and it sort of forms into the acromion right here and then of course you have the humerus which is going to articulate with the glenoid fossa of the scapula all right rotator cuff what is it exactly it's a set of four muscles that's special functions with the shoulder joint like a lot of muscles they're going to cause movement but they're also going to be support muscles structural support that's going to hold that joint in place in addition to those other ligaments that we saw our first muscle that we have is the infraspinatus muscle infra meaning below and spinatus meaning the spine so this is literally the muscle under the spine of the scapula the infraspinatus muscle which is on the posterior or the back side of the scapula it's going to pull on the humerus rotating the shoulder back like this next just sort of underneath that or inferior to that is going to be the teres minor muscle you can see that muscle right here and you can also see it peeking out right here on our anterior side of the diagram the teres minor is a synergist with the infraspinatus meaning that they're going to have the same function laterally rotating the humerus so if we have the infraspinatus below the spine we must have the supraspinatus above the spine we can also see that in our anterior diagram back over here if you look at the supraspinatus its Origins here above the spine of the scapula and it's going to follow all the way over here and have an insertion in this part of the humerus when it contracts it's going to work to lift the humerus that's going to be a synergist with the deltoid muscle when the deltoid muscle contracts it's also going to work to lift the humerus like this now a torn rotator cuff is a common injury that happens it can be a sports injury but it can also happen in just kind of regular strenuous use of the shoulder the torn rotator cuff could be any of the four rotator cuff muscles but the most common one is the supraspinatus and it'll tear somewhere here in this dense connective tissue when that happens it can be painful you can lose stability and also some movement in that joint now so there's four muscles so there's one more involved and that's going to be the subscapularis sub meaning under and scapularis meaning scapula so sort of under the scapula or it's on the anterior side of the scapula so here's that subscapularis it's going to originate here on the medial side of the scapula and its insertion is going to be here on the head of the humerus you see kind of a ridge right here in the connective tissue we'll talk about that in just a second now the subscapularis being on the front it's going to work very similarly as the deltoids so when it contracts it's going to pull on the humerus and try to rotate it medially or rotate it anteriorly so subscapularis and pectoralis major those are going to be synergists working to rotate the humerus forward so those are the four rotator cuff muscles we have the infraspinatus and the teres minor which are going to work to rotate the shoulder back we have the supraspinatus which along with the deltoids is going to work to abduct the humerus or extend the shoulder joint and we have the subscapularis which is going to work in conjunction with the pectoralis to rotate the shoulder forward now that we have this drawn let's go over the three primary functions of the rotator cuff muscles the first is stabilization now we kind of talked about this a little bit already but those four muscles are going to wrap around the humerus on the top and the two sides sort of just having like this extra strap on there holding it in place so structure and stabilization is number one the second is called concavity compression so this one's a little bit harder to explain but whenever the deltoids pull up on this without the rotator cuff muscles that's going to lift the head of the humerus up without the rotator cuff muscles that's going to lift the head of the humerus upward and that would actually make it a less efficient movement it would make the deltoids a less efficient lever because instead of just rotating it in place it's going to be lifting up on it and we don't really want that upward lift of the humerus we want it to be held in place and in fact we want it to kind of push in a little bit and that's going to make that rotate a little bit easier so we call that concavity compression the rotator cuff muscles whenever we lift our arm like this it's going to pull the head of the humerus medially so it's going to make that rotation a little bit more easy and efficient that's concavity compression pulls the head in so that we can lift it easier and the third function is just movement which we talked about already we have abducting the arm which the supraspinatus does and then we have rotation which the infraspinatus teres minor and subscapularis do that's terminology y'all it's a lot okay next we've got one more muscle I want to draw on here and that's going to be the biceps brachii this is sort of involved in the shoulder joint it's not one of the main muscles you think about when you think about moving the shoulder joint but it's directly involved in the shoulder joint and anatomically speaking it's locationalist without studying this stuff I would think the biceps would have an origin probably at the top of the humerus because it's going to work to flex the arm I would think it's pulling on that but it's actually pulling on the scapula so let's take a look at how that works here we have the two heads of the biceps brachii this medial one is going to extend all the way up and connect to the coracoid process whatever you're flexing your bicep like this that muscle is actually pulling up on the coracoid and the other head of the biceps brachii is where it gets really weird in my opinion so the tendon of the other head of the biceps brachii extends up and then under the tendons of the subscapularis it's kind of like there's a little Tunnel right here the head of this is going to thread up through there and then it's going to make sort of a 90 degree turn and then it's going to connect back over here on the scapula so again whenever you Flex that elbow joint using your biceps brachii that tendon is threaded up under the subscapularis tendons and then Cuts media really all the way over to the scapula right here and those are the two origins of the biceps brachii they're both on the scapula one right here on the coracoid and then the other back here on the scapula now if you look this stuff up online sometimes you'll see something called the transverse ligament and I originally had this on the drawing as this extra little ligament here that kind of crosses over right there and that the biceps brachii kind of goes under it first before going up under the subscapularis but then I did a little bit of digging and I found a research study where they had dissected I think like 14 cadavers maybe and then done a bunch of MRIs and stuff to see if there's actually a distinct transverse ligament besides just the extension of the fibers of the subscapularis and it turns out from what they found there is no separate transverse ligament but I thought this was fascinating just because when you look up diagrams sometimes it's there sometimes it's not but apparently best as I can tell transverse ligament it's not its own distinct thing it's really just the extension of the subscapularis tendon that the biceps brachii tendon is threaded up through all right quick recap we've got the infraspinatus and teres minor is going to rotate the shoulder back we have the supraspinatus which along with the deltoid muscle is going to abduct the arm or raise the humerus on the anterior or front side we have the subscapularis which along with the pectoralis major is going to work to rotate the humerus or the shoulder forward or anteriorly a common injury is a torn rotator cuff that most often happens in the supraspinatus tendons right here those rotator cuff muscles have four main functions that's stabilization of the joint concavity compression whenever you abduct the humerus it kind of pulls the humeral head in or medially and then for movement which we just talked about all right now here's a blank diagram of all of the ligaments and bones and parts of the bone in the shoulder joint take a minute pause the video see if you can go through and name every ligament and every bone and every part of the bone in this diagram showing the answers in five four three two and all right we have the humerus the scapula the parts of the scapula including the acromion and the coracoid we have the clavicle we have the sternum and then we have all of those ligaments we've got the acromioclavicular ligament number one we've got number two the sternoclavicular number three is the coracoacromial number four is the coracoclavicular number five is the joint capsule number six is the coraco humeral ligament and then number seven is the inferior Superior and middle glenohumeral ligament and then finally here's a blank diagram of the rotator cuff muscles so take a minute pause the video see if you can name all the rotator cuff muscles as well as the function of the rotator cuff answer showing in five four three two and we have the supraspinatus the infraspinatus and the teres minor we've got the subscapularis those are the four rotator cuff muscles we have the biceps brachii here which we included because it's sort of anatomically relevant to the shoulder joint we've got the transverse ligament here which isn't a distinct thing it's really just the subscapularis tendon and the functions of the rotator cuff include stabilization of the joint concavity compression for whenever you abduct the shoulder as well as movement which includes abduction for the supraspinatus and then rotation subscapularis posterior rotation and infraspinatus and teres minor anterior rotation look I'm going to be posting a bunch more Anatomy videos so if you're studying Anatomy click the Subscribe button to follow along for some more Anatomy content and then up here is another video that you might be interested in for learning Anatomy alright thanks for watching catch you in the next video