Synovial Joints

now let's have a look at the synovial joints so firstly what is a synovial joint I spoke to you about those various classes of joints and I told you that you can have fibrous joints cartilaginous joints and synovial joints how do the first two fibrous joint account letters joints quite in mobile joints sometimes they're fully in mobile or sometimes they're partly mobile but when we start talking about freely movable joints what we're referring to are the synovial joints there's a couple of points about synovial joints which make them very specific and very particular so what I've drawn here to the best of my ability is a synovial joint so let's point out a couple of important regions anatomically and discuss what they do so first thing I wanna highlight is we have two long bones so we have one long bone here articulating with another long bone here so this could be either the humerus with potentially it could be the glenohumeral point but it's not necessarily because it's two long bones so it must be the knee for example so this could be where the tibia comes into the femur now couple of things these little swirls that I've drawn this indicates the spongy bone and then what you can't see towards the outside of bones what we call the compact bone now I've filmed a video looking at the differences between compact bone and spongy bones so please watch that and you can see that in this little cavity in the middle of these long bones which we call them the gallery cavity we've got some yellow bone marrow which is fat so it's an ability the medullary cavity is one place where we can store energy in that form of fat we've also got this little line that I've drawn here on both of these long bones that this is what we call the epiphysis line also the Fasil plate and this is when children growing up I've spoken to previously about in the epiphysis so you've got your whole long bone the diathesis is the shaft of the bone the epiphysis is on both ends proximal epiphysis distal epiphysis and in this epiphysis there is a plate that when you're younger this plate was cartilaginous and would allow for bone growth to occur so it would secrete all this extracellular matrix and then calcium and phosphate would come along and harden that bone so as an adult this bone snaps to ossify and Harden and it just becomes what we call the picker silver line in addition to that we can see this blue line that I've drawn that's articular cartilage which I've spoken to previously being of the subtype of hyaline cartilage and it's this glassy smooth cartilage at articulating bone surfaces so bones can glide across and create a frictionless environment to aid in that frictionless environment we have this membrane here which is typical of synovial joints and it's called the synovial membrane and it releases a fluid in the joint capsule space called synovial fluid and again this fluid reduces friction we've also got the fibrous portion of this capsule so the capsule here is made up of the synovial membrane and the fibrous membrane here which sort of encapsulates the whole joint apart you can also see we draw a little bit of the periosteum which is the outside aspect of the bone that periosteum goes along the outside aspect of all bones however when it comes to an area of articular cartilage there is no longer any periosteum it then turns into articular cartilage so now what I want to talk about are the different subtypes of synovial joints how freely moveable they are and where you can find them in the body with the help of our friend Frank so firstly when we look at the synovial joints we can so what I've just done those in my own head I've got a mnemonic for the joints for the synovial joint a mnemonic is where you take the first letter of every word and you attribute it another word that's easier to remember and simply say planar hinge pivot and so forth okay now usually I'll tell you what the mnemonic is such as when we do the 12 cranial nerves we go oh oh to touch and feel very good velvet ah heaven for the epidermal layer then taking men Theresa there's a system we say come let's get sunburnt for the five players of the epidermis now this one unfortunately if I were to tell you I would get fired because it's too disgusting for me to say so in saying that this is a good opportunity for you to create your own type of mnemonic now let me tell you what there's three four five six different types of synovial joints our first one is called a planar joint the next one is called a hinge joint then we have a pivot joint then we have a condylar joint a saddle joint and a ball-and-socket joint now I have intentionally drawn up three to one because this is the order in which they go from least movable to most movable or I should say moving in the least amount of planes go into the most amount of planes let me tell you what I think playing a hinge and pivot joints of synovial joints a uniaxial uni-axial means it only moves in one plane either back and forth or up and down left and right for example condylar and saddle joints are biaxial we can move in two planes which means they can go forward and back and up and down for example ball and socket joints are multi axial and therefore they cannot just move up and down and left and right and forward and back and die and so forth they basically can move in many directions so you probably know what type of joint is a ball-and-socket joint okay now a planar joint a planar joint is basically like two flat pieces of material coming together and they will either just move up and down or forward and back so that's a planar some of your joint we can we find a playlist on well let's bring Frank into the picture a plate of synovial joint is the top that you can find in the hand now the hand has many different types of bones so please remember that you will have your capitals here your metacarpals here and then your phalanges here so carpals metacarpals then you can have your proximal phalanx middle phalanx distal Alex place that you can find that planar joint is that the carpals in what we call the inter carpal joint so between carpals or where you can find planar joints so we can write into carpal joint inta couple joint what about a huge joint this one's pretty easy because you know what the hinges their hinges something you can see on a door and basically it moves the way my own convert which means that a hinge joint is the type of joint you define between the owner and the humerus so the owner humerus joint here is a huge job okay what about pivot joint what's a pivot joint well a pivot joint is basically when you have something like this which can give it around like that so spinning around so where could we find a joint I can spin well if we have a look at Frank again let's turn around if we have a look at is vertically now again I've recorded a video on the vertebra so you can watch the video on the vertebral column very simply you've got different types you've got some like or vertebrae thoracic vertebrae lumbar vertebrae sacral and coccygeal and if you look at the seven cervical vertebra the top to c1 or survivor 1 c2 survival - quite different the very top c1 is also known as the atlas why is it called the atlas do you know that Roman god I think it's a Roman god or great god that's holding the world above it holding that world up well that's synonymous or at least trying to be synonymous with this Atlas the c1 holding the skull about the one below is called the axis okay and the reason why it's called the axis is because it spins on an axis so c1 atlas holding the world above it c2 axis because the spins around which means that c2 cervical vertebrae - is a good example of a pivot joint so there's a survival vertebrae sorry about my writing see - okay what about a Khandala joint so we're now moving into the biaxial around a candle a joint so looks like that so silicon rock back and forward and left and right that's a Khandala joint so if we can have a look to see where we can find the kind of a joint take back again how little joint is the typical joint that you'll find between the metatarsal and the proximal facts sided between the metatarsal and the proximal phalanx that joint there is what we call the condom our joint metacarpal and proximal that works but saddle joint think about somebody sitting on the saddle of a horse so how does that look well the saddle of the horse sort of looks quite strange and then the joint coming in looks quite strange as well so it's not the best drawer let me try that again obviously I'm not the best drawer I do apologize but a saddle joint sullen looks a little bit like that it's pretty terrible joy but think of sitting on the saddle little horse pop and that being said terrible let me give you an example as to where you can find a saddle joint one simple place is if you can you take the hand all these joints can be found in the hand take that thumb from the metacarpal to one of the couples here which we call the trapezius so that your peers in here we go from the metacarpal to one of the carpals here in the thumb that is going to be what we call they Sal joint all right last one ball in Suffolk this one it's easy think of a bubble think of the ball being inside of a socket that's what you can find here at the glenohumeral joint I'll bring Franklin picture the glenohumeral joint meaning the ball the head here of the humerus and so the scapula here got a humeral joint or even the head of the femur in at the hip both of these are examples of ball and socket joints now even though they're multi axial some of these have less movement this is some of Mormons so for example the shoulder has greater movement inside of that joint but it's weaker while the hip has less movement inside that joint and it's stronger okay so let's write down two examples of ball and socket we can write glenohumeral the humeral joint which is the humerus and the joint of the clavicle and we can also say the femur and hip joint and these are examples of synovial joints so hopefully with the help of Frank that was helpful for you

Channel: Dr Matt & Dr Mike

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Length: 15min 6sec (906 seconds)

Published: Mon Mar 27 2017