hi everybody dr mike here in this video we're going to take a look at synovial joints the first thing you need to remember is that there's three major joint types in the body there's fibrous joints which don't really have much movement there's cartilaginous joints which have a little bit of movement and there's synovial joints which are freely movable so the focus of this lecture is going to be those synovial joints if you were to take a stereotypical or general synovial joint which i've drawn up here there's a couple of things you need to be aware of that all these joints have first thing is when you've got one bone articulating or speaking to another bone like we've got here there's going to be cartilage lining the surface of those bones this cartilage is called articulating cartilage which basically means communication cartilage and the type of cartilage that's present is hyaline cartilage it's there because it reduces the friction at the site where that first bone talks to the second bone the other thing that you're going to find is that all synovial joints will have a synovial capsule also known as an articular capsule now that contains two particular things that you need to be aware of one is that there's a fibrous layer which we can see here this is dense connective tissue really important because it holds that joint nice and tight second thing is there's a synovial membrane this is on the inside of that joint and it has simple squamous epithelia now squamous remember squished epithelia it produces a fluid and this fluid is called synovial fluid so you've got synovial fluid in the joint capsule itself and what the synovial fluid does is one creates this frictionless environment similar to what these articulating cartilage surfaces are doing on the bone two it provides cushioning so that when there's some sort of impact at the bone it helps reduce that force and three it helps deliver nutrients and takes nutrients or i should say wastes away from the site that's what the synovial fluid does in the joint capsule so as you can see that's a generalized view of a synovial joint so one they're freely movable two they have articulating surfaces with articulating cartilage which is hyaline cartilage three they have a capsule which has a fibrous layer and a synovial membrane that produces synovial fluid now there's six different types of synovial joints that you need to be aware of and they can be basically categorized as being uniaxial meaning it only moves in one plane biaxial moves in two planes and multi-axial moves in more than two planes so i'll talk about this in more detail in a second but let's go through how we can remember the six different types of synovial joints so luckily i've created a mnemonic for you and this mnemonic is prince harry pooled charles's saddle bag now you can interpret that any way you like it doesn't matter it's a mnemonic it just helps us remember something prince harry pulled charles's saddlebag right remember what a mnemonic is is you can take the first letter of each of these words and that's going to tell you the first letter of each of the words we need to remember so the six synovial joints one two three four five six so what are the six synovial joints well they're going to be p is going to be planar it's a planar joint that's the first one h is going to be hinge it's a hinge joint p is going to be a pivot joint c is going to be a condylar joint s for saddle is actually going to be saddle that makes it easy to remember saddle joint and b is a ball and socket joint so the six different types of joints planar hinge pivot condylar saddle ball and socket and the great thing is it goes from being uniaxial biaxial multi-axial so let's actually highlight those the first three here are uniaxial only moves in one plane condylar and saddle biaxial moves in two planes and ball and socket multi-axial moves in many planes all right now let's draw them up have a look at the different types so first we're going to look at is going to be a planar joint now an example of a planar joint first is that if we take the hand take the bones of the hand and you have a look at all the bones of what we've got the carpals here and you take the quitretrum and the hamate now these two bones their articulating surface is going to be that of a planar joint and what does it look like because that doesn't really show it too well it looks like this you have one flat surface and another flat surface and again it only moves in one plane and this is going to be a planar joint so it's like a gliding joint is another way of explaining it so the quitretum and the hamate let's move on to the hinge joint hinge is simple it's like a door how the door opens and closes and i'm doing that with my arm funnily enough because my elbow joint is a hinge joint so let's take a look i've drawn the humerus the radius the ulna and here's the elbow joint and again unsurprisingly you've got the articulating cartilage here i haven't joined up the synovial joint aspect or capsule because it just makes it a bit more difficult but this is a hinge joint and so if i were to join draw a hinge joint up a hinge joint is going to be like the hinge of a door and only moves in one axis hinge joint perfect next one we need to look at is going to be a pivot joint now a pivot joint and the example of it here is the first and second cervical vertebrae which is c1 and c2 i'll talk about that in a sec it's where you've got a rounded bone and that rounded bone sits within a circular bone or ligament in this case for c1 c2 it's a ligament and it can only move in one axis it spins turns around so what happens in this case is c2 your second cervical vertebrae known as the axis has a protrusion called the dens and it sits underneath c1 which is known as the atlas and that dens moves up and through and you've got this ligament here and what it allows is for the head to turn so axis which is another name for c2 means turning spinning right because that's what that one does atlas doesn't and atlas is named after that god that's holding the world above its head meaning the head the skull right so that's the atlas so that's an example of a pivot joint now what we've drawn up are all the uniaxial joints right look at the the um sorry the planar joint at the triquicurum and the hamate and it just glides we've got the hinge joint at the elbow and it just swings open and closed like a door we've got the pivot joint at c1 and c2 and it just turns around these are all the uniaxial let's move on to the biaxial biaxial first of which is going to be the condylar joint now the condylar joint the example is at the metacarpal and the proximal phalanx from two to five all right two to five so the way that this condylar joint works is similar to a ball and socket similar-ish but definitely not as deep as a ballon socket and we haven't done ball and socket yet and again it moves only in two axes so if it was one axi or axis it would be like this but it's two okay so it's two different planes in which it can move and again the example is the metacarpal and the proximal phalanx that's the condylar joint then we move off to the saddle joint now the saddle joint is like sitting on a saddle right an example of a saddle joint is the trapezium and the first metacarpal and a saddle joint if i can draw it up it's actually quite difficult to draw that's a saddle joint we've got those two surfaces and they can move in two different axes saddle joint again trapezium first metacarpal now we move on to the last of the synovial joints a multi-axial joint that's going to be a ball and socket joint that of the hip where the femur articulates in to that hip joint and we know that this is a great example it's a nice deep joint and because it's a deep joint you've got that room for movement and it's a pretty strong joint as well but it moves in not just two planes but it moves in many planes and this is going to be a multi-axial joint that where the femur articulates in at the hip itself so let's just quickly label to finish off right so we've got the planar joint at the the triquetrum and the hamate we've got the hinge joint at the elbow we've got the pivot joint where we've got the pivot joint up here at c1 c2 we've got the condylar joint which is going to be the metacarpal and proximal phallics we've got the saddle joint which is going to be at the first metacarpal and the trapezium and we've got the ball and socket joint at the hip ball and socket and these are the six different types of synovial joints that you need to remember