 Hey everybody, Dr. O here. So we just got on talking about the functional classification of joints, but classifying them on how much they move, synarthrosis are immovable, amtiarthrosis are slightly movable, and diarthrosis are freely movable. Now we're going to look at these structural classifications of joints, and we're going to see three, but there is really four. So a structural classification, we have fibrous joints, which are joints that are held together by fibrous connective tissue. We have cartilaginous joints, which are joints held together by cartilage. And then we are going to have some bony joints. I'll show you an example of a synarthrosis, which is a joint that used to be a joint, I guess, that's connected by bone. And then we'll have our synovial joints, which are our diarthrosis or our freely movable joints. They're going to be held together by joint cavities. All right, let's go ahead and dive in. So the three types of fibrous joints we have, as you can see here, are the suture, the gonfosis, and the syndesmosis. So I have a picture of each one to show you here. Here we see the suture. So the suture is going to be an example of a fibrous synarthrosis, meaning it's held together by dense fibrous connective tissue, and it's an immovable joint. So only found in the skull, these are going to be the suture, the four sutures you learned about that hold your skull bones together. Then on the outside of the right here, we have a gonfosis. So a gonfosis, I actually call it a tongue-in-groove joint. The gonfosis is another example of a fibrous synarthrosis. So it's held together by dense fibrous connective tissue, and it's an immovable joint. Your teeth shouldn't move. If they're moving, that's a problem, unless you're losing your baby teeth, I get. Yes, so this is the kind of joint that binds your teeth into the sockets. Remember, the alveolar process of the maxilla and mandible are going to be the sockets that your teeth are actually connected to. So those are two examples, the suture and the gonfosis. Here on the next slide, we have the syndesmosis. So this is an example of a fibrous amphiarthrosis, meaning it's held together by fibrous connective tissue, but it is slightly movable. So the picture here is the radius and ulna, the radio ulnar joints here being held together by this introsius membrane. So it does allow for a lot more movement. Your forearm should move a lot more than your teeth or your sutures in your skull. Another example would be the similar joint holding the tibia and fibula together. So that's an example of a syndesmosis, which is a fibrous amphiarthrosis. All right, next we have the cartilaginous joint. So as you can see here, we have a synchondrosis, chondromeaning cartilage. So we have a synchondrosis and then we have the symphysis here. I have a picture of each one of those and I also want to talk about the bony synostosis. So here we see the synchondrosis, this is a cartilaginous synarthrosis. This joint should not move. So the example here is an epiphyseal plate or the growth plate. So the cartilage plate between the shaft of a long bone and the ends that's there while your bones are still maturing. Once you reach skeletal maturity, this should actually be replaced by a bony synostosis. So a bony joint, the bones will actually fuse together. So I don't know if you really want to classify that as a joint or not, but that's what it's called a bony synostosis. So I don't have a picture of that here. But as that epiphyseal plate is replaced with an epiphyseal line, once bone lengthening has ended, the synchondrosis would now be gone and the synostosis would take its place. So that's a synostosis, a cartilaginous synarthrosis. It should be an immovable joint. Then we have the symphysis here. So the symphysis is a cartilaginous amphiarthrosis, meaning that it is slightly movable. So the example I'm showing you here is the intervertebral discs. There's movement and mobility between your spinal bones because of that cartilage pad, the intervertebral disc. The other example in your body would be the symphysis pubis, the fiber cartilage pad between your two pubic bones. All right, so that's the synchondrosis, the bony synostosis, which you don't see here, and the symphysis. And then we have our last group are going to be structurally classified as synovial joints. These are all diarthrosis, freely movable joints, because they're not directly connected. They come into contact with each other inside the fluid filled joint cavity. So synovial joints are all freely movable. And I'll cover each of the individual movements here. You see like gliding, hinge pivot. I'll cover that in a separate video. But the other key thing to note here, though, is that we do have all these different types of movements. But for this video, I just want to talk about the fact that we can classify them by how many planes they're freely movable in. Like to say the elbow is freely movable is true. But the elbow is a hinge joint, meaning that it's uniaxial or monaxial. It's only freely movable in one plane. Whereas my wrist, for example, is biaxial. It's freely movable in two planes. Mine isn't very much because of my wrist injury. But and then my shoulder is freely movable in all planes. So it's going to be multi-axial there. So those are important terms to know. But we'll dive more in the detail with those later. All right, so that's going to be the structural classification of your joints. We have the fibrous joints, which are generally held together the tightest. So they're the most stable and least mobile joints. We have the cartilage joints. That one example of a bony joint, if you want to throw it into this category. And then we have your synovial joints, which are freely movable joints. Okay, I hope this helps. Have a wonderful day. Be blessed.