Introduction to Joints - Video Tutorials & Practice Problems

Introduction to Joints

In this video, we're going to begin our introduction to joints. And so recall from our previous lesson videos that the human skeleton has over 200 bones and almost all of them contact other skeletal elements at joints. Now, a joint is also known as an articulation or an arthrosis. And so when we say that one bone articulates with another bone, we just mean that those bones form a joint and a joint as its name implies is going to join things together. And so a joint or an articulation or an arthrosis can be defined as a contact point between two or more bones or between a bone and tooth. And recall that teeth are technically not considered bone since they have a different composition. Now, it's helpful to note that the root arthur or arthro is a root that means joint and we can see that root in the word arthrosis as well as part of the root in the word articulation. And the word arthrology is a word that means the scientific study of joints. Now, in addition to bones and teeth, joints can also contain a variety of other structures as well, including different types of cartilage such as hyaline cartilage and fibrocartilage ligaments, which recall are dense connected tissues that connect bone to bone tendons, which recall are dense connective tissues that connect bone to muscles and muscles themselves. And so the presence and the roles of these particular structures can vary depending on the type of joint. And so different joints have different structures and functions and essentially that dictates the roles and presence for each of these structures that are listed. Now, it's important to note that joints actually serve two essential functions that we have numbered down below. Number one and number two. And so the first essential function that joints serve is that they help to facilitate skeletal mobility or skeletal movement. And the second essential function of joints is that they help to provide structural stability. Now, it is important to note that there is a balance between skeletal mobility of a joint and structural stability of a joint. And so these two are inversely related to one another, which means that the greater the range of motion, a joint has the less stable that joint will be and the less motion that a joint has, the more stable that the joint will be. And so for example, the joints that connect our bone to our teeth, keep our teeth pretty still or stationary. And so our teeth don't really move around a whole lot. And so because they have less motion, that means that they are more stable, whereas our shoulder joint that connects our humerus to our scapula, for example, has a lot of motion and because it has a lot of motion, it is less stable. And because it's less stable, it's more prone to injuries. And so let's take a look at our image down below where we can see a few examples of these joints. And so notice on the far left, we're focusing in on this human skeleton on these specific regions. The first region is the hand. And so we're showing you a zoom in here of finger joints. And so notice here is the hand which has a variety of different bones. And up above, we're zooming in on the finger joints. And so notice that the finger has a variety of bones that you can see highlighted here and the contact point between these bones which are circled here are the joints. Now, we're also focusing in on the shoulder joint which you can see over here and the shoulder joint is going to connect the humerus, this long bone of the upper arm to the scapula, which is our shoulder bone. And notice that involved in this joint is some cartilage which you can see here. And we're also showing you some muscles and some tendons and there are also ligaments involved in this joint as well. Now, over on the far right, we're also focusing in on the teeth and so of the bone to teeth or tooth connection is also considered a joint. And so notice here we're zooming in to the tooth and notice the tooth is being connected to the jaw bone, which you can see underneath here. And that is considered a joint and recall that teeth are technically not considered bones because again, they had different composition and moving forward. In our course, we're going to talk a lot more about joints, including their structures and functions. But for now this year concludes our brief introduction to joints. And so I'll see you all in our next video.

Introduction to Joints Example 1

So here we have an example problem that wants us to rank the following joints in order from the least range of motion, which will label as number one to the greatest range of motion, which will label as number four. And then it wants us to predict how this would affect their ability to provide structural stability and support. And so notice that the four joints we're showing you here in this example are the shoulder joint, which of course is found in our shoulder, connecting the humerus to the scapula. And the sutures of the skull are also a joint. And those sutures are essentially these cracks that you can see in the skull highlighted there. And then we have the intervertebral joints which are found in our spine in our back. And then last but not least we have the knee joint, which of course is found in our knee. Now, in terms of the range of motion, we can go through each of these one by one. And in our shoulder joint, of course, our shoulders have quite a lot of movement and our spine allows us to lean forward and lean backward, which also allows for some movement. And of course, our knee joint allows for movement of our knee. However, what you'll notice is that the sutures of the skull, again, these cracks, essentially that you can see here highlighted in the skull are not very mobile. And so they do not have a great range of motion. They have very low range of motion. And so for that reason, they have the least range of motion of all the joints here. And we can label the sutures of the skull as number one for having again, the least range of motion. Now again, our spine does allow for some motion, we're able to lean forward and lean back. However, the range of motion of our spine is limited and it does not allow for as great of a range of motion as the knee or the shoulder, for example. And so the intervertebral joint is going to be number two in terms of the order or the ranking of the range of motion. And then the knee has less range of motion than the shoulder. And so for that reason, we can label the knee joint as number three and the shoulder joint has the greatest range of motion of all of these joints. And so, uh we'll label it as number four. And so now that we've ranked these four joints in terms of their range of motion, let's focus in on their ability to provide structural stability and support. And so recall from our last lesson video that there is an inverse relationship between the skeletal mobility of a joint and the structural stability of a joint. And so the greater one is the less the other is. And so the greater the range of motion, a joint has the less stable that joint is. And so again, the shoulder joint here has the greatest range of motion of these four joints. And because it has the greatest range of motion, it also is the least stable and that makes it more prone to injuries such as dislocations, for example. Now the sutures of the skull, again, these cracks that you can see here in the skull are uh are going to have the least range of motion here amongst these four joints. And so because it has the least range of motion, it has the greatest structural stability amongst these four joints. And that's going to be very, very important for the skull to have great structural stability because the skull plays a critical role in protecting our brain. And so, of course, we want to prioritize structural stability and support when it comes to the skull and protecting our brain. And so this here concludes our example problem and we'll be able to get some practice applying these concepts and learn a lot more about joints as we move forward. So I'll see you all in our next video.

Why is dislocation of the shoulder joint one of the most common joint injuries?

• A. Most sports put a lot of stress on the shoulder joint.
• B. People often try to lift things that are too heavy.
• C. It has a very large range of motion, meaning it's relatively unstable.
• D. It's designed to dislocate to allow us to have a greater range of motion.

Map of the Lesson on Joints

In this video, we're going to introduce our map of the lesson on joints, which is down below right here. And because this is a map of our lesson, it is essentially a table of contents that you can continuously use to help guide you through our lessons on joints. Now, as we move forward in the lesson, we will also double click to expand and compress portions of the map in order to make this map even more relevant to you as we move forward. Now, the way that we're going to follow this map is from a top to bottom approach, but also from a left to right approach. And so notice at the very top of the map, we have the introduction to joints, which is where we currently are in the lesson and moving forward, we are going to cover the functional classes of joints. And as you can see here in this map, there are three functional classes of joints and they are the synarthroses, the amphiarthrosis and the diarthrosis. Now, one thing to keep in mind here is that moving forward in our lesson, we are going to use these symbols to represent each of these functional classes. And so uh as we'll learn, moving forward in our course, the functional classes of joints are actually categorized based on the amount of movement or the amount of mobility that the joint allows for. And so synarthroses are actually immovable joints that do not allow for any movement. And because that's the case notice that the symbol does not have any movement, arrows going around it. Now, the a arthrosis as we learn, moving forward in our course, actually allow for a little movement. And because that's the case, notice that they, the symbol that we use has one movement arrow going around to remind us that anti arthrosis have a little movement. Now, the diarthrosis as we'll learn, moving forward in our course, allow for dynamic or a free or large range of movement. And because that's the case, notice the symbol that we use has multiple movement arrows going around it to represent that dynamic movement of these diarthrosis. And so once again, moving forward in our course, we will utilize these symbols to represent each of these functional classes. Now, what you'll notice is moving forward in our course, we will then cover the structural classes of joints and notice that there are also three structural classes of joints which are the fibrous joints, the cartilaginous joints and the synovial joints. And so notice that there are multiple fibers, joints that include sutures, gums and Sindiso. And what you'll notice is that the sutures are going to be categorized as sin arthrosis because it has the red symbol around it. And so what this means is that the sutures are immovable joints that don't allow for any movement as we'll learn, moving forward in our course. And the same applies for the gum phos, the gums are a type of fibrous joint that are also categorized as sin arthrosis because again, it has that red S symbol around it. However, notice that the sends moses have the blue a around it. And so it is actually categorized as an amphiarthrosis, meaning that it allows for a little movement as we learn, moving forward in our course. Now, when it comes to the cartilaginous joints, there are two types and they are the synchondrosis and the syntheses. Now, the synchondrosis are categorized as sin arthrosis because again, it has that red s around it, meaning that it is going to be an immovable joint that it does not allow for any movement. And then these syntheses have the blue a around it, which means that they are categorized as amphiarthrosis, meaning that they allow for a little movement. And so you can see how the functional classes of joints overlaps with the structural classes of joints in that fashion. Now, when it comes to the synovial joints, it turns out that they are all categorized as diarthrosis, meaning that they allow for dynamic or a wide range of movement. And so what you'll notice is that we've got the different types of synovial joints listed here including plain joints, hinge joints, pivot joints, condylar joints, saddle joints, ball and socket joints. And notice that all of them have this symbol here that represents the diarthrosis. And so moving forward in our course, we'll be able to again utilize these symbols for sin arthrosis, anti arthrosis and diarthrosis. And we'll be able to learn a lot more about each of these different types of joints. And so this here concludes our brief lesson on the map of the lesson on joints. And I'll see you all in our next video.

Which of the following is a correct description of syndesmoses?

• A. Fibrous synarthrosis.
• B. Cartilaginous amphiarthrosis.
• C. Fibrous amphiarthrosis.
• D. Fibrous diarthrosis.