Structural Class: Cartilaginous Joints - Online Tutor, Practice Problems & Exam Prep

Introduction to Cartilaginous Joints

In this video, we're going to continue to talk about the structural classes of joints by focusing specifically on the cartilaginous joints. And so, in cartilaginous joints, as their name implies, the bones are going to be bound by cartilage. Either hyaline cartilage or fibrocartilage, but not so much elastic cartilage. And so, recall from our previous lesson videos that hyaline cartilage and fibrocartilage are tough yet flexible specialized connective tissues that are able to resist both tension and compression forces. And so, this makes cartilaginous joints structurally stable. However, recall that the structural stability of a joint comes at the cost of the mobility of the joint. And so, although cartilaginous joints are structurally stable, they are going to have limited movement. And so, like fibrous joints, cartilaginous joints are always going to be classified functionally either as synarthroses or amphiarthroses which is why we have the symbols for them here. And so again, notice the symbol for synarthroses does not have any movement arrows going around it, which can hopefully be helpful to remind you that synarthroses are still or stationary joints that essentially allow for no movement and are generally classified as immovable joints. And notice that the symbol for amphiarthroses has just one movement arrow going around it. Which can hopefully help you remember that amphiarthrosis allow for just a little or an average amount of movement, if you will. Now, really there are 2 types of cartilaginous joints. And they are the synchondroses and the symphysis. And so, moving forward in our course, we're going to talk about each of these 2 cartilaginous joints in their own separate videos. Starting with the synchondroses. So, I'll see you all there.

Synchondrosis (Plural: Synchondroses)

In this video, we're going to talk about the first type of cartilaginous joint in our lesson, which is the synchondrosis. And the plural form is synchondroses. Synchondroses are cartilaginous joints where bones are bound specifically by hyaline cartilage. It's helpful to recall that the root chondro, found in the word synchondroses, means cartilage. Recall from our previous lesson videos on cartilages that hyaline cartilage is a tough yet flexible specialized connective tissue that can resist tension forces. The hyaline cartilage in these synchondroses makes them structurally stable, providing structural stability. However, recall that the structural stability of a joint comes at the cost of the mobility of the joint. Although these synchondroses provide structural stability, they essentially allow no movement. Therefore, they are always classified functionally as synarthroses. Notice that the symbol for synarthroses does not have any movement arrows going around it, which can be a helpful reminder that these synarthroses are still or stationary joints that essentially allow for no movement and are generally considered immovable joints. Now, similar to sutures, eventually, some synchondroses bones may actually fuse together to become a synostosis or a bony joint. Recall that the root ost means bone, which can remind you that a synostosis is when two or more bones fuse together into a single bone. The hyaline cartilage in these synchondroses can eventually ossify, meaning it can be replaced by new bone tissue. Not all synchondroses will ossify to become a synostosis; only some of them will. Usually, the ones involved with growth and development will turn into these synostoses, such as the epiphyseal plates, which we'll get to see down low in our image. Notice here, in the middle of the image, we have this human skeleton, and we're focusing in on very specific regions. On the left-hand side, we're focusing in on the femur, and you can see here is the femur. Notice that we're zooming into the top portion here of the femur, and what you'll notice is that these blue lines, indicated with arrows, are the epiphyseal plates, also sometimes referred to as growth plates. These are synchondroses where hyaline cartilage is connecting bones; it is connecting the epiphysis of the bone to the diaphysis of the bone. These epiphyseal plates can be found in long bones, such as the femur, the humerus, and the tibia. These epiphyseal plates, in children and adolescents, will be present. But, when they reach adulthood, these epiphyseal plates will ossify, and the bones will fuse together to create synostoses. Now, notice over here on the right side, we're focusing in on another example of synchondroses, which is between the first rib and the sternum, specifically the manubrium of the sternum or the superficial portion of the sternum. Here we have the first rib being connected to the manubrium of the sternum by the hyaline cartilage you can see here. This is a synchondrosis. It is only the junction that connects the first rib to the sternum that is considered a synchondrosis. Many of the other ribs that lie beneath are going to have junctions that are considered synovial joints. We'll get to talk more about those later in our course. This here concludes our brief lesson on synchondroses, and we'll be able to get some practice applying these concepts and learn about the other type of cartilaginous joint as we move forward in our course. I'll see you all in our next video.

Structural Class: Cartilaginous Joints Example 1

So here we have an example problem that asks how are synchondroses similar to sutures? And we've got these four potential answer options down below. Now, option A says that they are both made of rigid hyaline cartilage. But of course, we know that this is not true for sutures because recall that sutures are a type of fibrous joint where the bones of the skull are connected by dense irregular connective tissue, not connected by hyaline cartilage. And so for that reason, we can eliminate answer option A.

Now, option B says that the epiphyseal plates and sutures can both ossify over time to form synostoses, and recall that the epiphyseal plates are examples of synchondroses. And so recall from our previous lesson videos that this is actually true. The hyaline cartilage and epiphyseal plates can ossify over time to form synostoses, and the sutures of the skull can also ossify over time to form synostoses. And so, because option B is true, we can go ahead and highlight it as the correct answer option. And recall that ossification just means the replacement or the formation of new bone tissue. And, synostoses recall are just when two bones fuse together into a single bone.

Now, let's check options C and D just to be sure. Option C says that the costosternal synchondrosis and sutures both allow a small amount of movement. But recall that joints that allow for a little or an average amount of movement with a slight amount of movement are categorized as amphiarthroses. But recall that synchondroses and sutures are both classified as synarthroses, meaning that they are stiff or stationary and generally considered immovable joints. And so option C is not going to be the best option for this example.

Now, option D says that they are both fibrous joints, but of course, we know that this is not true. We know that sutures are considered fibrous joints. However, the synchondroses with that root chondro, that means cartilage, it is going to be a cartilaginous joint, not a fibrous joint. And so that's why we can eliminate option D.

And so this here concludes this example problem, and I'll see you all in our next session.

Which of the following statements is true?

• A. Synchondroses can be either synarthroses or amphiarthroses.
• B. Synchondroses are more functionally similar to syndesmoses than gomphoses.
• C. Synchondroses can be found in both the axial and appendicular skeleton.
• D. All statements are true.

Symphysis (Plural: Symphyses)

In this video, we're going to talk about the second type of cartilaginous joint in our lesson, which is the symphysis. And the plural form is symphyses. What's important to notice about the symphysis is that they have a unique spelling that we can actually use to our advantage to help us remember important features about these symphyses. Unlike many of the other joints that we've talked about in our previous lesson videos, which start with the letters "syn" as in Nancy, the symphyses start with the letters "sym" as in Mary, and that "m" is quite unique to these symphyses, for that reason. We can utilize this letter "m" in symphyses to help us remember key features about these symphyses. What you'll also notice is unique about the symphyses is not just the letter "m", but also the letters "ph", which phonetically make an "f" sound. Together, the "m" and the "ph" can help us remember critical features about these symphyses. This is why we have those letters underlined here underneath symphyses.

Symphyses are cartilaginous joints in the body's midline, and they're found always in the center or the midline of our body. That is where the "m" in symphysis can help us, with remembering that these symphyses are found in the body's midline. They are specifically bound by fibrocartilage. The "ph" in symphysis, which phonetically makes an "f" sound, can remind us of the "f" in fibrocartilage. Hopefully, by utilizing these memory tools, you can easily remember the most important features of these symphyses.

Recall from our previous lesson videos that fibrocartilage is designed for strength and flexibility. The fibrocartilage found in these symphyses actually does allow for a little movement. Because it does allow for a little movement, they are always going to be functionally classified as amphiarthroses. Again, notice that the symbol for amphiarthroses has just one single movement arrow going around it, which can hopefully help you remember that these amphiarthroses allow for just a little or an average amount of movement. Also recall from our previous lesson videos on cartilages that fibrocartilage is very compressible, resilient, and flexible, and because that's the case, this allows symphyses to act as shock absorbers. That will be very important to their functions.

Let's take a look at our image down below where we can see a few examples of these symphyses. Notice here we have our human skeleton, and we're focusing in on specific regions. On the left-hand side, we're focusing in on the spine of this human skeleton. What you'll notice is that the intervertebral joints found in the spine are actually going to be these symphyses. Again, the spine is found in the midline of our body, and of course, the symphysis is going to contain fibrocartilage connecting the bones, which in blue, represents the fibrocartilage. It is extremely compressible, resilient, and flexible, allowing it to act as a shock absorber. This is really important for our spine to be able to do since it's constantly having to fight against gravity, and it's constantly being compressed, and it needs to be able to absorb shock. Recall that amphiarthroses, the root "amphi" is a root that means both or both sides. Amphiarthroses allow for movement on both sides of the joint. This allows this symphysis to have movement on both sides, and so this allows us to be able to lean backward and also lean forward. Collectively, these symphyses are amphiarthroses and so they allow for a little movement, but collectively, all of the intervertebral joints that allow for a little movement can build up and stack up, allowing our spine to have a pretty decent amount of movement, but the individual joint is an amphiarthrosis.

Now, on the right side of the image, we're focusing in here on the pelvis, and what you'll notice is that here, right in the midline again, we have what's known as the pubic symphysis. The pubic symphysis is found here in the pelvis, connecting the bones on both sides, and it will allow for movement on both sides of the joint. Again, it's made up of fibrocartilage, so it is extremely resilient and compressible and can act as a shock absorber for movements in our body. This concludes our brief lesson on symphysis, and we'll be able to get some practice applying these concepts and learning more about other joints as we move forward in our course. So, I'll see you all in our next video.

Structural Class: Cartilaginous Joints Example 2

So here we have an example problem that asks which type of joint would be best suited to withstanding a great deal of mechanical stress while also being compressible in order to absorb shock. And we've got these 4 potential answer options down below that include synchondroses, syndesmoses, symphyses, and gomphoses. And so, of course, recall from our previous lesson video that symphyses are going to contain fibrocartilage, and you could think that the "ph" noise phonetically can remind you of the "f" noise in fibrocartilage. And so, recall that the fibrocartilage is going to allow for a great deal of mechanical stress, withstanding a great deal of mechanical stress, while also being compressible in order to absorb shock. And so the correct answer to this problem is answer option c, symphyses. Now synchondroses are going to be cartilaginous joints made of hyaline cartilage, but the hyaline cartilage does not allow for shock absorption like fibrocartilage does. And so for that reason, we can eliminate answer option a. Now, syndesmoses and gomphoses are both types of fibrous joints that utilize fibrous connective tissue, mainly dense irregular connective tissue, which allows for a lot of strength. However, it does not have the shock absorbing properties that fibrocartilage has. And so for that reason, we could have eliminated answer options b and d. And so again, option c, symphyses, is the correct answer to this example. I'll see you all in our next video.

Which joint type is primarily responsible for allowing growth in long bones during childhood?

• A. Syndesmosis
• B. Synchondrosis
• C. Symphysis.
• D. Gomphosis.

Which of the following describes a cartilaginous joint?

• A. The amphiarthrosis between the radius and ulna, allowing for forearm rotation.
• B. The freely movable shoulder joint, which contains articular and hyaline cartilage.
• C. The synarthrosis between bones of the skull.
• D. The amphiarthrosis between adjacent vertebrae in the spine.