In this video, we're going to do an overview of cartilage, which is the first type of specialized connective tissue in our lesson. And so, recall from our last lesson video that there are 3 different types of cartilages. Those are hyaline cartilage, fibrocartilage, and elastic cartilage. Moving forward in our course, we'll talk about each of these 3 different types of cartilages in their own separate videos. But in this video, we're going to do an overview of all of these cartilages.
In terms of their characteristics and their properties, cartilage is actually somewhat in between that of bones and dense connective tissues. We know that bones are rock-hard structures that are very well designed for withstanding compression forces from load-bearing, heavy weights of the body. Whereas dense connective tissues, such as those found in tendons and ligaments, for example, are more so designed for withstanding tension forces from being pulled rather than withstanding compression forces from load-bearing, heavy weights of the body. Cartilage is somewhat in between these because it is a very tough connective tissue, yet it is more flexible than bones and less flexible than dense connective tissues. It is able to resist both tension forces from being pulled and compression forces from load-bearing heavy weights of the body.
As we'll learn moving forward in our course, bones are very well vascularized with lots of blood vessels. Recall from our previous lesson videos that dense connective tissues are very poorly vascularized with few blood vessels. Cartilage is somewhat in between the two because it is avascular, meaning that it has no blood vessels. This is going to cause very slow healing of cartilages upon being damaged or injured.
Cartilage is a very tough yet flexible connective tissue. It has a very firm but flexible and rubbery extracellular matrix. In terms of its cell types, there are 2 main cell types in cartilages. It's helpful to note that the root chondro is a root that means cartilage. You can find this root chondro in the two main cell types, chondroblasts and chondrocytes.
Chondroblasts are blast cells, as it ends with the root 'blast'. Recall from our previous lesson videos that blast cells are immature cells that are more active. They more actively divide and build and secrete components of the extracellular matrix, including the ground substance and protein fibers. The second main cell type are the chondrocytes, which are site cells, as it ends with the root 'sites'. Recall that site cells are mature cells that are less active. They less actively divide, and they are more so about maintaining the extracellular matrix through minor repairs and routine maintenance.
These chondrocytes are mature and are actually derived from the chondroblasts, which are immature. Chondroblasts that are actively secreting and building components of the extracellular matrix, upon actively doing that and maturing into chondrocytes, can actually become trapped in spaces within the extracellular matrix known as lacunae. These lacunae are chambers that house chondrocytes.
The perichondrium is going to be a tissue that supports most cartilages. It's helpful to know that the root peri is actually a root that means around. Perichondrium is going to be around the cartilage. It is dense irregular connective tissue, which we talked about in our previous lesson videos and we know is poorly vascularized with few blood vessels, but it still does have some blood vessels which allows it to provide blood flow to the cartilages and nutrients to the avascular cartilages.
Now, this perichondrium is found around most cartilages, including most hyaline cartilages and elastic cartilages. As we'll learn moving forward in our course, it's actually not supporting or found around fibrocartilage. We'll talk more about this as we move forward in our course. As you can see in our image, cartilages can be found all throughout the body in various structures, including our nose, where it can provide the shape of our nose.
It can also be found in our trachea. It connects the bones of our ribs to the sternum, which is our chest bone. It can also be found in between the vertebrae in our spine where it can absorb shock and provide cushioning. It's also found in between the joints in our legs and the joints in our arms, where again, it can provide cushioning and shock absorption. It can also make up structures in our ears as well.
And what you'll notice is that we have a little sketch of some cartilage. What you'll notice is that it is going to have the 2 main cell types, chondroblasts and chondrocytes. Again, these chondrocytes are going to be found in spaces, which you can see here, called lacunae. And again, the singular is actually lacuna. In a single lacunae, the space that you can kind of see going around these chondrocytes, you can either find pairs of chondrocytes as you see here, or you could find single chondrocytes.
Most cartilages, including most hyaline cartilages and elastic cartilages, are going to have a perichondrium. Again, this dense, irregular connective tissue surrounds most of the cartilages and is going to provide blood flow and nutrients. So, this here concludes our overview of cartilage. As we move forward in our course, we'll be able to talk more details about each of the 3 different types of cartilages. I'll see you all in our next video.
