Specialized Connective Tissue: Cartilage

So now that we've covered connective tissue proper, including loose and dense connective tissues. In our previous lesson videos in this video, we're going to begin our lesson on the second major class of connective tissues, which are the specialized connective tissues with a focus on cartilage for the next few videos. And so recall from our previous lesson videos that specialized connective tissues as their name implies with the term specialized are going to be optimized for very specific roles that are pretty unique to the tissue. And so this is different than connective tissue proper, which tends to have more generalized functions and roles. And also recall that specialized connective tissues tend to have a ground substance in the extracellular matrix that is either a solid or a liquid rather than being a gelatinous semifluid like the ground substance of connective tissue proper. And also recall from our previous lesson videos that there are three different types of specialized connective tissue and those are cartilage, bone and blood and lymph. And so moving forward in our course, in separate videos, we're going to talk more details about each of these three different types of specialized connective tissue and So notice down below, we have our map of the lesson on connective tissue. And so we know that connective tissues can be grouped into two major classes. The first major class is connective tissue proper or general or fibrous connective tissues, which includes loose connective tissues such as Ariola reticular and adipose tissues and dense connective tissues such as dense, regular, dense, irregular and elastic connective tissues. And so we've already covered connective tissue proper in our previous lesson videos. And so here in this video, we're focusing our attention on the second major class of connective tissues, which are the specialized connective tissues, which once again includes cartilage, bones and blood and lymph. Now, what you'll notice is that there are three different types of cartilage, including hyaline, cartilage, fibrocartilage, and elastic cartilage. And so moving forward in our course, we're going to talk about all of these different types of specialized connective tissues in their own separate videos in more detail, starting with cartilage. And so this year concludes our lesson, our introduction to our lesson on specialized connective tissue. And I'll see you all in our next video to learn more about cartilage.

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 three different types of cartilages. And those are hyaline, cartilage, fibrocartilage, and elastic cartilage. And so again, moving forward in our course, we'll talk about each of those three different types of cartilages in their own separate videos. But again, in this video, we're going to do an overview of all of these cartilages. And so in terms of their characteristics and their properties, cartilage is actually somewhat in between that of bones and dense connected tissues. And so 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. And so again, 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. And it is actually able to resist both tension forces from being pulled and compression forces from load bearing heavy weights of the body. And also, as we'll learn, moving forward in our course, bones are very well vascularized with lots of blood vessels. And recall from our previous lesson, videos that dense connective tissues are very poorly vascularized with few blood vessels. And so again, cartilage is somewhat in between the two because it is a vascular meaning that it has no blood vessels. And this is actually going to cause very slow healing of cartilages upon being damaged or injured. Now again, cartilage is a very tough yet flexible connected tissue. And so it is going to have a very firm but flexible and rubbery extracellular matrix. Now, in terms of its cell types, there are two main cell types in cartilages and it's helpful to note that the root kro is a root that means cartilage. And so you can find this root kro in the two main cell types, chondroblast and chondrocytes. And so of course, chondroblast are going to be blast cells since it ends with the root blast. And recall from our previous lesson videos that blast cells are immature cells that are more active, they more actively divide and they actively build and secrete components of the extracellular matrix, including the ground substance and protein fibers. And then the second main cell type are the chondrocytes which of course, are going to be site cells since it ends with the root sites and 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. And so again, these chondrocytes are mature and they are actually derived from the chondroblast which are immature. And so these chondroblast that are actively secreting and building components of the extracellular matrix upon actively doing that and maturing into chondrocytes, they can actually become trapped in spaces within the extracellular matrix known as Laconi. And so these Laconi are going to be chambers that house chondrocytes. And so again, these chondrocytes are going to be found in chambers within the extracellular matrix called Laconi. Now again, because cartilages are avascular, meaning they have no blood vessels, that means that they are going to need to be supported by other tissues. And so the perichondrium is going to be a tissue that supports most cartilages. And so it's helpful to know that the root perry is actually a root that means around. And so the root chond which you can see most of that root chondr and perichondrium again is a root that means cartilage. And so perichondrium is going to be around the cartilage. And so the perichondrium is actually 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 again the avascular cartilages. Now, again, this Perri is found around most cartilages, including most hyaline cartilages and elastic cartilages. But as we'll learn, moving forward in our course, it's actually not supporting or found around fibrocartilage. So, fibrocartilage is an exception. And again, we'll talk more about this as we move forward in our course. Now, 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 can also be found in between the joints in our legs and the joints in our arm where again, it can provide cushioning and shock, absorb and it can also make up structures in our ear as well. And what you'll notice is that here, we have a little sketch of some cartilage. And what you'll notice is that it is going to have the two main cell types, chondroblast and chondrocytes. And again, these chondrocytes are going to be found in these spaces which you can see here uh called Laconi. And again, the singular is actually lacuna. And so uh in a single lacuna, this space that you can kind of see going around these Condra sites, you can either find pairs of conroys as you see here or you could find single conroys. And then again, most cartilages including most hyaline cartilages and elastic cartilages are going to have a perichondrium. Again, this dense irregular connective tissue that surrounds most of the cartilages and is going to provide blood flow and nutrients. And so this year concludes our overview of cartilage. And again, as we move forward in our course course, we'll be able to talk more details about each of the three different types of cartilages. So I'll see you all in our next video.

So here we have a pretty straightforward example problem that wants us to select one of these four potential answer options down below that best fills in the blank to complete the sentence. And so it says that the primary cells of cartilage reside in blank. Option A says Laconi. Option B says gap junctions, option C says osteon and option D says that options A through C are all correct. And so recall from our last lesson video that cartilage has two primary types of cells, chondroblast and chondrocytes and the chondrocytes are the ones that are going to reside in chambers within the extracellular matrix called Laconi. And so option A Laconi is going to be the correct answer to this example problem. Now, option B which says gap junctions, those are going to be junctions that connect the cytoplasm of two neighboring cells. But gap junctions are are not really going to be a defining feature of connective tissues where the cells are usually spaced apart and not in direct contact with one another. So we can eliminate. Option B. Option C says osteon which are actually structural units of bones that we'll get to talk more about later in our course. But again, these osteens are not part of cartilage. So for that reason, we can eliminate option C and then of course, we can eliminate option D as well. And so a Laconi is the correct answer here and I'll see you all in our next video.

In this video, we're going to talk about the first type of cartilage in our lesson, which is hyaline cartilage. And so hyaline cartilage is actually the most abundant cartilage throughout the entire human body. And it's also the weakest form of cartilage amongst the three different types of cartilage. Now, hyaline cartilage is actually named for its appearance in the human body. And so hyaline cartilage appears as this bluish white color with a very smooth glassy type of appearance that can actually have some shine to it. And so, in fact, the root high all in hyaline cartilage is actually a root that means glass. And so hopefully this can remind you of hyen cartilage's very smooth and glassy type of appearance. Now, in terms of its composition, hyaline cartilage has these very small or fine or thin bundles of collagen fibers in its extracellular matrix. And so of course, we know that these collagen fibers are going to be long unb branched and straight fibers that gives the tissues lots of strength and a little bit of flexibility. And so hyaline cartilage like all cartilages is going to be a very tough connective tissue. However, because these collagen fibers are going to be arranged in very small or fine or thin bundles. Really, this is what makes hyaline cartilage, the weakest form of cartilage amongst the three different types of cartilages. Now, in terms of its function again, because hyaline cartilage has this very smooth glassy type of appearance that smooth nature actually helps to reduce friction between bones and also like all cartilages, which are very tough connective tissues with some flexibility as well. Hyaline cartilage is going to be able to serve as a very strong and flexible structural support. And very notably of hyaline cartilage is that it actually serves as the precursor to bone in the fetus. And so the human fetus and human embryo actually have skeletons that are made almost entirely of hyaline cartilage initially. And then as the human develops, that hyaline cartilage is slowly replaced with bone. And so that's pretty interesting. Now, in terms of the body locations where we can expect to find hyaline cartilage, hyaline cartilage is going to be able to serve as a strong and flexible structural support and body locations such as the nose, for example, the larynx or the voice box and the trachea or the windpipe. It's also going to be found at the ends of long bones where it will help to reduce friction between the bones. And so it can be found in areas such as our knee and our elbow and our shoulder. And uh also hyaline cartilage is going to be associated with developing bones as well. Again, because hyaline cartilage is the precursor to bone in the fetus. Again, it makes up most of the skeleton of the human embryo and is slowly replaced with bone as the human develops. And so notice over here, we have some images where you can see that hyaline cartilage is found in the nose helping to give our nose its structure and shape. It's found in the larynx and the windpipe where it's going to help to prevent the collapse of the windpipe and still allow for some flexibility for the expansion and contraction as we're breathing. It's also found connecting the bones of our ribs to the sternum or our chest bone where it can give our ribs some flexibility as it expands and contracts during breathing. And again, it can be found in uh joints at the ends of long bones where it's going to reduce friction between bones. And so notice down below, we have this micrograph of hyaline cartilage. And again, notice we are highlighting a condite within the lacuna. And so recall that the lacune are these um basically these chambers in the extracellular matrix that house the conroys, which are the mature cells of cartilage. Now, the matrix is going to be a a firm yet flexible and rubbery extracellular matrix and most types of hyaline cartilage are going to be surrounded by the perichondrium which again is a layer of dense, irregular connective tissue that is vascular and can help to support the hyaline cartilage by providing nutrients through its blood vessels. And again, like all cartilages, hyaline cartilage is avascular and not all hyaline cartilage is going to have the perichondrium. For example, the cartilage at the ends of long bones, uh sometimes referred to as articular cartilage is not going to have perichondrium mainly because it needs the cartilage needs to be available to reduce the friction between bones. And so this year concludes our lesson on hyaline cartilage and we'll be able to apply these concepts and learn about other types of cartilages as we move forward in our course. So I'll see you all in our next video.

So here we have an example problem that asks how does the appearance of hyaline cartilage help you remember its function? And we've got these four potential answer options down below. And so recall from our previous lesson videos that hyaline cartilage is actually named for its appearance. And so recall that the root high and hyaline cartilage is actually a root that means glass. And so hopefully, this can remind you that hyaline cartilage has a very smooth glassy type of appearance to it. And so it actually does not have a webbed appearance. And so for that reason, we can eliminate answer option B which says webbed appearance insulates the body that's not going to be true. And we can also eliminate answer option D which also says webbed appearance resists compression. Now hyaline cartilage does resist compression, but it's not going to have a webbed appearance. And again, that's why we can eliminate option D. So now we're between either option A or option C and notice option A says smooth appearance transports nutrients, but we never said that hyaline cartilage is important for transporting nutrients. And in fact, it's not important for transporting nutrients. And so for that reason, we can eliminate answer option A and so, of course, this means that option C must be the correct answer which says smooth appearance reduces friction. And so recall that again, hyaline cartilage does have a smooth glassy appearance to it and it can be found at the ends of bones where it can reduce friction between the bones. And so for this reason, we can indicate that answer. Option C is the correct answer to this example. And that concludes this example. So I'll see you all in our next video.

In this video, we're going to talk about the second type of cartilage in our lesson, which is fibrocartilage. And so, in terms of its characteristics, fibrocartilage is actually a little bit of a blend between hyaline cartilage and dense regular connective tissue, which recalls a type of connective tissue proper. And also recall that connective tissue proper is sometimes referred to as fibrous connective tissue. And so the root fibro and fibrocartilage can remind you that fibrocartilage is a blend between fibrous connective tissue or connective tissue proper, mainly dense regular connective tissue and a blend between cartilage or hyaline cartilage. Now, like all cartilages, fibrocartilage is avascular, meaning that it does not have any blood vessels. But unlike most cartilages in the body, fibrocartilage does not have a perichondrium or a layer of dense irregular connective tissue that surrounds the cartilage and usually has a blood supply that is able to support the avas vascular cartilage. But again, because fibrocartilage does not have a perichondrium, it does not have that supporting dense irregular connective tissue. And that means that fibrocartilage is going to rely even more on the diffusion of nutrients from surrounding tissues that may be vascular And so what that means is that fibrocartilage is going to have a tendency to heal slowly, very slowly and so damages and injuries to fibrocartilage can really be detrimental to the health. Now, fibrocartilage is also going to be unique in that. In addition to its chondroblast and chondrocytes, it's also going to have some fibroblasts which recall, fibroblasts are cells of fibrous connective tissue or connective tissue proper. Again, another reminder of that can be the root fibro and fibrocartilage has some fibroblast. Now, these fibroblasts recall are going to be really important for producing the fibrous proteins in the extracellular matrix. And in fact, fibrocartilage is known for having very, very dense bundles of collagen fibers in the extracellular matrix. And because it has such dense bundles of collagen fibers, this actually makes fibrocartilage the strongest cartilage amongst the three different types of cartilage and fibrocartilage because it has so many dense bundles of collagen fibers, it's actually going to have relatively little ground substance in its extracellular matrix, especially in comparison to hyaline cartilage. Now, in terms of its functions, again, because it has such dense bundles of collagen fibers, it's going to have quite a lot of strength. And so in terms of its function, it will be able to resist both compression forces that comes with the bearing of weight from the body. And it's also able to withstand tension forces from stretching as well. And so in terms of body locations, we can expect to find fibrocartilage in areas of the body that need to be able to withstand lots of compression and tension. And so they actually can be uh found making up the intervertebral discs, which is the fibrocartilage found in between the vertebrae of our spine, which you can see over here in this image, notice that we're zooming in on the spine of this woman here and notice that in between the vertebrae of the spine right here in blue is where the fibrocartilage can be found. And again, it's very, very strong and so it can actually allow for shock absorption and cushioning. Now, it can also fibrocartilage can also be found in the niche of the knees and the Manish is really just the meniscus of the knee. Uh It's the plural version of the meniscus of the knee. And so in the knee, of course, that's in the lower part of our body and it needs to be able to withstand lots of compression forces since it's bearing the weight of our entire upper body pretty much. And so it's really important to have really, really strong fibrocartilage in the niche of the knee. And so notice down here, we have a micrograph showing you some fibrocartilage. And what you'll notice is that again, we're highlighting the chondrocytes within the lacuna, which again are those chambers that house the chondrocytes. There are also going to be chondroblast and some fibroblasts in fibrous cartilage as well. Fibrous cartilage has some fibroblast and the extracellular matrix, which you'll notice has really, really dense bundles of collagen fibers that are more regularly arranged, which is why it's more of a a blend between dense regular connective tissue and not so much dense, irregular connective tissue. Since the bundles of fibers are not totally randomly arranged in fibrocartilage. And so this here concludes our lesson on fibrocartilage and moving forward, we'll be able to apply these concepts and talk about the last type of cartilage in our lesson as well. So I'll see you all in our next video.

In this video, we're going to talk about the third and final type of cartilage in our lesson, which is elastic cartilage. And so elastic cartilage is actually quite similar to hyaline cartilage, except for the fact that as its name implies with the term elastic elastic cartilage is going to have significantly more elastic protein fibers in its extracellular matrix. And so in terms of its composition, once again, the ECM or the extracellular matrix is going to be filled with lots and lots of elastic protein fibers. And so recall from our previous lesson videos that elastic protein fibers are made from smaller proteins called elastin, which is an elastic protein that allows for elasticity, which recalls the ability to stretch significantly, but then equally as importantly, return back to its original shape after being stretched. And so elastic cartilage certainly is going to have elasticity. And so in terms of its functions, it's going to be able to help maintain the shape of structures while still providing great flexibility and elasticity. And so in terms of locations, example locations, elastic cartilage can be found in the external ear, which our external ear is quite flexible and stretchy and has that elastic ability where it returns to its original shape after stretching. And it can also be found in the epiglottis, which is a structure found in our throat area. And so notice here in this little image, we're zooming into the throat area here and you can see the epiglottis is this structure here. And the epiglottis is basically this little structure that access the flat to cover up our uh windpipe, our trachea as we're swallowing foods and drinks. So that those foods and drinks are directed down our esophagus and into our digestive system, instead of being directed down into our trachea and into our respiratory system. And so uh that epiglottis needs to have that elastic ability to be able to bend and stretch. But then again, return back to its original shape after bending and stretching. And again, elastic cartilage can be found in the external ear as well. Now, notice down below, we have a micrograph showing you elastic cartilage. And again, the main cell types are going to be chondroblast and chondrocytes. And notice we're indicating a chondrocyte within a lacuna which recall that the lacune are going going to be these chambers within the extracellular matrix that house chondrocytes. The extracellular matrix is going to be tough yet flexible, especially in elastic cartilage, which has lots and lots of elastic protein fibers allowing for elasticity. And like most cartilages in the body, elastic cartilage is going to be surrounded by a perichondrium, a layer of dense irregular connective tissue that is going to have uh that is going to be vascular and have blood. And so it is going to be able to support the avascular nature of the elastic cartilage. But again, because elastic cartilage is a vascular itself that is going to lead to slow healing. And so this year concludes our lesson on elastic cartilage and moving forward, we'll be able to apply these concepts and talk about other types of specialized connective tissue. So I'll see you all in our next video.

So here we have an example problem that asks how does the structure of fibrocartilage benefit its function in in intervertebral discs? And we've got these four potential answer options down below. And so option A says that large amounts of collagen bundles resist compression but allow flexibility. Now, this option seems reasonable, but let's skip it for now and check the other options. And so option B says large amounts of elastic fibers resist compression but allow flexibility. Now, recall from our previous lesson videos that fibrocartilage has an extracellular matrix made of really dense and thick bundles of collagen fibers and elastic fibers are not going to predominate in large amounts in the extracellular matrix. And elastic fibers are going to be more important for elasticity and they don't really allow for the resistance of compression forces like collagen fibers do. And so for those reasons, we can eliminate answer option B. Now, option C says adipocyte provide shock absorption. Now recall that adipocyte are fat cells that store fats or triglycerides as these relatively large lipid droplets within the adipocyte. And recall that adipocyte are mainly found in loose connective tissues such as adipose, connective tissue and ollar connective tissue, but these adipocyte are not going to be found in fibrocartilage. And so for that reason, we can eliminate answer option. C although fibrocartilage does have chondroblast and chondrocytes do recall that they do also have some fibroblasts, but again, they don't have any adipocyte or fat cells. Now, option D says chondrocytes provide shock absorption. Now, this is an interesting answer option, but it's important to note that it's not the cells that provide shock absorption. And again, the chondrocytes are the cells. It's mainly going to be the extracellular matrix that's produced by the cells that provides the shock absorption in the tissue. And so option D can be eliminated for that reason. And so of course, this means option A is the correct answer. And so fibrocartilage is going to have large amounts of collagen bundles in its extracellular matrix which allows it to resist compression forces, but also allows it to have a little bit of flexibility since collagen fibers have a little bit of flexibility as well. And so option A here is the correct answer to this problem. And again, those in intervertebral discs are in between the vertebrae or the bones within the spine. And so this year concludes this example and I'll see you all in our next video.

In this video, we're going to do a review of the three different types of cartilages. And so because this video is a review, really, there's no new information covered in this video that we haven't already covered in our previous lesson videos. And so if you're already feeling really good about the three different types of cartilages, then you can feel free to skip this video if you'd like. But if you're looking for a little bit of review, then stick around because this video could be really helpful for you. And so notice down below what we have is a table of the three different types of cartilages where in the first column, we indicate the particular type of cartilage. The second column has some key characteristics. The third column has some key functions and the fourth column has some example locations of where these cartilages can be found in the body. And so recall that the first type of cartilage that we covered in our lesson was hyaline cartilage. And so recall that hyaline cartilage is actually the most abundant cartilage throughout the entire human body. And it's also the weakest cartilage amongst the three different types of cartilages. Now also recall that hyaline cartilage is named for its appearance and the root heal. And hyaline cartilage is a root that means glass, which can be helpful to remind us that hyaline cartilage is going to have a very smooth and glassy appearance to it. Now, in terms of its extracellular matrix, it's going to have these very small or thin or fine bundles of collagen fibers. Now, of course, the collagen fibers are going to allow hyen Carli cartilage to be a very strong yet flexible tissue. However, because again, these are very small or thin or fine bundles of collagen fibers. Really, this is what makes hyaline cartilage the weakest of the three different types of cartilages. And also because they are small and fine and thin, that also makes them harder to see under the light microscope under regular staining techniques. And so if we take a look at this micrograph, you can see the cells within hyaline cartilage, including the chondroblast and the chondrocytes. And recall the chondrocytes are going to lie within these chambers called Laconi. And so you can see here uh throughout this tissue, these different chondrocytes lying within the Laconi chambers. Now, in terms of its functions, hyaline cartilage is again because of its smooth glassy appearance, it can actually reduce friction between bones as those bones are moving because of the muscles. And also because hyaline cartilage again, does have lots of collagen fibers, it is going to be a strong and flexible tissue. So it is going to allow for it to serve as a strong and flexible structural support. And also very notably of hyaline cartilage. It's actually a precursor to bone in the fetus. And so recall that the human fetus and human embryo actually have skeletons that are made almost entirely of hyaline cartilage initially. And then as the human develops, the hyaline cartilage in the skeleton is slowly replaced with bone over time. Now, in terms of the body locations where hyaline cartilage can be found, it can be found at the ends of bones where again, it can help to reduce the friction between bones. Uh again, it can serve as a strong and flexible structural support in areas such as the nose and the larynx or the voice box and the trachea or the windpipe. And again, it's associated with developing bones as well because again, hyaline cartilage makes up the vast majority of the fetus, the fetal skeleton and the human embryo skeleton. And again, it's slowly going to be replaced with bone over time. And so that's why it's associated with developing bones. And so notice that in these images, you can see that hyaline cartilage is indeed found at the ends of bones where it helps to reduce friction between bones. It's found in the larynx and the trachea. It's also found giving structural support to our nose and it can also connect the bones of our ribs to the sternum, which is our chest bone. Now, the second type of cartilage that we covered in our lesson recall was fibrocartilage and recall that fibrocartilage was actually an intermediate blend between hyaline cartilage and dense regular connective tissue. And recall that the root fibro can actually remind us of that because the root fibro can remind us of fibrous connective tissue, which is really connective tissue proper, more specifically dense regular connective tissue. And again, the cartilage part here reminds us that it's an intermediate blend between dense regular connective tissue and hyaline cartilage. Now, recall that fibrocartilage is unique in that it does not have a perichondrium around the cartilage and recall the perichondrium is a layer of dense, irregular connective tissue that is poorly vascularized but still supplies some blood vessels to support the avascular cartilage. Recall that all of these cartilages are avascular. Now, most highland cartilages are going to have a perichondrium but not all of them will. But fibrocartilage do not have any perichondrium. Also fibrocartilage. It it because it is this mixture between dense regular connective tissue and hyaline cartilage. It's actually going to have chondroblast chondrocytes and some fibroblast as well. And so those fibroblasts will help to create dense and thick bundles of collagen fibers which really gives fibrocartilage its strength. And so, fibrocartilage is actually the strongest cartilage amongst these three different types of cartilage. Now, it also is going to have very minimal or little ground substance in comparison to hyaline cartilage, for example. And so notice over here, we're showing you this micrograph of fibrocartilage. And in this micrograph, what you'll notice is that there are very dense bundles of collagen fibers in its extracellular matrix. And they're more regularly arranged than irregularly arranged in a random pattern which again helps to give fibrocartilage its strength. Now, in terms of its functions, it is going to be able to resist both compression forces from weight bearing uh from load bearing weights of the body. And it's also going to be able to resist tension forces from being pulled as well. And so we can find fibrocartilage in areas of the body such as forming the intervertebral discs between the vertebrae of our spine, which is what this image here is showing. You can see we're zooming into this woman's spine here and you'll notice that in between the vertebrae, uh this little blue layer that you see between them, that is going to be the intravertebral disc, which again is made mostly of fibrocartilage. And it can also be found in the men of the knee, which is really just the plural form of the meniscus of the knee. And again, that helps it to uh withstand the compression forces uh since our knees need to be able to uh basically bear the load of the weight of most of our upper body. Now, the third and final type of cartilage that we covered in our lesson was elastic cartilage. And so as its name implies, elastic cartilage is going to be very similar to hyaline cartilage, except it's going to have a lot more elastic protein fibers in its extracellular matrix. And so the ECM or the extracellular matrix is going to be filled with lots and lots of elastic fibers and recall that those elastic fibers are going to be made of smaller elastin proteins which allow for elasticity or the ability to stretch significantly. But then equally as importantly, return back to its original shape after being stretched. And so that's going to in terms of its function, uh elastic cartilage will help to maintain the shape while still providing great elasticity or flexibility. And so we can find elastic cartilages in areas of our bodies such as the external ear, which our ears are pretty flexible and have that elasticity. And we can also find it in the epiglottis, for example, which is the structure here in our throat that actually can move to block the passage of foods and drinks when we're swallowing. So that those foods and drinks are directed to our esophagus to go into our digestive system instead of going down into our trachea and into our respiratory system. And so this here concludes our review of the three different types of cartilages. And as we move forward in our course, we'll be able to get a little bit of practice and we'll also be able to talk about other types of specialized connective tissues as well. So I'll see you all in our next video.

True or False: The nose and the ear are made of the same type of cartilage.

• A. True: they are both hyaline cartilage. 
• B. True: they are both elastic cartilage.
• C. False: the nose is elastic cartilage and the ear is hyaline cartilage.
• D. False: the nose is hyaline cartilage and the ear is elastic cartilage.

Janine fell off her bike, cutting her knee and tearing the hyaline cartilage of her knee joint. At the doctor's office, she is told the cuts will heal in a few weeks, but the cartilage will take months. Using what you know about tissues, why does the cartilage take longer to heal?

• A. Cartilage is unable to regenerate because it lacks -blasts cells but epithelial tissue can regenerate. 
• B. Cartilage has limited blood supply while areolar tissue below the skin is vascular.  
• C. Cartilage has a more complex structure than epithelial or connective tissue proper, so it takes longer to heal. 
• D. The lacunae in cartilage make the healing process slower because the chondroblasts can't move.