In this video we're going to provide a brief overview of connective tissue. (uh) We're going to start with some unique characteristics that connective tissue shares, and then we're going to talk about the components of this tissue. So we know that connective tissue is one of the four primary tissue types, of three being epithelial, nervous, and muscular. What makes connective tissue very unique is the fact that it is one of the most varied and widely distributed tissues in the body. So most varied and what that means is that in connective tissue we can see blood, which is fluid and fills blood vessels and the heart Or we can see bone, which is very solid and creates this framework and support for the entire body. It is also widely distributed. So as we talk about different types of connective tissue, we're going to see it in the skeleton, we're going to see it in the structure is associated with a skeleton; when I see it in the dermis, in tendons, and ligaments. So well throughout the body, we are going to find connective tissue. (uh) Connective tissue also has lots of matrix, and we'll talk more about the components of a matrix a little bit later, but this is all the extracellular material that we find in the tissue. (uh) What's unique to connective tissue is also the fact that it has different degrees of vascularization. So different vascularization. If you remember when we talked about epithelial tissues, we said they are avascular. Well with connective tissue, we'll see some that are well vascularized, some that are poorly vascularized, and some that are avascular altogether. Connective tissue also comes from the same source, same origin. (um) So during embryonic development we have a layer called mesoderm and this layer is going to give rise to mesenchyme and this is embryonic connective tissue that will give rise to all types of connective tissue. And finally connective tissue is of three types, of three subtypes of connective tissue. Here we're gonna have a fluid connective tissue, that will include the blood and the lymph. We're going to have fibrous connective tissue or connective tissue proper, that will include tissues like fat or tendons and ligaments. And then finally we are going to have supportive connective tissue, that will include cartilage and bone. So in this video we are going to discuss typical components of connective tissue, and we're going to create here three groups. (um) So we'll start with two, and then we'll divide it into three. And the first component of any tissue (um) is cellular components, so the types of cells that we see in the tissue. And then we're gonna have the matrix, which is the extracellular material. And then the matrix is composed of fibers and ground substance. So we'll start with the cells first and then we'll talk about ground substance and fibers as part of a matrix. So typically within connective tissues, we are going to see cells that are considered immature cells. And those immature cells are going to end in the ending "-blasts". So "-blast" for singular or "-blasts" for plural. And those would be immature cells. And those immature cells actually make the matrix. So as we talk about ground substance and fibers later on, it is very mature cells that will generate those components. So (uh) I'll provide a couple of examples here. For example, osteoblasts (um) so osteoblast, osteoblasts for plural, are immature cells in osseous tissue. Chondroblasts, chondroblast (um) is the immature cell in connective tissue. So osteoblast will generate (uh) the matrix of osseous tissue. Chondroblast will generate the matrix of cartilage. The second group of cells will be the mature cells, and they will end in "-cyte". So the mature cells do not make the matrix anymore, but they are responsible for maintaining the matrix. So those cells will usually be involved in maintaining the health of the tissue. So again a couple of examples here. Osteocytes So the osteocyte is the mature cell and osseous tissue. And chondrocyte (um) is the mature cell in cartilage. And finally we have an "other" category, so some additional cells that we find in a connective tissue with different functions. So we'll mention a couple of these cells here. Macrophages So we know that macrophages are heavily involved in phagocytosis. They're called cell wanderers because they're actually able to travel through the ground substance of connective tissue (um) and look for (um) maybe solids to engulf or get rid of cell debris and so forth. Neutrophils, which are a type of white blood cells and they are also involved in phagocytosis, but they particularly like bacteria. So bacterial phagocytosis. We're going to have mast cells. (uh) Mast cells produce a bunch of chemicals; we are only going to mention one and that is going to be histamine. So histamine is an important chemical produced during inflammatory responses. We have plasma cells. Plasma cells are going to make antibodies. And very important for protection, so antibodies can fight different infections. And then finally I'll do the last one, those are the adipocytes and adipocytes usually store lipids. They store it triglycerides and then we can use this lipids as a source of energy. So different types of connective tissue may have a different combination of the cells that we have here on the list. All right, so let's look at the ground substance of a matrix, and just as a reminder matrix is any extracellular material. So anything that we find in the tissue outside, the outside the typical cells. So ground substance is going to be different between different types. It can have a different texture. So for example, it can be fluid in blood, blood is a fluid connective tissue; it can be viscous if we're talking about fibrous or connective tissue proper; it can be rubbery (uh) if it's in cartilage; or it can be calcified and hard in bone. So generally speaking, when we talk about the components of a ground substance, we're going to concentrate on three of them. So the first one are the glycosaminoglycans, (um) so I am going to abbreviate them here as "GAG" or "GAGs" for plural. And an example of glycosaminoglycans are hyaluronic acid and chondroitin. (um) In fact there are four groups of glycosaminoglycans, we're mentioning just two of them because those are probably names that may be familiar to you. You know that we can buy a lot of over-the-counter supplements that have hyaluronic acid and chondroitin (um) alleging that they can help improve the health of our joints. So why are glycosaminoglycans important in ground substance? They provide the matrix with support. Glycosaminoglycans also have ability to hold electrolytes, and thus can also hold water. So this overall supportive function is mixed with this ability to hold other components like electrolytes and weapons [indecipherable]. Number two proteoglycans. And proteoglycans are kind of bottle brush molecules. And one of the importance for proteoglycans is to attach cells to each other, so attach cells to cells, and they're also going to help attach cells (I'm missing a t here) so attach cells to the matrix. And then finally adhesive proteins, and generally speaking, they kind of serve as the glue. So they help also attach cells to the overall matrix. All right, as we look at the types of fibers, we're also going to do three groups. So for group number one, we're going to put collagen fibers. So collagen fibers as I think it's pretty clear from the name are made of a protein known as collagen. And those collagen fibers provide the connective tissue with a very important function known as tensile strength. So what does tensile strength really mean? It has the ability to twist and stretch a little bit without breaking. So collagen fibers tend to be pretty thick and they don't tend to branch a lot. (um) We're gonna see a lot of collagen fibers in places like tendons, and we know the tendons connect muscle to bone; we're gonna see it in ligaments, those are connecting bone to bone; and then we're also going to see a lot of collagen fibers in the dermis of the skin. Group number two, reticular fibers. Reticular fibers are also made of collagen, however reticular fibers tend to be thin and extremely branching. And because of these properties, reticular fibers tend to create frameworks, stromas. So think about this as a skeleton of particular organs. So right here framework or stroma. And where we are going to see a lot of those reticular fibers, given their appearance and function, is in lymphatic organs. So for example, lymph nodes, or the spleen, or the bone marrow. When we talk about connective tissue proper, we actually have a subtype of connective tissue called reticular tissue, and it gets this name because the form it is formed of reticular fibers. And finally group number three and those would be elastic fibers. And elastic fibers are made of a protein known as elastin. And if you kind of think about the name of these fibers, they are responsible for elasticity; and what else testing is is our ability to stretch but when let go, return back to the original length. So a lot of times, this elasticity is misunderstood, it's not the ability to stretch, it is the ability to return back to normal after stretch. So those elastic fibers are going to be found extensively in such organs as the lungs, because remember we have to expand those lungs and then go back to the original shape and that helps us with breathing. We see a lot of elastic fibers in arteries, because they have to deal with changes in blood pressure . And then we're going to see some elastic fibers also in the dermis, and we know that when we lose some of those elastic fibers, which tends to happen with aging, our skin tends to sag. So (um) if we can summarize we talked about the components of connective tissue, we mentioned some unique characteristics that connective tissues have comparatively to other primary tissue types. We talked about the types of cells, so "-blasts" which are very immature, "-cytes" which are mature, and some other components; in addition to the two big parts of a matrix, the ground substance and the fibers