So now that we've covered epithelial tissue in our previous lesson videos, in this video, we're going to begin our introduction to the second primary tissue in our lesson, which is connective tissue. Connective tissue is actually the most abundant and the most widely distributed tissue throughout the human body. We can pretty much find connective tissue in almost all areas of the human body. Connective tissue is also the most diverse tissue class amongst all four primary types of tissue, both in terms of its structure and its function.

Notice down below we are showing you these four micrographs that are all of connective tissues that we will get to talk more details about as we move forward in our course. But what you will notice is that just by looking at these four micrographs, you can clearly see that they are very different from one another. That goes to show how diverse of a tissue class connective tissue actually is. Notice the micrograph on the far left is actually showing us some connective tissue proper. The second micrograph is showing us some cartilage, which is also a type of connective tissue.

The third micrograph is showing us some bone, again, a type of connective tissue. And the fourth micrograph on the far right is showing us some blood, again, another type of connective tissue. We already know that our bones are really hard and solid structures, whereas our blood is actually a liquid.

This right here goes to show how diverse of a tissue class connective tissue actually is. However, despite all of the diversity of connective tissue, all connective tissues are going to have the following two things in common that we have numbered down below, number 1 and number 2. The first common feature of all connective tissues is that they are all derived from embryonic mesenchyme, which we covered briefly in some of our previous lesson videos. The second common feature of all connective tissue is that the cells of connective tissue actually occupy far less space than their ECM or their extracellular matrix, which takes up much more space in connective tissue. Unlike the cells of epithelial tissues, which we know from our previous lesson videos are really tightly packed or tightly pressed together with lots of tight junctions and desmosomes, and there's relatively little ECM between those cells, the cells of the connected tissue are not in direct contact with one another because they are spaced out or separated by the relatively large amounts of ECM or extracellular matrix.

In fact, connective tissue is unique amongst the four types of primary tissue in that the extracellular matrix can actually be significantly more prominent than the cells themselves. As we move forward in our course, we're going to talk more details about connective tissue. But this here concludes our introduction to connective tissue. In our next lesson video, we'll be able to focus on the structure of connective tissue. So I'll see you all there.