In this video, we're going to begin our introduction to connective tissue proper, which recall from our previous lesson videos is one of two major classes of connective tissue in our lesson, the other being specialized connective tissue. Connective tissue proper is a collective term to refer to both loose connective tissue and dense connective tissues. Connective tissue proper including both loose and dense connective tissues are actually found all throughout the entire human body in various locations as we'll get to learn more about moving forward in our course. Connective tissue proper is going to be very rich in terms of the protein fibers found in the extracellular matrix. These protein fibers are often pretty distinct and easily seen under a light microscope, which is why sometimes connective tissue proper is also referred to as fibrous connective tissue.
Now, in terms of the functions, connective tissue proper has many different functions. These functions tend to be more generalized functions that apply to multiple body systems, multiple areas of the body, and multiple body processes. This generalized nature is why sometimes connective tissue proper is also referred to as general connective tissue. Loose and dense connective tissues are actually made from relatively the same types of cells and made from the same exact protein fibers. However, loose and dense connective tissues are actually going to differ from each other in terms of the amounts and the arrangements of those protein fibers in the extracellular matrix.
If we take a look at our image down below, notice we're showing you a map of our lesson and how we can organize connective tissue into two major classes. Again, they can be organized into connective tissue proper or general or fibrous connective tissue, and they can also be organized into specialized connective tissues. We'll talk about the specialized connective tissues later in our course. For now, we're focusing on connective tissue proper, which always includes loose connective tissue and dense connective tissue. As their name implies, loose connective tissue is going to have loosely spaced protein fibers in the extracellular matrix.
These loosely spaced protein fibers are going to be separated by a relatively large amount of ground substance. Notice below, we're showing you a micrograph of some example loose connective tissue forming the layer under the epithelia. What you'll notice about this micrograph of loose connective tissue is that these darker spots that you see throughout represent the nuclei of cells. All of these lines going through the image represent the protein fibers, which again are pretty distinct and clearly seen here in this micrograph. These protein fibers are pretty loosely arranged in such a manner that you can actually see these small spaces or holes in between these protein fibers, showing that loose arrangement of loose connective tissue. Dense connective tissue, as its name implies, is going to have more densely packed protein fibers in the extracellular matrix, with less ground substance in comparison to the ground substance of loose connective tissue. Notice here we're showing you a micrograph of some example dense connective tissue forming tendons and ligaments. What you immediately notice is that these pink fibers that you can see in this image are really densely packed together. You don't really see those open spaces like you did over here in this micrograph with loose connective tissue and their loose arrangement of those fibers. You can see how densely packed the fibers are in this particular tissue.
This here concludes our brief introduction to connective tissue proper. As we move forward in our course, we'll be able to learn a lot more about connective tissue proper and apply these concepts in problems. I'll see you all in our next video.