Epithelial and Connective Tissue PDF

[00:00:06] >> This presentation contains a very brief overview of epithelial tissue, including attention to stratified squamous epithelium, which we will find in the integumentary system. And connective tissue, which addresses a broad variety of tissues including bone and cartilage, as well as conne...

[00:00:06] >> This presentation contains a very brief overview of epithelial tissue, including attention to stratified squamous epithelium, which we will find in the integumentary system. And connective tissue, which addresses a broad variety of tissues including bone and cartilage, as well as connective tissue proper that we'll talk about which addresses things like tendon and ligament. [00:00:38] Epithelial tissue divides into two major categories covering epithelium, which are things like the stratified squamous in our skin, as well as simple squamous in many other organ systems and glandular epithelium. The overall functions of epithelium, obviously providing protection such as in our skin. Epithelium can also help absorb in our digestive system. [00:01:04] It also has secretory properties, such as in some glands. There are also abilities for sensation and transport of molecules. Epithelial tissues are named and defined based on their layers, the shapes of the cells, and potential specialized features. When we talk about the layers in epithelial tissue, it could be stratified, which means many layers, or it could be pseudostratified, which means it actually only has one layer, but it appears to be multilayered. [00:01:40] Such as the pseudostratified columnar epithelium in our respiratory tracts. And it can also be simple, which essentially means one layer of cells. The shape of the cells is another part of our defining characteristics. So a squamous cell is going to be a very flat cell. A cuboidal cell really looks like a little dice, it's a square. [00:02:04] And then a columnar cell is going to be a cell that is essentially taller than it is wide. And finally, some tissues are named based on additional special features such as cilia, goblet cells if it's keratinized like our epidermis, or if it has microvilli. To prepare for examination of the integumentary system, we're going to give just a little bit more attention to our stratified squamous epithelium. [00:02:33] The major place that we find this is in our epidermis. And the reason for this is our are stratified squamous epithelium has many layers to it. And this allows protection, especially in our epidermis where there is keratin within the cells, which helps with waterproofing the body, essentially keeping all of our fluids from escaping. [00:02:58] So we will notice and we will look at the integumentary system in another lecture, but what you will see is stratified squamous epithelium shows many layers on top of each other of very flat cells. Connective tissue divides into many different categories. There's what we call connective tissue proper, and then there are other very specialized types of connective tissue. [00:03:28] These specialized types we actually identify as individual tissues, such as cartilage, which we will talk about in another lecture breaking down into three subtypes. We also see bone as a specialized connective tissue, and the blood and bone marrow are also considered connective tissue. We will focus today on loose connective tissue, or connective tissue proper, which includes our loose connective tissue and our dense connective tissue. [00:03:59] And finally, within dense connective tissue, we can break it down into two types. There is dense regular, which essentially means all of its fibers lined up in the same direction as we will see, and there's dense irregular, which means the fibers align in many different directions. All types of connective tissue have certain components. [00:04:22] First of all, connective tissue will contain cells. This is cells such as fibroblasts that are going to make our fibers, as well as mast cells, macrophages which are for immune process, and we also will see some fat cells. Again, all types of connectivity tissue will have fibers in them. [00:04:42] These are things like collagen that gives toughness as well as elastin which allows stretchiness, and reticular fibers which are what essentially make a framework to give structure to the tissue. Finally, we will see in all connective tissue extracellular matrix and this is essentially a fluid matrix that contains different types of proteins that also gives structure, and define the characteristics of the tissue. [00:05:12] We will next explore a couple types of connective tissue proper including loose connective tissue, and dense connective tissue. One type of loose connective tissue is your areolar connective tissue. A key place that we will find this is in the papillary layer of the dermis, which is essentially the upper layer of the dermis that lies between the deeper layer of the dermis and the upper dermis. [00:05:40] The key to this type of loose connective tissue is it allows for mobility of the more superficial tissue on the deeper tissue. Another type of loose connective tissue is our adipose tissue, which is essentially our fatty tissue. And this is a tissue that allows for some sort of packing around the organs, it also provides for insulation within the body, shock absorbing. [00:06:09] And this is essentially again a mobile tissue that has adipose cells within it that provide that cushioning, and insulation. As physical therapists, we will spend a lot of time working with dense regular connective tissue, because this is the tissue that's found in our tendons and ligaments. This type of tissue, the collagen fibers, act very much like a rope. [00:06:35] So what you will see in a histological slide is that all of the collagen fibers are lining up in the same direction. So dense regular connective tissue is very good at taking tension in one particular direction. And we will see this within our tendons, where it aligns with the muscle direction of pull, or the ligaments where those fibers align with the direction of tension that the ligament stabilizes. [00:07:04] Our final type of connective tissue for today is our dense irregular connective tissue. What that means is that your fiber direction in dense irregular connective tissue aligns in many different directions. This is evident in the dermis whereas our dense regular connective tissue worked well for tension in one particular direction. [00:07:27] Our dense irregular connective tissue can take tension in many different directions. This is very valuable in areas like the skin because our skin may be subject to forces from many directions.