this lecture is going to cover epithelial tissue that we're going to do a quick comparison between epithelial connective to very abundant tissues in the body epithelial tissue is going to be very tightly packed cells with very little extra cellular material around it when you look at this picture you see fibers running through the tissue and lots of space surrounding the fibers and cells the cells are not tightly packed as they are in epithelial tissue all epithelial tissue is going to have general characteristics that not only make it easy to recognize but also understand some of the functional traits all epithelial tissue has a free surface meaning that there's always one side that doesn't touch anything epithelial tissue will always sit on what we call a basement membrane which has two different layers one layer is where the Hemi desmosomes attach so the basal surface of the epithelial tissue will be attached to the basal lamina of the basement membrane by Heaney desmosomes connective tissue is always found beneath epithelial tissue and as we can see this blood vessel here does not penetrate the basement membrane so epithelial tissue is a vascular without blood vessels so it is a living tissue which means it needs nutrients and nutrients travel a body through blood so there has to be a way for us to get that material from the connective tissues blood vessels into the epithelial tissue and this occurs through diffusion the epithelial tissue will get its nutrients from diffusion of the blood vessels in the connective tissue but think about if you get a small paper cut most of the time you don't bleed and you don't bleed because of the lack of blood vessels epithelial tissue is a vascular however you do feel that paper cut it definitely stinks and that's because epithelial tissue has a great nerve supply so we say that it's innervated now anytime you do get a small cut over time you heal an epithelial tissue has a great ability to undergo mitosis and this is called proliferation so epithelial tissue is a vascular without blood vessels innervated great nerve supply and proliferative which means it can go through rapid mitosis when we talk about epithelia it's always gonna be named in a similar fashion we look at how many layers of cells are attached to that basement membrane and what does it cell shape that sits on the basement membrane so we have three layers simple means that there's only one layer of cells attached to the basement membrane stratified means there's two or more layers and then pseudostratified means that the cells are all attached to the basement membrane but since they are different heights it appears that there's more than one layer but in reality pseudostratified only has one layer of cells in the basement membrane regardless of how many layers the apical surface is always going to be present so simple apical surface pseudostratified and apical surface and then stratified in this particular picture there's about four layers and we still have that apical surface after you look at layers you're gonna look at cell shape in squamous they are very flat and thin when you look that at them from the side view but when you look at them from the top view they're what we call a morphic they don't have any particular shape so they're just a typical cells I kind of think they look like fried eggs cuboidal they're gonna be cube-like cells the nucleus is gonna be nice and round in the center and then columnar are gonna be column like in columnar we're gonna have an oval nucleus towards the bottom now what's unique about columnar tissue is that columnar tissue will often have some other specific characteristics that we don't see anywhere else and one of the things that columnar tissue will have is on top we're often going to see cilia and the cilia are going to be these long hair like structures that move back and forth and when they move back and forth they could be moving anything from mucus debris eggs so cilia can be on columnar tissue also on columnar tissue there could be little bitty short projections that kind of just look like a furry brush border and these are known as micro villi if micro villi are present cilia will not be present and microvilli are going to absorb nutrients so we're gonna find micro villi in your GI tract now columnar tissue doesn't have to have cilia our micro villi but the columnar tissue that we will discuss in the class will have one or the other the other thing that's unique to columnar tissue is that columnar tissue has goblet cells and goblet cells are specialized glands that produce mucus so if you are thinking about columnar tissue most of the time goblet cells will be present and they will be able to produce mucus then the cilia have the ability to move that mucus back and forth now when we look at these names of layers and cell shape there's a few things that you can think about any tissue that's going to be considered simple is gonna be great for diffusion osmosis filtration and absorption because it's only one layer that the material needs to move through does that mean that can't happen to stratified no it's just going to be not its primary function because we have so many layers to move material through so stratified in general are going to be used for protection so I want you to take a second and I want you to look at this middle cuboidal picture and I want you to think about how many layers it is then you want to name it by the cell shape so take one second pause it and think about the naming of this I hope you paused and if you said that this had one layer you're correct so it would be simple and when you look at the cell shape it's cuboid also you would say simple cuboidal okay when we look over here at the columnar tissue let's look at the two that I drew the cilia on how many layers do you see what is the shape of the cell and what is on top of these layers so pause it think about that for a second if you paused it how many layers did you say simple great the shape columnar and then since it has cilia on top you need to put that in the name so you can say ciliated simple columnar simple ciliated columnar as long as you get those words down you're doing a great job now once you name a tissue it often helps you with function as well as location but in general epithelial tissue you can have lots of different functions we find epithelial tissue lining and covering surfaces as well as the body so pretty much anything that has a hole in the middle which we often call lumens R has nothing around the outside of it that's because it's lined by epithelia epithelial tissue will also form the glands in your body so we often internment and flange alert epithelia and then epithelial tissue forms in most of your body's membranes and membranes are just sheets of tissues that line structures but have very specific functions so we're going to start off talking about the different types of tissues in the body so we're going to start discussing simple tissues so as you can see we have simple squamous and just like all the other tissue that's epithelia the simple squamous is gonna be sitting on your basement membrane beneath the basement membrane we have connective tissue and remember that all epic ladies use a vascular so that blood vessel will not penetrate the basement membrane now since simple squamous is very thin cells what do you think a good function for this tissue would be if you said diffusion osmosis filtration you're on a great start because it's so thin it's easy for material to move in and out of it now simple squamous is often called mesothelium our endothelium and the reason it's called this is based on its location so a lot of times we hear that there's two types of simple squamous mesothelium and endothelium however that's just because their location differs they're actually going to look the exact same so we'll start off with mesothelioma mesothelium is simple squamous that will line the outside of your structures of your organs so if you remember in Chapter one we discussed body cavities and we talked about how the body cavities on the front of the body the ventral side or line by serous membranes basically a serous membrane is just simple squamous mesothelium so what happens is simple squamous is going to touch the outside of an organ and that's going to form the visceral layer of the serous membrane and then simple squamous is going to actually form a pouch or a cavity around that organ and that's gonna be your parietal serous layer now depending on which way you see it it's gonna change the appearance so from this top picture where it's named peritoneum this is just telling us the cavity the peritoneal cavity is the one that surrounds your abdominal pelvic organs and from a top view it looks like a lot of fried eggs but it's only one layer from this top of you you can't actually see the thickness of it but you can see that your regular shape so again I think of simple squamous from the top view as a fried egg collection but simple squamous from the side view almost just looks like pancakes our sausage links together we see that we have the free surface and then we see that we have this transition and appearance or all of this pinkish this is all connective tissue that dark lining on top that is the simple squamous cells both of these are lining the outside of organs so both of these because that are mesothelioma but we also have endothelium endothelium is still simple squamous and as we can see from the side view this simple squamous is gonna still be flat and then it's gonna be found lining the inside of structures so simple squamous that lines the inside of structures is termed endothelium so we'll find it lining the inside of your heart inside of kidney tubules inside of blood vessels so endothelium and mesothelioma are both simple squamous they look super similar the difference is their location that is the main difference next the simple cuboidal remember we always have the basement membrane the simple cuboidal self sit on it and they're attached by Heaney desmosomes and then they're sitting on top a connective tissue that has blood vessels simple cuboidal main function is going to be absorption and filtration so we find these in urinary tubules so basically kidney tubes and what we can see is here's the basement membrane following my cursor this is connective tissue beneath that here's one cell and then here's the apical surface whoops you can also find simple cuboidal covering the outside of ovaries now the next tissues are going to be your columnar tissues so I have these pictures up there together so you can compare they're both simple columnar but one of them has long hairs on top so this is the ciliated simple columnar the other one is just gonna have short brush borders known as micro villi notice that both simple columnar are going to have goblet cells which produce the mucus they're both sitting on a basement membrane with connective tissue underneath it but since one has cilia we have to name it ciliated simple columnar whereas this one has micro villi so we can either call it non ciliated simple columnar Artem's to make it really simple you just call it simple columnar so here's a picture of simple columnar we're going to find