So we want to look at simple squamous epithelium now and we're going to use a couple microscope slides to help us figure out what simple squamous epithelial tissue looks like and what some of its functions are. So again, simple squamous and to think about simple squamous epithelial tissue, I want you to think about a piece of paper to start with. If I have a piece of paper in front of me and in front of you, you can see as I hold it like this that it's a square piece of paper but you really can't tell if you're looking at it straight on if I'm holding one piece of paper or one entire rim of paper. But that's what we would call a frontal view or looking at the surface of the cell but consider what the edge of the piece of paper looks like. And if you were looking at that straight on you would just see a little sliver of the edge of the paper if I could hold it perfectly straight. Well, that's the way to think about simple squamous epithelial cells. So if we wanted to draw a simple squamous epithelial cell, we would just draw something that approximates the shape of a square and we would draw a circle in there maybe make it a little more oval shaped for the nucleus. So we've just drawn a simple squamous epithelial cell. But if we wanted to look at it in cross section or look at the edge of that cell, it would look something like this. This would be the nucleus of the cell. So we've pictured this piece of paper with something a little bigger than a golf ball attached to it and that would be similar to a simple squamous epithelial cell. This is just looking at it in cross section. So using the microscope over here I have a slide of a lung and we want to look at this lung slide. Now of course the lung is involved with gas exchange within humans and we take oxygen in and we exhale carbon dioxide. So within the lungs we see all of these little spaces. And if you look on this microscope slide you can see all these hundreds and hundreds of spaces. So those are the air sacs within the lungs called alveola. And the cells that make up these air sacs are simple squamous cells or simple squamous tissue is what the alveola are composed of. And if you think could picture the alveola you just picture sort of a little cluster of grapes perhaps and you have an air passageway leading into each little cluster of alveola. But instead of being a mate of grapes they're hollow on the inside and the skin so to speak or the covering is made of these simple squamous cells. Very very delicate tissue of course that's important for the respiratory gases to diffuse across the membrane. So we want to go up and look at this on a higher power. We can start to see the cells take shape when we look at it on 40X. And this is a pretty good microscope and I was able to get away with all immersion without putting all on it a second ago. And so here we can really see the cells that make up the alveola. And so here for example is an alveolas and we could go around and sort of trace some of these cells that we see. You see there's a square shaped cell with with the nucleus. And because these are all sort of mashed together in a hodgepodge it's hard to pick them out and just see cells where you're looking at them perfectly straight on. But I'm just picking out a few here that you may see in this area you can see no nuclei and that's just because of the way the slide was made. Now one important function of simple squamous epithelial tissue that we didn't mention when we were talking about epithelial tissues in general is diffusion. Because this tissue is so thin it makes it much easier for substances to move across that membrane by diffusion. For example if this was the inside of an alveolas and this was the outside then oxygen could move across that membrane or carbon dioxide can move in the other direction. So very thin tissue good for diffusion. Thank you.