 The word squamous comes from squama which means scale Like the scales of reptiles or fishes Squamous epithelium is composed of flat cells the cells are as flat as scales That's why they are called squamous epithelium since the cells are so flat Substances can easily diffuse through them in both the directions and That's why they can be found in Capillaries and alveoli if you take a layer of squamous cells and roll it into a tube this is what it looks like and This is also what a blood capillary looks like the walls are composed of just a single layer of flat Squamous cells so this is very important for the function of capillaries because what do capillaries do they supply? Materials to tissues so capillaries go to every part of your body and they're responsible for supplying oxygen and Taking out carbon dioxide to the tissues and They also supply nutrients and take away waste products Now all this rediffusion is possible only because the wall of the capillary is so thin thanks to the squamous epithelium Similarly, if you look at the alveolus you can see that the wall is only one cell thick This squamous epithelium and that's important for the alveolus because That's a structure as you know is present in the lungs and that's where the air comes in and goes out So the alveoli are very closely associated with capillaries. So this here is also a capillary and Here it's mostly the exchange of gases So oxygen again So the oxygen in the alveolus that comes from the air breathing in our lungs that goes into the blood Capillary so that it can enter the bloodstream and go to different parts of the bodies and Similarly carbon dioxide that is there in the capillary that diffuses out into the alveolus So it can be breath out So both the alveolus and the capillary are one cell thick the squamous epithelium and hence this diffusion can happen So easily so in both of these cases the squamous epithelium is called simple squamous epithelium Simple because it consists of only one layer of cells. There is another type of squamous epithelium Which as you can see has many layers this type of epithelium is called stratified squamous epithelium Why stratified? Because the word strata Means layers So you must have guessed that diffusion of substances through this whole thing all these layers is quite difficult And that is indeed the case stratified squamous epithelium is not meant for diffusion Then what is it meant for it is meant for protection Which makes sense right because it has so many layers So it is kind of thick and even if let's say one or two layers from the top are peeled off somehow because of some Mechanical stress or some kind of chemicals the bottom layers are still there to protect the tissue beneath So now can you guess where this kind of epithelium is found? It's found in the skin and also other areas such as the buckle cavity That is the surface inside your mouth And if you look closely in the stratified squamous epithelium you can see that the top layers are indeed Flat like we saw in simple squamous epithelium But if you look at the bottom layers, they're not quite flat, right? They look more like cubes and still they're called squamous because the stratified squamous epithelium is named after only the top most layers and stratified squamous epithelium is also called Compound epithelium as opposed to simple epithelium Because it has many layers So we have looked at two types of squamous epithelium in this video simple squamous epithelium and stratified squamous epithelium The simple squamous epithelium is good for diffusion of substances Whereas stratified squamous epithelium is used mainly for protection