in this video we're going to discuss a simple epithelium so uh epithelial tissue is subdivided into two large groups simple epithelium and stratified epithelium and simple epithelium means but we only have one layer of cells and because we have one layer of cells each individual cell sits on a basement membrane right so in simple epithelium each cell touches the basement membrane within simple epithelium we're going to distinguish four types and those four types are actually formed based on the shape of cells right so once we decided that we have one layer of cells we are then going to look at their shape so the first type of simple epithelium is called squamous and what squamous epithelium means is that again we have this basement membrane but cells that are sitting on this basement membrane are flat so a lot of times when we talk about simple squamous epithelium we refer to it as the cells look like fried eggs um in simple epithelium because we have this one layer of flat cells it makes it perfect for diffusion right so if we're trying to cross this layer we don't have a lot of distance but we have to cross those cells are pretty flat so squamous epithelium is best for diffusion which means that brings us to uh parts in the border locations in the body where diffusion is so important think about lungs that's where we're exchanging oxygen for carbon dioxide it has to happen pretty quickly and effectively we have a lot of that in the kidneys and that's because there is also a lot of transport that's happening in the kidney tubules and then we have two specific locations where this simple squamous epithelium gets um a um an individual name so the first one is called mesophilium and if you remember our discussion on serous membranes central squamous epithelium is going to line those serous membranes and if you remember that simple epithelium is going to produce the watery fluid right so there is some secretion that's associated with that in addition to mesophyllium we also have what's known as endophilia endothelial simple squamous epithelium that lines um the inside of blood vessels and the heart so um instead of saying simple squamous epithelium inside blood vessels or simple squamous equilibrium inside the heart if we use the term endothelium it is clear where the location of that epithelium is right so some of you may have heard about mesothelioma uh if you make that connection you're right on spots so tumors of this simple squamous epithelium one serous membranes lead to a type of cancer called mesophilia second type of simple epithelium and this one is called cuboidal and i think it's pretty self-explanatory but that because it's um it got gets the name cuboidal the cells are kind of square right so they're just as wide as they're tall and simple cuboidal epithelium is one of the types that can have some additional structures and those structures are microvilli if you remember from your readings microvilli are short finger-like extensions on each individual cell and their primary function is to increase surface area all right so simple cuboidal epithelium will be found in the kidneys so again the larger the surface area the more transport we can do and in addition to that we are also going to find it in certain glands uh and a couple of examples of this glance of the liver and the thyroid gland so um one of the functions that this simple cuboidal epithelium is doing is absorption right so we are moving solutes from the lumen into the bloodstream third type um simple columnar epithelium and again if we think about the name probably makes sense but this cells are taller when they are wide they look like columns and the simple columnar epithelium is also able to have microvili so right here you can have microvilli um so we'll do a couple of those but in addition to that um you also has a cell that is known as the goblet cell so let me make a cell in here so this is whole blood cell goblet cells produce mucus so it is the simplest example of an exocrine gland is just one cell and that cell produces this kind of viscous sticky product called mucus so where do we find simple columnar it is mostly seen in the digestive system so think stomach small intestine large intestine there is a lot of um transport mechanisms happening there so if it is absorption there is also secretion right because when making this mucus and then the last type is known as pseudo stratified and a lot of times students get this confused and they think if it says pseudostratified then that means we have multiple layers but in fact in pseudostratified epithelium all cells are actually touching the basement membrane only they tend to have different heights so they are nuclear are seen in different levels and it looks like it's stratified but it's not so pseudostratified means falsely stratified so falsely and in pseudostratified epithelium we have goblet cells so it's right here what blood cells which means we produce mucus but we also have vli oh sorry cilia and cilia are kind of longer extensions on the surface of the cell right microvillia are shorter sillier longer and on although we have silver but don't move on pseudostratified epithelium it is actually movable cilia and there has a lot of importance for the organ system where we find this hdtlm and that is the respiratory system so think about your airways where we have loads of small particles dust bacteria um that enter our lungs enter those airways and the cilia are able to move and the movement of cilia actually moves uh the um all these particles that gets stuck in the mucus produced by global cells it moves them upward into the throat where we can i just spit it out almost likely uh we're going to swallow it it enters the stomach and then it gets destroyed by the gas hydrochloric acid in the stomach so some of the functions here is secretions secretion so we produce mucus we're also able to move it so if we look at simple epithelium we know that one characteristic that combines all of us into one group is that one layer of cells where each cell is actually individually touching the basement membrane and then depending on shape we have four types squamous cuboidal and columnar pseudo stratified looking like it has layers but in reality it only has one