in this video we're going to discuss the common characteristics of epithelial tissue so if you remember epithelial tissue is one of four primary tissue types and it has an unique characteristics that separates the epithelial tissue from the other tissues within the primary group um so we're going to mention those characteristics and we're going to describe a little bit of the influence on the functioning of epithelial tissue so we already know that epithelial tissue is highly cellular a lot of times epithelial tissue forms those linings or coverings and creating those barriers is important in having those densely packed cells one next to each other with very little matrix in between another characteristic of epithelial tissues is that they all have a basement membrane so what is this basement membrane really about basement membrane is made is a layer of connective tissue that underlies all epithelial tissues so let's say those are the tissues these are the cells of epithelial tissue and the cells are attached or anchored on to this basement membrane um so the basement membrane um usually reinforces the epithelial tissues we're going to write reinforces the epithelial tissue and it helps with the barrier function that we mentioned before because of the presence of this basement membrane epithelial tissues exhibit polarity we are not going to see it in any other tissues so uh please pay attention to that the polarity means that we have two poles right uh kind of like a battery so in the battery we have a positive pole and a negative bone there on the opposite sides of each other well in epithelial tissues those cells also have a pole and if you think about this there is really a top and there is a bottom for cells in epithelial tissue and this is not something we see in other tissues so the part of the cell right that's oriented towards the basement membrane this part this is one pole of the cell right and this part is called the basal surface basal surface so either of a part of a cell that sits on the basement membrane or the part of the cell that's oriented towards the basement membrane right because we can have um epithelial tissues with multiple layers so where is the basal surface then well this one is still oriented towards the basement membrane right so that's the basal surface the opposite of a basal surface is going to be the epical surface okay so this part this is the ethical surface so again kind of in layman terms we have the top and we have a bottom with other tissues we are not going to be able to distinguish that the next one will mention is tight junctions so as we think about epithelial tissues forming windings right so this is the basement membrane and then we have the cells um located here those tight junctions are formed between individual cells right so right here proteins in the plasma membrane of adjacent cells are going to fuse together and what tie junctions are really good for is because they create this think of a name tight right the space between those cells is so tight but certain solutes cannot pass through right so again goes back to that lining impermeable barrier function that loads of epithelial tissues have number five epithelial tissues are a vascular so let's kind of break this word down letter a the beginning of a word means absent okay and then if we look at the root vasc it means vascular blood vessels and so epithelial tissues do not have their own blood supply and that's kind of hard to wrap our head around but the best way to imagine that is think about having a very superficial paper cut if that paper cut only goes through a superior layer of skin by epidermis so epithelial tissue does not pass into the dermis it is not going to bleed right so epithelial tissues are vascular and that has implication for the connective tissue below because besides the basement membrane most of the time what we see under epithelium is loose connective tissue very well a type uh because epithelial tissue is going to rely on this connective tissue for nutrients and then for the removal of waste because it doesn't have its own blood supply number six epithelial tissues have high capacity for regeneration what does it mean um that means that a lot of epithelial cells will undergo um rapid mitosis and we will be able to replace the damaged cells or the cells that are worn out with new cells um if we think about cells epithelial cells in the lining of a stomach for example we have acidity we can go down to 1.52 on the ph scale so a lot of those cells are being destroyed but because this epithelial tissue can quickly replace them that barrier lining function is preserved and then finally innervated we have lots of nerve endings in epithelial tissues one of the functions that epithelial tissue serve is a sensitive function right so we are able to send signals um to the control center to the nervous system about changes that are happening in the body and that happens because we have loads of nerve endings coming to epithelial tissues