Classificatioon of epithelial cells?

Question

can any one give me "Classificatioon of epithelial cells and some examples of how structure relates to function.

Answer 1

Epithelia is one of four types of tissue. It is usually found on the edges and borders of things, and usually forms or lines open vessels. The cells tend to form a sheet, and are bound together very tightly. It is classified based on two things. First, is there a single layer of cells, or more than one? If it has a single layer, it's called simple; if more than one, stratified. Secondly, its name depends on the shape of the top layer of cells. They can be squamous (the cells are squashed flat, so often all you can see are the cell membranes, and sometimes a nucleus), cuboidal (basically as tall as they are wide, and the nucleui are round), or columnar (much taller than wide, and the nuclei are elongated ovals).
The type of tissue depends on fuction. For example, the stomach has stratified epithelium. The contents of the stomach are very acidic, and this tends to damage the top layer of cells, which get sloughed off. However, because the tissue is stratified (and the basal layer of cells reproduces very quickly), there is always another layer. Contrast this to the simple cuboidal cells that form the nephron tubules in kidney. Essentially, the kidney works on the "throw the baby out with the bathwater, then retrieve the baby" principle. The tubule walls have to be relatively thin so that our bodies can get back "the baby" (the things like sugar that went into the filtrate, but that the body wants to keep). They often have special pumps and transporters to move substances from the filtrate into the cells, and then back into the body.

Answer 2

Skin as well as all other organs. The circulatory system (blood vessels) have epithelial cells and all organs receive blood from these vessels. It's also found in the lumen of organs such as kidneys, stomach, large/small intestines, gallbladder, uterus, Fallopian tubes, bladder, etc.