Epithelial tissue is used to line cavities throughout the body, as well as form your skin. The individual cells vary in size and shape and have different names. Their internal structures are mainly for supporting cell nourishment and protection. In the fetus, epithelial cells originate from mesoderm tissues and each cell is then programmed to where it will reside in the body. Epithelial cells can be keritinized or non-keritinized. Many, many cells are grouped together in layers of squamous, cuboidal, columnar, or transitional epithilial cells. There are specific areas in the body where these particular types of epithilial cells are found.