A simple epithelium has cells that form a single layer that are attached to the basement membrane. A stratified epithelium, on the other hand, consists of multiple layers of cells where only the basal layers are attached to the basement membrane.
The epithelium is one of the four major tissues in the body. It is made up of cells that are usually arranged in sheets or tubules that are connected to the underlying basement membrane. The epithelium serves as a covering for a number of internal and external surfaces of the body, and it can form glandular structures.
Different types of epithelia are classified according to the shape of the cells and whether or not the cells are layered. A simple epithelium may also appear as stratified and this type is classified as "pseudostratified epithelium." The cells that make up the epithelium are classified according to shape. These classifications are squamous (flat), cuboidal and columnar.