Stratified Epithelia

Stratified Epithelia

Stratified squamous epithelium

Stratified squamous epithelia vary in thickness depending on the number of cell layers present. The deepest cells, which are in contact with the basement membrane, are cuboidal or columnar in shape. This layer is usually named the basal cell layer, and the cells are called basal cells. Basal cells are mitotically active and replace the cells of the epithelium which are lost by "wear and tear". The basal cell layer is followed by layers of cells with polyhedral outlines. Close to the surface of the epithelium, cells become more flattened. At the surface of the epithelium, cells appear like flat scales - similar to the epithelial cells of simple squamous epithelia.
Remember that it is the shape of the cell which form the surface of the epithelium which gives the name to the epithelium.

Stratified cuboidal and columnar epithelia

are not common. A two-layered cuboidal epithelium is, for example, seen in the ducts of the sweat glands. Stratified columnar epithelia are found in the excretory ducts of the mammary gland and the main excretory duct of the large salivary glands.

Suitable Slides

stratified squamous epithelium: sections of the oesophagus, tongue or vagina - H&E, van Gieson, trichrome.
stratified cuboidal epithelium: skin (excretory ducts of sweat glands) - H&E
stratified columnar epithelium: sections of the parotid gland or mammary gland - H&E