Epithelium that is made up of a number of layers of platelike (squamous) cells and is present in areas of the body that are subject to wear and tear. Stratified squamous epithelium containing keratin forms the outer layer of the skin; stratified epithelial cells that do not contain keratin are found in moist areas, such as the mouth and vagina. A pseudostratified epithelium, e.g. the ciliated cells of the mucous membrane lining the respiratory tract, consists of a single layer of cells whose nuclei are arranged at varying heights within the layer, suggestive of a truly stratified epithelium.