This epithelium has 40 to 50 layers of cells. They change shape as they migrate from the basal layer to surface: cuboidal cells in the basal layers, round cells in the middle layers, and flattened (squamous) in the upper layers.
The epithelium is separated from the underlying connective tissue by a thin basement membrane. It is seen as a dark band beneath the epithelium.
Keratin is not necessary because this epithelium is not exposed to the desiccating effects of air and is constantly kept moist.