Pseudostratified epithelium is composed of at least two types of cells: columnar cells, which reach the apical surface, and basal cells, which do not. Both, however, are in contact with the basal lamina, which is the interface between the epithelial layer and the connective tissue. Their nuclei are located at different levels in the epithelial layer. Depending on the number of epithelial cells, it may have two or more rows of nuclei, so that it can be wrongly taken as stratified epithelium, that is why it is named pseudostratified. Two rows of nuclei are found in some glandular ducts and in the epididymis.
Usually, cells that reach the free surface have cilia, such as in the respiratory ducts, or stereocilia as in the epididymis. However, some columnar cells may have no apical specializations as in the terminal portion of the male urethra.