Pseudostratified epithelium



A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia. As it rarely occurs as squamous or cuboidal epithelia, it is usually considered synonymous with the term pseudostratified columnar epithelium.

The term pseudostratified is derived from the appearance of this epithelium  in section which conveys the erroneous (pseudo means false) impression that there is more than one layer of cells, when in fact this is a true simple epithelium since all the cells rest on the basement membrane. The nuclei of these cells, however, are disposed at different levels, thus creating the illusion of cellular stratification. Not all ciliated cells extend to the luminal surface; such cells are capable of cell division providing replacements for cells lost or damaged.

Examples

 * Ciliated pseudostratified columnar epithelia are found in the lines of the trachea as well as the upper respiratory tract.


 * Non-ciliated pseudostratified columnar epithelia are located in the lining of the male urethra.

If a specimen looks stratified but has cilia, then it is a pseudostratified ciliated epithelium, since stratified epithelia do not have cilia.