noun, plural: pseudostratified epithelia
The epithelial tissue (also called epithelium) is one of the different types of animal tissues. It is made up of one or more layers of cells closely packed together. It is primarily involved in protecting the underlying structures, secretion, regulation, and absorption. The epithelium may be classified based on the number of layers that make it up. In particular, the epithelium may be simple or stratified. In comparison, the simple epithelium is composed of a single layer of epithelial cells whereas the stratified epithelium is made up of a multiple layer of epithelial cells. However, there is a special type of epithelium called pseudostratified epithelium.
A pseudostratified epithelium is a simple epithelium. However, because of the manner that the epithelial cells are oriented along the basement membrane the tissue appears to be stratified. The epithelial cells are arranged in a way that the cells seem to be of varying heights but in actuality are about of the same height. The cells are too crowded that the nuclei are disposed at different levels. The pseudostratified epithelium is made up of columnar epithelial cells. It is rare that the cells that make it up are cuboidal or squamous in shape.
A pseudostratified epithelium may be further typified as either ciliated (with cilia) or non-ciliated (lacking cilia). Ciliated pseudostratified epithelium lines the trachea and parts of the upper respiratory tract. As for the non-ciliated type, it is exemplified by the membranous tissue lining the vas deferens.
- pseudostratified epithelial tissue