Pseudostratified epithelium has how many true layers?

• A. 2 or more
• B. None
• C. 1, but looks like 2
• D. 3

Answer: (C)

The main idea here is how to define the number of true epithelial layers. True layers are based on whether every cell contacts the basement membrane. If all the cells touch the basement membrane, it counts as one layer, even if the nuclei sit at different levels.

Pseudostratified epithelium has cells of varying heights, so the nuclei are scattered at different levels and it looks multilayered under the microscope. But every cell rests on the basement membrane, so there is actually only a single layer of cells. The term “pseudostratified” reflects this illusion of multiple layers.

So the correct concept is that it has one true layer, yet it appears to have more than one layer. That’s why the description “one, but looks like two” best fits pseudostratified epithelium.