What are the main differences between simple, pseudostratified and stratified epithelia in terms of cell height and layering?

• A. Simple is one cell layer tall; pseudostratified appears multi-layered but is a single layer with nuclei at different heights; stratified has two or more true layers with varying cell heights.
• B. Simple is multi-layered; pseudostratified is single layer; stratified is pseudostratified.
• C. Simple is tall cells; pseudostratified is short cells; stratified is cuboidal.
• D. Simple has keratinization; pseudostratified is non-keratinized; stratified keratinized.

Answer: (A)

The main idea is how many cell layers there are and how tall the cells are. Simple epithelia are a single cell layer thick, with every cell touching the basement membrane, and the cells themselves can be flat, cube-shaped, or tall. Pseudostratified epithelia look like multiple layers because the nuclei are at different heights, but every cell actually contacts the basement membrane, so it’s still one layer. Stratified epithelia have two or more true layers, with only the deepest cells touching the basement membrane and the surface cells varying in shape depending on the region (often squamous at the surface in stratified squamous). Keratinization is not the defining feature here; it’s a property of some stratified squamous epithelia, while simple and pseudostratified differ in layering rather than keratinization.