Which tissue type appears multi-layered but each cell touches the basement membrane?

Which tissue type appears multi-layered but each cell touches the basement membrane?

• A. Pseudostratified epithelium
• B. Simple squamous
• C. Stratified squamous
• D. Transitional epithelium

Answer: (A)

The key idea is that some epithelia look like they have multiple layers even though every cell actually contacts the basement membrane. Pseudostratified epithelium fits this description: nuclei sit at different heights within a single layer of cells, so it appears multilayered, but each cell reaches the basement membrane. This is common in the trachea and other parts of the respiratory tract, where cells may be ciliated and include mucus-secreting goblet cells. In contrast, simple squamous is truly a single layer with all cells touching the basement membrane, so it isn’t multilayered. Stratified squamous has many layers but only the deepest cells touch the basement membrane. Transitional epithelium is layered and stretchable, but not all cells extend to the basement membrane, especially the surface cells. So the described pattern points to pseudostratified epithelium.

The key idea is that some epithelia look like they have multiple layers even though every cell actually contacts the basement membrane. Pseudostratified epithelium fits this description: nuclei sit at different heights within a single layer of cells, so it appears multilayered, but each cell reaches the basement membrane. This is common in the trachea and other parts of the respiratory tract, where cells may be ciliated and include mucus-secreting goblet cells. In contrast, simple squamous is truly a single layer with all cells touching the basement membrane, so it isn’t multilayered. Stratified squamous has many layers but only the deepest cells touch the basement membrane. Transitional epithelium is layered and stretchable, but not all cells extend to the basement membrane, especially the surface cells. So the described pattern points to pseudostratified epithelium.