Certain epithelial cells are called pseudostratified columnar epithelium because :

Options

A. they have a layered appearance but all the cells contact the basement membrane
B. they are stratified and all the cells do not contact the basement membrane
C. their muclei are all located the same distance from the cell surface
D. they are a mixture of cell types

Answer

### Step-by-Step Solution:

1. **Understanding the Term "Pseudostratified":**
- The term "pseudostratified" is derived from two parts: "pseudo," meaning false, and "stratified," meaning layered. This indicates that the epithelium appears to be stratified (layered) but is actually a single layer of cells.

2. **Characteristics of Pseudostratified Columnar Epithelium:**
- Pseudostratified columnar epithelium consists of a single layer of cells that are of varying heights. This variation in cell height gives the appearance of multiple layers, hence the term "pseudostratified."

3. **Cell Arrangement:**
- In this type of epithelium, the nuclei of the cells are located at different levels within the tissue. This irregular arrangement of nuclei contributes to the illusion of stratification.

4. **Single Layer with Basement Membrane:**
- Despite the appearance of multiple layers, all cells in pseudostratified columnar epithelium are anchored to a single basement membrane, confirming that it is indeed a simple epithelium.

5. **Conclusion:**
- Therefore, pseudostratified columnar epithelium is termed so because it appears to be stratified due to the varying heights of the cells and the positioning of their nuclei, while it is actually a single layer of cells.