What are basal cells in pseudo-stratified epithelia and their function?

• A. Small, undifferentiated cells near the basal layer that act as stem cells to renew and differentiate the epithelium.
• B. Large, secretory goblet cells near the apical surface.
• C. Ciliated cells responsible for movement of mucus.
• D. Fully differentiated squamous cells at the surface.

Answer: (A)

In pseudostratified epithelia, basal cells function as the stem-like progenitors that renew the tissue. They are small, undifferentiated cells located just above the basement membrane and divide to replace cells lost from the surface. Through division, they can generate the differentiated cell types that populate the epithelium, such as ciliated columnar cells and mucus-secreting goblet cells, ensuring the lining can be maintained and repaired.

This tissue often looks multilayered because cell nuclei lie at different levels, but every cell still contacts the basement membrane; the basal cells sit at the bottom as the source of new cells. Goblet cells near the apical surface are secretory and produce mucus, while the ciliated cells on the surface help move that mucus. Fully differentiated squamous cells at the surface would not be characteristic of this type of epithelium, which is why those options don’t fit as descriptions of basal cells.