Identify the structure at the arrow.

Identify the structure at the arrow.

• A. Microvilli
• B. Simple columnar epithelium
• C. Cilia
• D. PCCE

Answer: (C)

Cilia are long, hair-like extensions on the apical surface of certain epithelial cells. They are distinct from microvilli, which are shorter, finger-like projections that form a dense brush border to increase surface area. If you see a slender, whip-like projection protruding from the cell surface and often aligned to beat in a coordinated fashion, that’s characteristic of cilia. This structure is what you’d expect on epithelia such as the respiratory lining or fallopian tube, where cilia help move mucus or eggs along. The layer described as pseudostratified ciliated columnar epithelium refers to the type of epithelium that bears these cilia, not the projections themselves. Simple columnar epithelium describes the height and arrangement of the cells, not the presence of cilia.

Cilia are long, hair-like extensions on the apical surface of certain epithelial cells. They are distinct from microvilli, which are shorter, finger-like projections that form a dense brush border to increase surface area. If you see a slender, whip-like projection protruding from the cell surface and often aligned to beat in a coordinated fashion, that’s characteristic of cilia. This structure is what you’d expect on epithelia such as the respiratory lining or fallopian tube, where cilia help move mucus or eggs along.

The layer described as pseudostratified ciliated columnar epithelium refers to the type of epithelium that bears these cilia, not the projections themselves. Simple columnar epithelium describes the height and arrangement of the cells, not the presence of cilia.