The inner lining of blood vessels and tissue involved in diffusion and filtration is formed by which tissue type?

• A. Simple cuboidal epithelium
• B. Stratified squamous epithelium
• C. Simple squamous epithelial tissue
• D. Connective tissue

Answer: (C)

A very thin barrier is needed for substances to move quickly between compartments, so the lining that handles diffusion and filtration is a single layer of flat cells. This is simple squamous epithelium. Its flat, thin profile creates the minimum distance for exchange, which is exactly what you want in places like the inner lining of blood vessels (the endothelium) and in structures where diffusion occurs, such as the walls of the lungs and parts of the kidneys. Because there’s only one cell layer, diffusion of gases, nutrients, and wastes happens rapidly.

Other tissue types aren’t suited to this role. Simple cuboidal epithelium is more involved in secretion and absorption and has a thicker profile. Stratified squamous is layered and designed for protection rather than exchange. Connective tissue isn’t a lining and doesn’t form a continuous barrier for diffusion.