Which statement about capillaries is correct?

• A. The capillary walls are thick and multi-layered.
• B. Arterioles lead into capillaries.
• C. Capillaries allow no diffusion of gases.
• D. Capillaries have no role in organ perfusion.

Answer: (B)

Arterioles lead into capillaries, delivering blood into the capillary beds where exchange with tissues occurs. The capillary walls are very thin—essentially a single endothelial cell layer—so gases like oxygen and carbon dioxide, along with nutrients and wastes, can diffuse across easily. This arrangement supports organ perfusion by delivering blood to all tissue areas and enabling cellular exchange. The other statements conflict with this role: capillary walls aren’t thick and multi-layered, diffusion does occur across capillary walls, and capillaries are central to tissue perfusion rather than having no role in it.