Which type of blood vessel is characterized by being very small and facilitates the exchange between blood and body cells?

• A. Artery
• B. Capillary
• C. Vein
• D. Aorta

Answer: (B)

Capillaries are small blood vessels that play a crucial role in the circulatory system by facilitating the exchange of oxygen, nutrients, and waste products between blood and the surrounding tissues. Their thin walls, typically just one cell thick, allow for efficient diffusion of substances. This unique structural characteristic makes capillaries particularly suited for their function, as they provide a large surface area relative to their volume, enabling effective interactions with body cells.

In contrast, arteries are larger vessels that carry oxygen-rich blood away from the heart, while veins are responsible for returning deoxygenated blood back to the heart. The aorta, as the largest artery in the body, is specifically designed to handle high-pressure blood flow from the heart but does not participate in the direct exchange process that capillaries do. Therefore, the distinct function and structure of capillaries confirm their critical role in nutrient and gas exchange at the cellular level.