What are the smallest blood vessels called?

The smallest blood vessels in the circulatory system are known as capillaries. These tiny vessels connect the arterial and venous systems and are essential for the exchange of substances between the blood and surrounding tissues. Capillaries are only one cell thick, which facilitates the diffusion of oxygen, carbon dioxide, nutrients, and waste products. Their small size and extensive network throughout the body allow for efficient transport and delivery of vital materials to cells while removing metabolic waste.

In contrast, veins are larger vessels that carry deoxygenated blood back to the heart, while arteries are blood vessels that carry oxygenated blood away from the heart. Venules are small vessels that collect blood from capillaries and lead it into veins, but they are larger than capillaries and not the smallest blood vessels in the body. This distinction makes capillaries unique in their size and function within the circulatory system.