capillary

(anatomy) any of the small and thin-walled branching blood vessels that connect the arterioles and venules

A capillary is the smallest blood vessel in the human body, consisting of a single layer of endothelial cells. Capillaries connect arteries and veins, facilitating the exchange of oxygen, nutrients, and waste products between the bloodstream and surrounding tissues. They play a crucial role in delivering essential substances to cells and removing metabolic waste. Capillaries have a large surface area due to their small size and extensive network, ensuring efficient exchange and supporting the proper functioning of every cell in the body.

a tube of small internal diameter; holds liquid by capillary action