How do capillaries function within the cardiovascular system?

Capillaries play a crucial role in the cardiovascular system by facilitating gas and nutrient exchange between the blood and body tissues. Unlike larger blood vessels, which primarily transport blood to and from the heart, capillaries are tiny, thin-walled vessels that enable direct contact between blood and surrounding cells. This intimate proximity allows oxygen and nutrients present in the blood to diffuse through the capillary walls and enter the tissues, while waste products such as carbon dioxide and metabolic byproducts move from the tissues back into the blood to be transported away for elimination.

Their structure is specifically designed for this function; the walls of capillaries are only one cell layer thick, which enhances their permeability and efficiency in exchange processes. The large total surface area created by the vast network of capillaries in the body maximizes the opportunities for exchange, ensuring that cells receive the necessary substances for metabolism and that waste products are removed effectively.