What is the primary role of capillaries in the circulatory system?

The primary role of capillaries in the circulatory system is to exchange nutrients and waste with tissues. Capillaries are the smallest and most numerous blood vessels, creating an extensive network that permeates all tissues in the body. Their walls are extremely thin, typically just one cell thick, which allows for the efficient transfer of substances between the blood and surrounding tissues.

Through capillary walls, oxygen from the blood diffuses into nearby cells, while carbon dioxide and other waste products move from the cells into the blood to be carried away for elimination. This exchange of gases, nutrients, and waste is essential for cellular metabolism and overall homeostasis. The unique structure of the capillaries facilitates this process, making them crucial in ensuring that tissues are adequately supplied with the necessary nutrients while simultaneously removing metabolic byproducts.

The other choices refer to functions of different components of the circulatory system. For instance, while arteries do carry oxygenated blood from the lungs, their primary role is not linked to the nutrient and waste exchange, which is specific to capillaries. Similarly, while veins are responsible for transporting blood back to the heart, connecting them to arteries is a function associated more with the overall circulatory system rather than a role specifically attributed to capill