What are very tiny blood vessels that allow the exchange of nutrients and gases with tissues?

Capillaries are the very tiny blood vessels that facilitate the exchange of nutrients and gases between the blood and surrounding tissues. Their thin walls, composed of a single layer of endothelial cells, allow for easy diffusion of oxygen, carbon dioxide, and other substances. This extensive network of capillaries ensures that all cells in the body receive the nutrients they need while also removing waste products.

Arterioles and venules play a role in the circulatory system but do not perform the same function as capillaries. Arterioles are small branches of arteries that lead to capillaries, while venules are small veins that collect blood from capillaries and carry it toward larger veins. The aorta, on the other hand, is the largest artery in the body, distributing oxygen-rich blood from the heart to the rest of the body. Therefore, the unique structure and function of capillaries make them essential for the exchange process at the tissue level.