Which vessels are responsible for allowing oxygen and nutrients to be delivered to tissues?

Capillaries are the vessels that facilitate the exchange of oxygen, nutrients, and waste products between the blood and the tissues. They are the smallest type of blood vessel in the body, characterized by their thin walls, which are only one cell layer thick. This thinness allows for efficient diffusion; oxygen and nutrients in the blood can easily pass through the capillary walls and enter the surrounding tissues, while carbon dioxide and metabolic waste can move from the tissues into the blood.

While arteries also play a critical role in transporting oxygen-rich blood away from the heart to various body regions, it is the capillaries where the actual exchange process occurs. Veins, on the other hand, primarily return deoxygenated blood back to the heart, and venules are the small vessels that collect blood from capillaries but are not involved in nutrient and oxygen delivery themselves. Therefore, capillaries are vital for the direct delivery of oxygen and nutrients to tissues.