Which vessels are responsible for the diffusion of nutrients and oxygen to tissues?

Capillaries are the smallest and most abundant blood vessels in the body, specifically designed for the exchange of substances between the blood and surrounding tissues. Their thin walls, composed of a single layer of endothelial cells, facilitate the diffusion of nutrients, gases like oxygen and carbon dioxide, and waste products. This characteristic allows for efficient transport and exchange, enabling tissues to receive the essentials they need for metabolism and to dispose of harmful byproducts.

Veins and arteries are significant components of the circulatory system, with veins returning deoxygenated blood to the heart and arteries carrying oxygenated blood away from the heart. However, they do not primarily function in the exchange of substances with tissues; that crucial role is reserved for capillaries.

Lymphatic vessels serve a different purpose, primarily involved in the transport of lymph, which plays a role in immunity and fluid balance, rather than direct nutrient and gas exchange. Thus, capillaries are essential for facilitating the vital process of nutrient and oxygen delivery to tissues through diffusion.