What are the smallest blood vessels responsible for the exchange of oxygen and nutrients called?

The smallest blood vessels that play a crucial role in the exchange of oxygen and nutrients are called capillaries. These microscopic vessels connect arteries and veins, creating a complex network throughout the body's tissues. Capillaries have very thin walls composed of a single layer of endothelial cells, allowing for efficient diffusion of oxygen, carbon dioxide, nutrients, and waste products between the blood and surrounding tissues. This exchange is vital for maintaining the body's cellular functions and overall health.

In contrast, arteries are larger vessels that carry oxygen-rich blood away from the heart to the rest of the body but are not involved in direct nutrient exchange. Veins are responsible for returning deoxygenated blood back to the heart; they also do not facilitate the exchange of substances at the tissue level. Venules are small vessels that collect blood from capillaries and flow into veins, but like veins and arteries, they do not conduct the exchange process that occurs specifically in capillaries.