What are the tiny thin-walled blood vessels that allow tissues to receive nourishment and eliminate waste products called?

Capillaries are tiny, thin-walled blood vessels that serve as the critical junctions between the arterial and venous systems. They are uniquely structured to facilitate the exchange of nutrients, gases, and waste products between the blood and surrounding tissues. The walls of capillaries are only one cell thick, which allows for efficient diffusion of oxygen and nutrients into tissue cells while simultaneously enabling the removal of carbon dioxide and metabolic waste products. This role is vital for maintaining the health and function of tissues throughout the body.

In contrast, veins are responsible for carrying deoxygenated blood back to the heart, while arteries are responsible for carrying oxygenated blood away from the heart to various parts of the body. Arterioles, on the other hand, are small branches of arteries that lead to capillaries but do not provide the direct exchange process that capillaries do. Thus, capillaries are the specific vessels essential for nourishing tissues and eliminating waste, making them the correct answer.