What are capillaries primarily responsible for?

Capillaries play a crucial role in the circulatory system by acting as the interface between arteries and veins. They are the smallest blood vessels, and their primary function is to facilitate the exchange of gases, nutrients, and waste products between the blood and surrounding tissues. By connecting the arterial system, which carries oxygen-rich blood away from the heart, to the venous system, which returns oxygen-poor blood back to the heart, capillaries are essential for maintaining proper circulation and ensuring that the body's tissues receive the oxygen and nutrients they need while also aiding in the removal of metabolic waste.

This anatomical connection is fundamental to the functioning of the circulatory system. The other options, while they describe important functions of the cardiovascular system, do not accurately reflect the primary responsibility of capillaries. For example, transporting oxygen to the lungs is the role of the pulmonary arteries and veins, carrying blood away from the heart pertains to arteries, and regulating body temperature involves multiple systems, including the integumentary system, rather than capillaries alone.