What is more complex a heart or circulatory system?

The circulatory system is more complex than the heart alone, as it encompasses a network of blood vessels, including arteries, veins, and capillaries, which work together to transport blood throughout the body. The heart functions as a pump within this system, driving the circulation of blood, but it relies on the intricate structure and function of the entire circulatory system to effectively deliver oxygen and nutrients to tissues. Therefore, while the heart is vital, the complexity of the circulatory system as a whole is greater.