What organ is responsible for circulating blood throughout the body?

The heart is the organ responsible for circulating blood throughout the body. It functions as a muscular pump that moves blood through a network of arteries, veins, and capillaries. The heart's rhythmic contractions ensure that oxygen-rich blood is delivered to the tissues and organs while also returning deoxygenated blood to the lungs for oxygenation. This process is critical for maintaining bodily functions, supporting metabolism, and keeping all organs functioning optimally.

In contrast, while the brain plays a crucial role in controlling many bodily functions, including the heart's pumping action through the nervous system, it does not circulate blood itself. The liver is involved in processing blood and detoxifying substances but does not directly contribute to blood circulation. The kidneys are primarily responsible for filtering blood and maintaining fluid balance, rather than circulating it. Thus, the heart's unique role as the central pump in the circulatory system makes it the correct answer.