Which organ is responsible for pumping blood through the body?

The heart is the organ specifically responsible for pumping blood throughout the body. It functions as a muscular pump that circulates oxygen-rich blood from the lungs to various tissues and organs while also returning oxygen-poor blood back to the lungs for re-oxygenation.

The other organs mentioned do play crucial roles in the body: the brain controls and coordinates many bodily functions including heart rate, the liver is involved in detoxification and metabolism, and the lungs facilitate the exchange of gases, but none of them are responsible for the actual pumping of blood. The heart's continuous contractions ensure that blood circulates effectively, supporting overall bodily functions and maintaining homeostasis. Therefore, it is central to the cardiovascular system, making it the correct answer to the question.