The heart is the engine that powers the body. It is the centre of the circulatory system, pumping oxygenated blood around the body in arteries and returning it in veins. The lub-dub of a heartbeat is the rhythm that underlies all of human life. Since the heart is so important to keeping a human body running, heart disease is deadly. Maintaining your cardiovascular health includes keeping an eye on your blood pressure and cholesterol levels, as well as getting plenty of exercise.