Answer
Heart, the key organ DeBakey centered his surgical expertise on, is a muscular structure central to the circulatory system, responsible for pumping oxygen-rich blood throughout the body and removing deoxygenated blood. His pioneering contributions in cardiovascular surgery, particularly in coronary artery bypass grafting, aortic aneurysm repair, and heart transplantation, revolutionized the field and saved countless lives, leaving a profound impact on modern cardiac care.