The heart is a muscular organ localized in the mediastinum. By function, the heart is divided into four chambers. Two upper chambers are known as the right and left atrium and two lower chambers are known as the right and left ventricles. The right heart acquires blood coming from the body through the superior and the inferior vena cava. It pumps back blood to the lungs through the pulmonary artery and the left heart receives saturated blood from the lungs.