The heart The organ that pumps the blood around the body in the circulatory system is the heart. The heart is a muscular organ located in the thoracic region of the body. The heart has 4 chambers, 2 atria, and 2 ventricles. The mitral valve separates the left atrium from the left ventricle. The tricuspid valve separates the right atrium from the right ventricles.
An interventricular septum separates the right ventricles. The left atrium receives oxygenated blood from the pulmonary vein and transport that to the left ventricle which contracts to pump blood in the great vessel called the aorta. Through the aorta, other vessels get oxygenated blood. The right atrium receives deoxygenated blood from the superior and inferior vena cava and it empties into the right ventricle. The right ventricle empties into pulmonary arteries which go to the lungs to get oxygenated.