Heart. Artwork showing the anatomy of the heart, a muscular pump. The vena cava (blue) returns deoxygenated blood from the body to the heart's right atrium (chamber, upper left). The blood flows in to the right ventricle (chamber, centre left), which contracts to push the blood through the pulmonary artery (purple) to the lungs. The tricuspid valve (pink) prevents the backflow of blood during the contraction. From the lungs, newly oxygenated blood enters the left atrium (below pulmonary artery) and flows to the left ventricle. The left ventricle contracts to push the blood to the aorta (red) and around the body. The mitral valve (pink) prevents backflow to the left atrium.