Heart, artwork. The heart is a hollow muscle that pumps blood around the body.The human heart beats an average of 72 times per minute. It has four chambers, made up of two atria and two ventricles.
The atria receive blood into the heart, and then pass it into the ventricles where it is pumped out again. Deoxygenated blood from the body is returned to the heart’s right atrium (chamber). The blood flows into the right ventricle (chamber), which contracts to push the blood through the pulmonary artery to the lungs. From the lungs, newly oxygenated blood enters the left atrium and flows to the left ventricle. The left ventricle contracts to push the blood to the aorta (arched, top) and around the body. Valves between the chambers prevent the backflow of blood.