The heart works by using muscle tissue to pump blood between its four chambers, out to the lungs and out to the rest of the body, explains the American Heart Association. The heart uses valves to ensure blood flows in the correct direction as it pumps.
The four chambers of the heart are the left ventricle, the right atrium, the right ventricle and the left atrium, states the American Heart Association. The left ventricle pumps oxygenated blood through the aorta to supply the body. The deoxygenated blood then returns through the vena cava to the right atrium of the heart. The right atrium pumps the blood into the right ventricle, which in turn pumps the blood to the lungs via the pulmonary artery. Once the lungs reoxygenate the blood, it returns to the left atrium of the heart, which then pumps the blood to the left ventricle.
The pumping of the heart is controlled through electrical impulses generated within the heart, according to The Children's Hospital of Philadelphia. The impulses are generated in the sinus node of the heart, which acts as a natural pacemaker. It is usually located above the right atrium. The muscles of the heart contract as a response to the electrical impulses.