Home | Heart Work | Getting Blood to the Body
The heart pumps blood to the lungs and to the rest of the body using an organized sequence of contractions of its four chambers. The pumping action is coordinated by electrical impulses provided by a natural "pacemaker". The coordinated pumping action gives rise to the characteristic heart beat. Emotional reactions and hormones affect the pacemaker, allowing the heart to speed up or slow down in response to varying demands.
The right atrium (upper heart chamber) receives dark, oxygen-poor blood from the body via large veins (the superior and inferior vena cava). The blood passes from the right atrium via an one-way valve to the right ventricle (lower heart chamber). The right ventricle pumps this blood to the lungs via a large artery (the pulmonary artery). In the capillaries of the lungs, carbon dioxide is removed and oxygen is picked up. The bright red, oxygen-rich blood returns to the left atrium. The blood passes via a one-way valve to the left ventricle, and from here it is pumped out through a large artery (the aorta) to be distributed to all parts of the body.
The arteries divide into smaller and smaller branches to supply tiny capillaries that run throughout the tissues of the body. In the capillaries, oxygen is passed from the blood to the tissues and carbon dioxide is passed from the tissues to the blood. The oxygen-poor blood then starts on its journey through the veins back to the heart.