How the Heart Works The Heart
The heart is an organ about the size of your fist that pumps blood through your body. It is made up of multiple layers of tissue.
Your heart is at the center of your circulatory system. This system is a network of blood vessels, such as arteries, veins, and capillaries, that carries blood to and from all areas of your body. Your blood carries the oxygen and nutrients that your organs need to work properly. Blood also carries carbon dioxide to your lungs so you can breathe it out. Inside your heart, valves keep blood flowing in the right direction.
Your heart’s electrical system controls the rate and rhythm of your heartbeat. A healthy heart supplies your body with the right amount of blood at the rate needed to work well. If disease or injury weakens your heart, your body’s organs will not receive enough blood to work normally. A problem with the electrical system — or the nervous or endocrine systems, which control your heart rate and blood pressure — can also make it harder for the heart to pump blood.