The heart
The heart is a muscle about the size of your fist. It pumps blood around your body and beats approximately 70 times a minute. After the blood leaves the right side of the heart, it goes to your lungs where it picks up oxygen.
The oxygen-rich blood returns to your heart and is then pumped to the body's organs through a network of arteries. The blood returns to your heart through veins before being pumped back to your lungs again. This process is called circulation.
The heart gets its own supply of blood from a network of blood vessels on the heart's surface called coronary arteries.