Your heart has two jobs. It pumps blood in need of oxygen to the lungs and it drives newly oxygenated blood to the rest of the body. Amazingly, your heart performs both of these tasks simultaneously by squeezing the left and right atrium and then the left and right ventricle. Let's take a closer look at this multi-step process.

• Blood in need of oxygen travels to two large veins called the superior and inferior vena cava.
• The superior and inferior vena cava transport blood into the right atrium.
• The right atrium contracts causing the tricuspid valve to open and blood to flow into the right ventricle. Once the right ventricle fills, the tricuspid valve closes to keep blood from flowing backward.
• The right ventricle contracts causing the pulmonary valve to open and blood to flow into the pulmonary artery.
• The pulmonary artery delivers blood to the lungs to be re-oxygenated.
• The pulmonary veins return the oxygen-rich blood to the heart's left atrium.
• The left atrium contracts causing the mitral valve to open and blood to flow into the left ventricle. Once the right ventricle fills, the mitral valve closes to keep blood from flowing backward.
• The left ventricle contracts causing the aortic valve to open and blood to flow into the aorta.
• The aorta carries blood to smaller arteries that deliver the oxygen rich blood throughout your body to your tissues, organs and muscles, including the heart muscle itself. The arteries that carry oxygen rich blood to the heart muscle are called coronary arteries.