Your heart, together with blood vessels and blood, makes up your cardiovascular system. This sophisticated network carries important substances such as oxygen and nutrients to every cell of your body. It also helps transport and eliminate waste products. Your heart works as a pump that pushes blood to the organs, tissues, and cells. Blood delivers oxygen and nutrients and removes the carbon dioxide and waste products made by the cells.

The blood vessels of the cardiovascular system are divided into two main pathways: the blood vessels in the pulmonary circuit carry blood from the heart to the lungs and back to the heart, whether the systemic circuit consists of the pathways between the heart and all other areas of the body.

In the systemic circuit arteries carry oxygen-rich blood away from your heart, and veins carry oxygen-poor blood back to your heart. This process of blood flow within your body is called circulation.

In the pulmonary circulation, though, the roles are switched. The pulmonary artery brings oxygen-poor blood into your lungs and the pulmonary vein brings oxygen-rich blood back to your heart.