How does the circulatory system help your cells get rid of carbon dioxide?

The blood flowing through the veins carry the carbon dioxide from the cells of all parts of the body to the heart. Hence we say that the veins transmit the De-oxygenated blood from all parts of the body to the heart. The De-oxygenated blood collected in the heart flows to the lungs through the pulmonary artery. The blood gets oxygenated in the lungs. Then the oxygenated blood flows to the heart through the pulmonary vein. Then the oxygenated blood flows to all parts of the body through the arteries. So blood flows into the heart through the veins, and flows out of the heart through the arteries. Normally the De-oxygenated blood flows through the veins and the oxygenated blood flows through the artery. The only exceptions are the pulmonary artery that transmits de-oxygenated blood from heart to the lungs and the pulmonary vein that transmits oxygenated blood from lungs to heart. This is because blood flows into the heart by veins and flows out of the heart by arteries.