The heart is the main organ involved in blood circulation. Arteries carry oxygenated blood away from the heart to the body while the veins carry deoxygenated blood from different parts of the body to the heart for purification. Pulmonary artery and pulmonary veins are an exception. The pulmonary artery carries deoxygenated blood away from the heart, while the pulmonary vein carries oxygenated blood to the heart. The oxygenated blood is carried by the pulmonary veins from the lungs to the left auricle. This is called auricular circulation.