Important parts of circulatory system are heart, capillaries, veins, and arteries. The arteries are responsible for carrying red blood from heart and deliver oxygen to capillaries. Then capillaries deliver the waste carrying blood or deoxygenated blood to veins back to the heart.
But not all arteries carry blood with oxygen, the pulmonary arteries carry deoxygenated blood and not all veins carry blood with carbon dioxide, the pulmonary veins carry blood with oxygen.
