To understand the question lets go to the basics of the vasculature. Arteries are the blood vessels that bring blood away from the heart, while veins bring blood back to the heart. Normally arteries carry oxygen rich blood throughout the body, and vein carry oxygen poor blood. The only two exceptions of this rule are the pulmonary vasculature (Pulmonary Veins bring oxygenated blood from the lungs to the heart) and the umbilical vasculature (fetuses).