Arteries carry blood from your heart to the rest of your tissues. Veins return blood from the rest of your body to your heart, so the blood can be recirculated. To return blood to your heart, the veins in your legs must work against gravity. Muscle contractions in your lower legs act as pumps, while toned, elastic vein walls help blood return to your heart. Tiny one-way valves in your veins open as blood flows toward your heart then close to stop blood from flowing backward.
As you get older your veins can lose elasticity, causing them to stretch. The valves in your veins may become weak, allowing blood that should be moving toward your heart to flow backward. Blood pools in your veins, and your veins enlarge and become varicose. The veins appear blue because they contain deoxygenated blood, which is in the process of being recirculated.
Some pregnant women develop varicose veins. Pregnancy increases the volume of blood in your body, but decreases the flow of blood from your legs to your pelvis. This circulatory change is designed to support the growing fetus, but it can produce an unfortunate side effect — enlarged veins in your legs. Varicose veins may surface for the first time or may worsen during late pregnancy, when your uterus exerts greater pressure on the veins in your legs. Hemorrhoids are varicose veins located in and around the anus.