Vein/veɪn/ Definition 1 of 3Pro Tip 1/3Directional Flow Veins carry blood towards the heart, unlike arteries which carry blood away. During the surgery, the doctor monitored the blood flow in the veins. Pro Tip 2/3Medical Procedures Veins are often used for medical procedures like drawing blood or intravenous therapy. The nurse found a vein in my arm for the IV drip. Pro Tip 3/3Visibility Some veins can be seen under the skin, especially on the hands and arms. You can see the blue veins clearly on his pale wrists.