Veins

circulatory system · blood vessels · body systems

Highways for blood. Veins are tubes inside your body that carry blood back to your heart. Think of them like return roads in a city, while arteries are the roads going out.

Tired blood returns. Most veins carry deoxygenated blood, which means the blood has already given its oxygen to your cells and needs to go back to the heart and lungs to pick up fresh oxygen.

Special lung veins. Your pulmonary veins are the exception to the rule. These special veins actually carry oxygenated, oxygen-rich blood from your lungs back to your heart so it can pump it out to your whole body.

Thinner and wider. Veins have thinner walls than arteries because the blood pressure inside them is lower and gentler. They're also wider to hold more blood as it slowly returns to your heart.

Deep and surface veins. Your body has two types of veins: deep veins hidden inside near your bones and organs, and surface veins you can sometimes see under your skin on your arms and legs.