Which blood vessels carry blood toward the heart?
General information only. This article explains the basics and is not medical advice. For anything about your own health, talk to a doctor or other qualified professional.
Quick answer
Veins are the blood vessels that carry blood toward the heart. Most carry oxygen-poor blood back from the body’s tissues. Arteries do the opposite, carrying blood away from the heart, and tiny capillaries connect the two. Many veins contain one-way valves that stop blood from flowing backward.
Three types of blood vessels
| Vessel | Direction | Walls | Pressure |
|---|---|---|---|
| Arteries | Away from the heart | Thick, muscular, elastic | High |
| Capillaries | Connect arteries and veins | One cell thick | Low |
| Veins | Toward the heart | Thinner, less muscular | Low |
The body’s main artery is the aorta; see the main artery in the body. The largest veins are the superior and inferior venae cavae, which empty into the heart’s right atrium.
The exception
The rule is about direction, not oxygen. The pulmonary veins carry oxygen-rich blood from the lungs to the heart, while the pulmonary arteries carry oxygen-poor blood to the lungs. See how many chambers the heart has.
How blood climbs back up
Blood in your legs has to travel upward against gravity at low pressure. Veins manage it with:
- One-way valves that close if blood starts to slip backward
- The muscle pump: when leg muscles contract while you walk, they squeeze veins and push blood up
- Breathing, which changes pressure in the chest and helps draw blood upward
Weak valves can let blood pool, causing swollen, twisted varicose veins.
Why do veins look blue?
Blood is always red, darker when it carries less oxygen. Veins look blue because of how light travels through skin: red light penetrates deeper and is absorbed, while blue light is reflected back toward our eyes.
Blood vessel facts
- Laid end to end, an adult’s blood vessels would stretch roughly 100,000 km, about two and a half times around Earth (most of that length is capillaries).
- At any moment, about 60–70% of your blood is in your veins.
- Blood samples are usually taken from veins because they’re close to the surface and have lower pressure.
For what blood is made of, see what white blood cells do and which blood type is the universal donor.
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