Artery vs Vein: Differences Explained in 3D
Arteries carry blood away from the heart. Veins carry it back. That one difference explains almost everything else: arteries have thick, stretchy walls to cope with high pressure, while veins have thinner walls and tiny valves to stop blood flowing backwards.
Artery vs vein at a glance
| Artery | Vein | |
|---|---|---|
| Direction | Away from the heart | Towards the heart |
| Blood | Mostly rich in oxygen | Mostly low in oxygen |
| The exception | Pulmonary artery carries low-oxygen blood to the lungs | Pulmonary veins carry oxygen-rich blood from the lungs |
| Pressure | High | Low |
| Walls | Thick, with lots of muscle and stretchy fibres | Thinner, with less muscle |
| Inside space | Narrow | Wider |
| Valves | None, apart from at the heart | Many, to stop blood flowing back |
| Pulse | Yes, you can feel it | No |
| Biggest one | The aorta, about 2.5 cm across | The vena cava, about 2 to 3 cm across |
Why the walls are different
Every heartbeat pushes a surge of blood into the arteries at high pressure. Their thick, muscly, stretchy walls swell with each beat and spring back, which is the pulse you feel in your wrist. By the time blood has squeezed through the capillaries and reaches the veins, most of that pressure is gone. So veins can have thinner walls, but they need help to push blood back uphill to the heart.
How veins push blood back
Veins have small one-way valves along their length. When you walk, the muscles in your legs squeeze the veins and push blood upwards, and the valves shut behind it so it cannot fall back. Breathing helps too, by changing the pressure in the chest.
Quick facts
- Blood is never blue. Veins look blue because of the way light passes through skin.
- Capillaries link the smallest arteries to the smallest veins. Their walls are just one cell thick.
- If all the blood vessels in an adult were laid end to end, they would stretch roughly 100,000 km.
- Doctors take blood from veins because they sit near the surface and have low pressure.
- The aorta is about as wide as a garden hose.
See it in 3D
Artery vs vein questions
What is the main difference between an artery and a vein?
Arteries carry blood away from the heart and veins carry it back to the heart. Arteries have thicker walls and higher pressure, while veins have thinner walls and valves.
Do all arteries carry oxygen-rich blood?
Nearly all do. The exception is the pulmonary artery, which carries low-oxygen blood from the heart to the lungs. The pulmonary veins then bring oxygen-rich blood back.
Why do veins look blue if blood is red?
Blood in veins is dark red. Veins look blue because skin and fat let blue light bounce back more than red light, which travels deeper and is absorbed.
Why can you feel a pulse in an artery but not a vein?
Each heartbeat pushes a wave of high pressure through the arteries, which makes their walls bulge. By the time blood reaches the veins, that pressure has faded.
Do arteries have valves?
Arteries have no valves along their length. The only valves are at the start of the two big arteries leaving the heart. Veins have many valves to stop blood flowing backwards.
More face-offs: see all 3D comparisons.
The 3D Human Anatomy simulator is made by Julian Neagu, a solo founder in London, as part of VisionVix Simulators. It is free to use in the browser on desktop and phone, with no sign-up.