# Veins contain valves, whereas arteries do not. Explain why veins need valves to function correctly and why arteries do not require them.

> Cambridge International IGCSE Biology (0610) — 9.3 Blood vessels · Explain · 4 marks

## Mark scheme (4 marks)

1. Blood in veins travels at low pressure, so valves are needed to prevent backflow of blood towards the tissues.
2. Valves in veins ensure blood flows in one direction, towards the heart.
3. Blood in arteries is under high pressure, so backflow does not occur.
4. The thick elastic and muscle walls of arteries maintain this high pressure, so valves are not needed.

## Key terms

- [vein](https://www.gradenine.co.uk/glossary/vein)
- [valve](https://www.gradenine.co.uk/glossary/valve)

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Source: [GradeNine](https://www.gradenine.co.uk/q/veins-contain-valves-whereas-arteries-do-d720906b) · Published by Druglandscape Ltd.