# Explain how the structure of arteries and veins makes each vessel suited to its function in the circulatory system.

> Pearson Edexcel A-Level Biology A (9BI0) — Topic 4 Exchange and Transport · Explain · 5 marks

> Arteries carry blood away from the heart under high pressure, while veins return blood to the heart under low pressure.

## Mark scheme (5 marks)

1. Arteries have thick walls containing thick layers of smooth muscle and elastic fibres
2. This allows artery walls to withstand / stretch and recoil with the high pressure of blood pumped from the heart
3. Veins have thinner walls than arteries / relatively thin walls
4. Veins have a wider lumen than arteries (of comparable size)
5. Veins contain valves to prevent the backflow of blood and ensure blood moves towards the heart under low pressure

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-arteries-f29ed063) · Published by Druglandscape Ltd.