# Explain how the structure of arteries, veins and capillaries is related to their functions in the human circulatory system.

> Eduqas A-Level Biology — 2.1 Classification and biodiversity · Explain · 5 marks

## Mark scheme (5 marks)

1. Arteries have thick muscle and elastic layers / thick walls to withstand or maintain high blood pressure (accept: to prevent bursting)
2. Veins have thin muscle and elastic layers / thin walls because blood is at low pressure
3. Veins contain valves to prevent backflow of blood
4. Capillaries have a thin wall / thin diameter to decrease the diffusion distance, allowing exchange of substances between the blood and tissues
5. Capillaries have a large surface area / extensive network so that every cell in the body is close to a capillary (accept: slower blood flow allows time for exchange)

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-arteries-c00e0b5d) · Published by Druglandscape Ltd.