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

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 8 Grey Matter · Explain · 5 marks

> The circulatory system transports substances around the body using three types of blood vessel: arteries, capillaries and veins.

## Mark scheme (5 marks)

1. Arteries carry blood away from the heart under high pressure
2. Arteries have thick walls containing smooth muscle and elastic fibres to withstand / maintain high pressure
3. Capillaries are the site of exchange of substances between the blood and the tissues
4. Capillaries have thin walls (one cell thick) to reduce diffusion distance, allowing rapid exchange
5. Veins carry blood back to the heart at low pressure and contain valves to prevent backflow of blood

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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-4e8846c9) · Published by Druglandscape Ltd.