# Explain why the human circulatory system is described as a double circulatory system.

> WJEC GCSE Biology (Wales) — 1.4.1 Blood and circulation · Explain · 4 marks

## Mark scheme (4 marks)

1. Blood passes through the heart twice for each complete circuit of the body
2. One circuit carries blood from the heart to the lungs and back (pulmonary circulation)
3. The other circuit carries blood from the heart to the rest of the body and back (systemic circulation)
4. This ensures oxygenated and deoxygenated blood are kept separate / maintains high pressure to the body

## Key terms

- [double circulatory system](https://www.gradenine.co.uk/glossary/double-circulatory-system)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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-why-the-human-circulatory-system-2120c456) · Published by Druglandscape Ltd.