# Explain why the human circulatory system is described as a double circulatory system and explain the advantage this gives over a single circulatory system.

> Pearson Edexcel A-Level Biology A (9BI0) — 1.3 Mass transport in animals · Explain · 5 marks

## Mark scheme (5 marks)

1. Blood passes through the heart twice per 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. The heart re-pressurises the blood after it returns from the lungs, so blood is delivered to the body at high pressure
5. This means oxygen / nutrients are delivered to body tissues more quickly / efficiently than in a single circulatory system

## Key terms

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

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-human-circulatory-system-78bd659f) · Published by Druglandscape Ltd.