# Explain why the mammalian heart is described as a 'double pump', and explain how this arrangement is advantageous for delivering oxygen to respiring tissues.

> OCR A-Level Biology A (H420) — 3.2 Transport in animals · Explain · 4 marks

> The mammalian circulatory system consists of two circuits: the pulmonary circuit, which carries deoxygenated blood to the lungs, and the systemic circuit, which carries oxygenated blood to the rest of the body. Both circuits are driven by a single organ — the heart.

## Mark scheme (4 marks)

1. The right side of the heart pumps blood to the lungs (pulmonary circuit) and the left side pumps blood to the body (systemic circuit), so the two sides function as separate pumps.
2. Blood passes through the heart twice in one complete circuit of the body (double circulation).
3. Separating the two circuits prevents mixing of oxygenated and deoxygenated blood, maintaining a high oxygen concentration / high partial pressure of oxygen delivered to tissues.
4. The left ventricle generates higher pressure than the right, allowing oxygenated blood to be delivered rapidly / at high pressure to distant systemic tissues, sustaining a high rate of oxygen delivery to meet metabolic demand.

## Key terms

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

## Related

- [Revision notes for OCR A-Level Biology A (H420)](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-mammalian-heart-is-98722779) · Published by Druglandscape Ltd.