# A patient has a blocked coronary artery. Explain why a blockage in a coronary artery is dangerous and describe how the heart's double circulatory system normally ensures that the body tissues receive enough oxygen.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 1.2 Heart, blood and blood vessels · Explain · 5 marks

> Coronary heart disease occurs when fatty deposits build up inside the coronary arteries, reducing blood flow to the heart muscle. It is one of the leading causes of death in the UK.

## Mark scheme (5 marks)

1. Coronary arteries supply the heart muscle (myocardium) with oxygenated blood / oxygen and glucose
2. A blockage means the heart muscle cannot respire aerobically / cannot receive enough oxygen, so it stops beating properly / heart attack occurs
3. The double circulatory system has two circuits: the pulmonary circuit (heart to lungs and back) and the systemic circuit (heart to body and back)
4. Blood is oxygenated in the lungs and returned to the heart before being pumped at high pressure to the body tissues
5. This ensures body tissues / cells receive a good / constant supply of oxygenated blood for aerobic respiration

## Key terms

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

## 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/a-patient-has-a-blocked-coronary-4be7f8e0) · Published by Druglandscape Ltd.