Describe how the structure of the human circulatory system is adapted to supply all body cells with the substances they need.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The human circulatory system transports substances around the body. It consists of the heart, blood vessels and blood.
Model answer (5 marks)
The heart acts as a pump, moving blood around the body.
The system is double‑circulatory, so blood passes through the heart twice in one circuit.
Arteries carry oxygenated blood away from the heart to organs and tissues under high pressure.
Capillaries have one‑cell‑thick walls, allowing exchange of substances with body cells.
Blood transports oxygen, glucose and other nutrients to cells and removes carbon dioxide and waste products.
The system is double‑circulatory, so blood passes through the heart twice in one circuit.
Arteries carry oxygenated blood away from the heart to organs and tissues under high pressure.
Capillaries have one‑cell‑thick walls, allowing exchange of substances with body cells.
Blood transports oxygen, glucose and other nutrients to cells and removes carbon dioxide and waste products.
Examiner tips
- Use the exact terms: pump, double circulatory, arteries, capillaries, transport oxygen, glucose, remove CO₂.
- Show the flow: heart → arteries → capillaries → veins → heart.
- Keep each point concise and separate with line breaks or numbers.
Common mistakes
- Confusing arteries with veins (mixing oxygenated/ deoxygenated blood).
- Failing to mention the double‑circulatory nature of the system.
Mark scheme (5 marks)
- The heart pumps blood / acts as a pump to move blood around the body
- It is a double circulatory system / blood passes through the heart twice per complete circuit
- Arteries carry oxygenated blood away from the heart (to organs/tissues) at high pressure
- Capillaries have thin walls / are one cell thick, allowing exchange of substances with body cells
- Blood transports oxygen / glucose / nutrients to cells and removes carbon dioxide / waste products
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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