# Describe how the structure of the human circulatory system is adapted to supply all body cells with the substances they need.

> AQA A-Level Biology (7402) — 3.3.4 Mass Transport · Describe · 5 marks

> The human circulatory system transports substances around the body. It consists of the heart, blood vessels and blood.

## Mark scheme (5 marks)

1. The heart pumps blood / acts as a pump to move blood around the body
2. It is a double circulatory system / blood passes through the heart twice per complete circuit
3. Arteries carry oxygenated blood away from the heart (to organs/tissues) at high pressure
4. Capillaries have thin walls / are one cell thick, allowing exchange of substances with body cells
5. Blood transports oxygen / glucose / nutrients to cells and removes carbon dioxide / waste products

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