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The heart is the organ at the centre of the circulatory system, pumping blood around the body to deliver oxygen and nutrients and remove waste products. This lesson covers the structure of the heart, the double circulatory system, and the three types of blood vessel — all as required by the AQA GCSE Combined Science Trilogy specification (8464).
Mammals, including humans, have a double circulatory system. This means that blood passes through the heart twice during each complete circuit of the body.
graph LR
subgraph "Circuit 1 — Pulmonary"
H1["Right side of heart"] -->|"Deoxygenated blood"| L["Lungs"]
L -->|"Oxygenated blood"| H2["Left side of heart"]
end
subgraph "Circuit 2 — Systemic"
H2 -->|"Oxygenated blood"| B["Body tissues"]
B -->|"Deoxygenated blood"| H1
end
| Circuit | Name | Blood Flow | Purpose |
|---|---|---|---|
| Circuit 1 | Pulmonary circulation | Heart → lungs → heart | Blood picks up oxygen and releases carbon dioxide |
| Circuit 2 | Systemic circulation | Heart → body → heart | Blood delivers oxygen and nutrients to cells and removes waste |
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