# Double circulation

Blood passes through the heart twice on each full trip: once to the lungs and once to the body.

Biology (school) · Part 03: The human body · Card 5 of 11 · Last updated 2026-10-19

## Analogy

A figure of eight, with the heart at the crossing.

## In practice

The right side pumps blood to the lungs. The left side pumps it round the body.

## Practice

### Flashcards

- **Which side of the heart pumps blood to the lungs?** The right side.

## Questions people ask

### Why does the left side of the heart have a thicker wall?

The left ventricle must pump blood all the way around the body at high pressure, while the right ventricle only pumps blood a short distance to the lungs. A thicker muscle wall on the left produces a stronger push to reach the head, arms and legs.

### What are arteries, veins and capillaries?

Arteries carry blood away from the heart and have thick, elastic walls to cope with high pressure. Veins carry blood back to the heart and have valves to stop backflow. Capillaries are tiny vessels with walls one cell thick, where substances pass between blood and body cells.

## Related concepts

- [Blood](https://studyvisually.com/learn/science/biology-school/biology-school-part-3/biology-school-part-3-concept-6)
- [Coronary heart disease](https://studyvisually.com/learn/science/biology-school/biology-school-part-3/biology-school-part-3-concept-7)

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