# Describe the roles of the intercostal muscles and diaphragm during inhalation in humans.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.9 Gas exchange: humans · Describe · 4 marks

## Mark scheme (4 marks)

1. The intercostal muscles contract during inhalation
2. Contraction of the intercostal muscles moves the ribcage upwards and outwards
3. The diaphragm contracts and flattens (moves downwards)
4. These movements increase the volume of the thorax / chest cavity, which decreases the air pressure inside the lungs, so air moves in

## Key terms

- [intercostal muscles](https://www.gradenine.co.uk/glossary/intercostal-muscles)
- [diaphragm](https://www.gradenine.co.uk/glossary/diaphragm)
- [inhalation](https://www.gradenine.co.uk/glossary/inhalation)

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-roles-of-the-intercostal-37774ec7) · Published by Druglandscape Ltd.