# Describe how the body's natural defences prevent pathogens from entering the bloodstream.

> AQA GCSE Biology (8461) — 4.3.1 Communicable diseases · Describe · 4 marks

## Mark scheme (4 marks)

1. Skin acts as a physical barrier / prevents pathogens entering the body
2. Mucus in the nose / trachea / airways traps pathogens / microorganisms
3. Cilia move mucus (and trapped pathogens) away from the lungs / towards the throat
4. Stomach acid / hydrochloric acid kills pathogens that are swallowed

## Key terms

- [pathogen](https://www.gradenine.co.uk/glossary/pathogen)

## Related

- [Revision notes for AQA GCSE Biology (8461)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-the-body-s-natural-defences-0f8d848a) · Published by Druglandscape Ltd.