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The human body has a range of non-specific defences that act as the first line of defence against pathogens. These defences work against all pathogens — they do not target specific ones. In this lesson you will learn about the physical and chemical barriers that prevent pathogens from entering the body.
The body's defences can be thought of in layers:
| Line of defence | Type | How it works |
|---|---|---|
| First line | Non-specific (physical and chemical barriers) | Prevents pathogens from entering the body |
| Second line | Non-specific (immune cells) | Phagocytes engulf and destroy pathogens that get past the first line |
| Third line | Specific (immune response) | Lymphocytes produce antibodies and antitoxins targeted at specific pathogens |
This lesson focuses on the first line of defence — the physical and chemical barriers.
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