Human Defence Systems — Non-Specific

The human body has several lines of defence that work together to prevent pathogens from entering and causing disease. This lesson focuses on the non-specific defences — barriers and mechanisms that protect against all pathogens, regardless of type. This is a key topic in the AQA GCSE Combined Science Trilogy specification (8464).

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Specific vs Non-Specific Defence

Before studying the defences in detail, it is important to understand the difference:

Type	Description	Examples
Non-specific defence	Works against all pathogens equally; does not target a specific pathogen	Skin, mucus, stomach acid, cilia
Specific defence	Targets a particular pathogen using the immune system	White blood cells producing antibodies

Non-specific defences are sometimes called the body's first line of defence because they act before the immune system is activated.

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The Body's Non-Specific Defences

1. The Skin

The skin is the body's largest organ and acts as a continuous physical barrier to prevent pathogens entering: