Human Defence Systems

The Skin

barrier to pathogens, also secrets antimicrobial substances which kill pathogens

The Eyes

tears, which have enzymes

The Nose

hairs & mucus in your nose trap particles that could contain pathogens

The Mouth

saliva (with enzymes) and mucus

Trachea and Bronchi

secrete mucus to trap pathogens. They are also lined with cilia, hair -like structures that waft mucus up to the back of the throat, where it can be swallowed

The Stomach

produces hydrochloric acid, that kills pathogens that make it far from the mouth

When does the immune system kick in?

If pathogens do enter your body, your immune system destroys them

What are the three ways that white blood cells attack?

When they spot an invading microbe, they either consume it, produce antibodies, or release antitoxins that neutralize toxins produced by pathogens.

Explain how WBC consume pathogens?

Phagocytes can engulf foreign cells and digest them through the process of phagocytosis

Explain how WBC produce antibodies to kill pathogens?

B Lymphocytes produce antibodies (and antitoxins) when they come across a foreign antigen (unique molecules on the surface of pathogens).

These complementary antibodies lock onto the antigens, marking them for destruction or neutralisation by other WBC

What happens when someone is infected twice, by the same pathogen?

WBC rapidly produce antibodies to kill it- they’re naturally immune

Explain how anti-toxins help kill pathogens

Antitoxins conteract toxins produced by invading bacteria