Human Defences: Chemical Barriers Flashcards

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What is a chemical barrier in human defence?

A body substance that kills or stops microbes before they cause disease.

How does stomach acid protect you from infection?

It is very acidic (about pH 2) and kills many microbes in food and drink.

What is lysozyme?

An enzyme that breaks down bacterial cell walls.

Name two body fluids that contain lysozyme.

Tears and saliva, and also mucus in the airways.

How do tears protect your eyes from infection?

Tears contain lysozyme, which kills bacteria on the eye surface.

How do sweat and sebum on the skin help stop infection?

They make skin slightly acidic and contain chemicals that slow or kill microbes.

What happens to microbes trapped in airway mucus after you swallow it?

Stomach acid destroys them.

What does antimicrobial mean?

Kills microbes or stops them growing.

Are chemical barriers specific to one pathogen?

No. They are non-specific and act against many microbes.

Give three examples of human chemical barriers.

Stomach acid, lysozyme in tears or saliva, and chemicals in sweat and sebum.