Body defences against pathogens

How does the skin protect the body?

It forms a physical barrier that prevents pathogens entering the body.

What is the role of mucus in the respiratory system?

It traps pathogens and particles.

What is the role of cilia in the respiratory system?

They move mucus containing trapped pathogens towards the throat, where it can be swallowed.

What are lysozymes?

Enzymes that break down bacterial cell walls.

Where are lysozymes found?

In secretions such as tears and saliva.

How does hydrochloric acid protect the body?

Stomach acid creates a low pH that kills many pathogens swallowed with food or mucus.

What is the difference between physical and chemical defences?

Physical defences block or remove pathogens, while chemical defences damage or kill them.

Why is mucus useful even though it does not necessarily kill pathogens?

It traps pathogens so they can be removed from the respiratory tract.