Human Defences Against Micro-Organism

Key Stage 4

Meaning

Human defences against micro-organisms are all the ways the human body can prevent infection by a pathogen.

About Human Defences against Micro-organisms

Defences against micro-organisms can be broken down into two main groups: Chemical Defences and Physical Barriers.

The Skin

The human body is covered in skin which acts as a physical barrier to prevent micro-organisms from getting into the blood or organs.

The skin has sweat glands which produce sweat which contains antimicrobial chemicals which can kill pathogens.

When the skin is cut the blood can clot to produce another physical barrier to stop pathogens getting into the body.

The Nose

The nose has hairs which act as a physical barrier as they can trap microorganisms before they enter the lungs.

The nose is full of mucus which acts as a physical barrier since it is a sticky substance which microorganisms can get stuck in. This mucus is then swallowed into the harsh environment of the stomach which kills microorganisms.

The Trachea

The trachea is full of mucus which acts as a physical barrier since it is a sticky substance which microorganisms can get stuck in. This mucus is then swept up away from the lungs by Ciliated Epithelial Cells into the throat where it is then swallowed into the harsh environment of the stomach which kills microorganisms.

The Eyes

The eyelids sweep micro-organisms from the surface of the eyes.

The eyelashes prevent some micro-organisms getting into the eyes.

The tear ducts produce Lysosomes which are antimicrobial chemicals.

The Stomach

The stomach is kept at a very low pH with Hydrochloric Acid which kills most micro-organism which enter the stomach.