Disease Prevention - Human Disease Prevention Systems (GCSE Biology)

Human Disease Prevention Systems

In this section, we will learn about the defences which aim to stop pathogens entering the body in the first place.

Specific and Non-Specific

When it comes to the immune system, the terms specific and nonspecific are often used a lot, so it’s important to understand exactly what they mean. If a pathogen enters the body, we want to protect against it, but this protection can be specific or non-specific.

Non-Specific Defence

If there is a non-specific defence, it means that the defence fights against pathogens in general – it doesn’t really matter what type of pathogen or which disease it causes.

Specific Defence

If there is a specific defence, it means that the defence is specific against specific pathogens. For example, antibodies are produced against pathogens, as you will learn below, and each antibody is specific to a particular pathogen. So the antibodies against the HIV virus is different to the antibodies against tuberculosis.

Primary Defence Systems

Primary defence systems are the first line of defence. They are also known as non-specific defences, and aim to stop entry of pathogens into the body. They can be physical or chemical.

These defences aren’t specific against specific pathogens (i.e. like how specific antibodies target specific antibodies), but instead the defences protect against pathogens as a whole.

There are several types of primary defences that you need to know about:

• Skin – the skin forms the primary physical defence, by forming a physical barrier stopping pathogens entering the blood. The skin is made up of dead cells, and a substance called keratin strengthens this barrier. The skin also has a chemical defence, as there can be secretion of an antimicrobial fluid (called sebum) onto the surface of the skin to kill pathogens.

Human Disease Prevention Systems

• Nose, trachea, bronchi – exposed parts of the body are at risk of pathogen invasion. These areas include the oral passages, nasal passages, eyes and ears. Goblet cells in these passages secrete mucous, which traps pathogens and dust, and then ciliated cells sweep them back out. Mucous is found in the passages of the nose, trachea and bronchi. Nose hairs also play a role in capturing microorganisms.

• Tears – tears from eyes form a chemical barrier as they contain lysozyme that helps destroy any microorganisms that enter through the surface of the eye.
• Stomach – the stomach secretes gastric acid, which kills pathogens in the food that you have eaten. The protease enzymes (pepsin) in the stomach are adapted to work in the acidic conditions of the stomach due to the presence of hydrochloric acid, so enzyme function isn’t affected.