Defence against Diseases

Microorganisms – Bacteria, Fungi, Viruses. The Microorganisms that cause disease are called pathogens.

People can pass these pathogens on from person to person. This makes them Infectious diseases.

Bacteria – Produces anti-toxins (poisons). Single cell living organisms. Much smaller then plant/animal cells. Many bacteria cells are harmless and some are actually beneficial in life. Bacteria multiply by splitting in two.

Viruses – Gets into the cells and reproduces rapidly. This causes the cell to be permanently damaged. These microorganisms are much smaller then bacteria cells. Viruses cause disease in every single living organism.

Symptoms – high temperatures, headaches, and rashes. This is caused by the damage the pathogens do to your body and also how your body reacts to the toxins they produce.

There are a number of ways in which pathogens can be spread. The most likely ones are:

· Droplet Infection – When you cough, sneeze or talk you expel tiny droplets. Other people breathe these droplets in along with the pathogens they contain, so they pick up the infection.

· Direct Contact – When pathogens get in small breaks/cuts in skin. Injecting with dirty needles, eating raw undercooked food. Spread by direct contact of skin.

Bodies’ defences

Skin – your skin is your bodies’ main defence when it comes to pathogens. It acts as a barrier and covers your whole body.

Clots – When you cut your skin, you blood instantly forms a clot which dries to make a scab. The scab seals of the cut so pathogens can’t get into the wound.

Mucus – When you breathe, you breathe in pathogens. Luckily your body produces mucus. Mucus is a sticky liquid that pathogens get stuck in. It covers the lining of your lungs and tubes. You then swallow the mucus and acid in your stomach destroys the microorganism.

When your outer body defences fail your white blood cells take action.

White blood cells – ingest pathogens, produce antibodies or they can produce antitoxins.

Ingest microorganisms – They ingest the pathogen. This destroys the pathogen so they can’t make you ill

Antibodies – Some white blood cells produce special chemicals called antibodies. There is a different antibody for each pathogen. If the pathogen gets into your body a second time the antibody can be made very quickly

Antitoxins – counter act the toxins that are released by the pathogens.

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Hopefully this will help you out. This is with AQA and it's Biology Unit 1. Message if you need any help.