Microbes and disease

The infectious diseases are caused by pathogens.

NOT all microbes are pathogens.
But all pathogens are microbes.

A pathogen is a microbe that causes disease:

-- bacteria - bronchitous, typhoid, tuberculosis
-- viruses - warts, herpes, flu, measles, smallpox
-- fungi - athletes foot, ring worm

Once a pathogen has entered the body it has food (body) warmth and moisture. They can reproduce very quickly. Bacteria doubles every 20 mins, 1 bacteria - 20 minutes - 32,763 bacteria.

Infection - when the pathogen enters the body
Disease - when there are observable symptoms

How can we stop pathogens from entering the body?

Disinfectant - used to kill pathogens on non-living surfaces
antiseptic - used to kill pathogens on living surfaces

Bodys External Defences

Mouth - amylase in saliva breaks down pathogens - disease T.B
Nose - hairs + mucas that trap down pathogens - disease influenza
Ears - hairs + mucas/ ear wax - Ear infection
Cuts + grazes - blood will clot and wounds will scab - tetanus
Eyes - Enzymes in your tears - conjunctivitis
Genital area - no protection - Chlamydia

There are two types of white blood cell which destroy pathogens in different ways.

phagocytes - engulf pathogens and break them down
Lymphocytes - produce antibodies in response to specific pathogens, antibodies destory pathogens in three ways
--They make the pathogens burst
--They stick antigens on the surface of the pathogen and allows the phagocytes to- recognise and engulf them.
--Cause the pathogens to stick together in one big clump

Most pathogens also produce toxins. It is often the toxin that causes the symptoms and not the pathogen. Both phagocytes and Lymphocytes produce anti-toxins to destroy the toxins.

antibiotics - kill bacteria ONLY!

The antibodies made by lymphocytes will destroy 1 type of pathogen only. The lymphocytes can remember how to make the antibody, should the same pathogen enter the body through a second time. If you have a healthy immune system you do not get some infectious disease twice and this is called your natural immunity.

If you ar einjected with a dead or weakened pathogen then your lymphocytes will make the specific antibody, but you should not get ill. If the pathogen enters for the second time you can quickly make antibodies and will not become ill, this is called your artificial immunity - vaccination, immunisation, jab.