Pathogens summary

What is disease? not a single thing, description of certain symptoms, phys, mental or both. Suggests a malfunction of body or/and mind.

What causes disease?Infectious diseases caused by micro-organisms – include bacteria, viruses, parasites and fungi

Micro-organisms that that cause disease are pathogens.

Remember there are many different microorganisms found on and in the human body. Most do no harm.

How do pathogens enter the body?

Pathogen must penetrate one of the organism interface with the environment.

One such interface is skin – Outer layer of skin consists of dead, dry cells made of an indigestible protein, keratin.

Some interfaces of the body have evolved to exchange of material between the internal and external.

Thin, moist, large SA, well supplied with blood vessels. So include;

Gas exchange system – flu, tb, bronchitis

Digestive system – pathogens carried by food and water – Cholera,typhoid and dysentery.

Prevent entry, natural defences. Mucus, enzymes, stomach acid.

How do pathogens cause disease?

1.Damaging host cells – sometimes sheer number cause damage by preventing normal tissue function.

Viruses inhibit synthesis if DNA, RNA and protein synthesis

Many pathogens will break down membranes

2. Producing toxins – most bacterial produce toxins. The cholera bacterium produces a toxin that leads to excessive water loss from the lining of the intestines.