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Akash G 12M

1.0 - Disease
1.1 Pathogens:
Pathogens are disease causing microorganisms
Disease is the symptoms displayed on a person following an infection, a malfunction of the body or mind
Infectious Disease: Caused by bacterium, virus, fungum transferred from one person to another
Non Infectious Disease: A disease that is not caused by a transmitted pathogen (e.g. Stroke, arthritis, obesity)
Interface: A surface or boundary between two systems
For a microorganism to be a pathogen, it must:
 Gain entry to a host
 Colonise tissue of a host
 Resist defences of a host
 Cause damage to the host’s tissue
Methods of transmission:
 Airborne
 Waterborne
 Direct Contact
 Contaminated food
 Animals (vectors)
Common Interfaces of the body:
 Gas Exchange System: through the mouth and nose (TB, influenza, bronchitis)
 Digestive System: through food and water (cholera, typhoid, dysentery)
 Skin: Through open cuts and wounds straight into the bloodstream (HIV, AIDS)
The body’s natural defence includes:
 The skin o Body has a natural flora of bacteria keeping the pH levels low, o Sweat and oil is antiseptic o Blood clots by soluble blood protein fibrinogen is converted into an insoluble fibrous protein – fibrin, which creates a mesh for platelets to stick onto o White blood cells are attracted to open areas, to prevent infection
 Gas Exchange System: o Mucus lines the passageways trapping invading pathogens o These are moved to the top of the system by wafting cilia, to be removed o Macrophages remove any pathogens that get beyond the mucus
 Digestive System: o Mucus is antiseptic to kill bacteria o Gastric juice contains HCL which has a low pH to kill bacteria, by denaturing the pathogen’s enzymes and protease which digests the bacterial cell wall which is made up of protein. o Friendly bacteria in the stomach help to remove harmful bacteria
 Enzymes such as lysosomes are present in the tears and saliva to destroy any