Pathogens
Pathogens is a disease-causing microorganism.
Infection — The entry of pathogen into the body.
Transmissible Disease
Pathogens are passed on from one host to another and therefore the disease they cause are known as transmissible diseases.
- Direct Contact: The pathogens is passed directly from one host to another by transfer of body fluids such as blood or semen. Blood to blood; body fluids to body fluids.
- e.g. Human Immunodeficiency Disease, Gonorrhoea, Hepatitis B & C
- Indirect Contact: The pathogens leaves the host and is carried by an intermediate medium.
- e.g. Contaminated surfaces, air such as droplets or aerosols, food, water, or organisms like insects such as mosquitoes carrying malaria or dengue.
- Droplets in Air — Common Cold, Influenza.
- Food or Water — Cholera, Typhoid, Dysentery.
- Touching Contaminated Surfaces — Athletes Foot, Salmonella.
- Insect Bites — Malaria, Dengue Fever.
Body Defences
Mechanical Barriers
Structures that make it difficult for pathogens to get past them and into the body.
- Skin: Covers almost all parts of your body to prevent infection from pathogens. If it is cut or grazed, it immediately begins to heal itself, often by forming a scab.
- Hairs in the Nose: It makes it difficult for pathogens to get past them further up the nose so they are not inhaled into the lungs through respiratory passages.
Chemical Barriers
Substances produced by body cells that traps or kill the pathogens before they can get further into the body and cause disease.
- Mucus: Made in various places in the body, pathogens get trapped in the mucus and can then be removed from the body by coughing, blowing the nose, swallowing, etc.
- Stomach Acid: Contains hydrochloric acid which is strong enough to kill any pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water.
Cells Defences
Different types of white blood cells work to prevent pathogens reaching areas of the body they can replicate into. (CH9 / Blood.)