10. Diseases and Immunity
Pathogen
A disease causing organism
Transmissible disease
A disease in which the pathogen can be passed from one host to another
How a pathogen is transmitted
(a) by direct contact - including through blood and other body fluids
(b) indirectly - including from contaminated surfaces, food, animals and air
Body Defences
● Physical barriers:
1. Hair in the nose: It traps dust particles from getting inside the lungs.
2. Skin: When the skin is cut, it immediately heals itself forming a scab.
● Chemical barriers:
1. Stomach acid: Strong acid that kills any harmful microorganism if consumed.
2. Mucus: Sticky substance produced by goblet cells which beats away dust particles
and other potentially harmful microorganisms.
● White blood cells:
1. Lymphocytes produce antibodies and destroy the pathogens.
2. Phagocytes engulf pathogens.
Controlling the spread of diseases through:
(a) a clean water supply
(b) hygienic food preparation
(c) good personal hygiene
(d) waste disposal
(e) sewage treatment
Pathogen
A disease causing organism
Transmissible disease
A disease in which the pathogen can be passed from one host to another
How a pathogen is transmitted
(a) by direct contact - including through blood and other body fluids
(b) indirectly - including from contaminated surfaces, food, animals and air
Body Defences
● Physical barriers:
1. Hair in the nose: It traps dust particles from getting inside the lungs.
2. Skin: When the skin is cut, it immediately heals itself forming a scab.
● Chemical barriers:
1. Stomach acid: Strong acid that kills any harmful microorganism if consumed.
2. Mucus: Sticky substance produced by goblet cells which beats away dust particles
and other potentially harmful microorganisms.
● White blood cells:
1. Lymphocytes produce antibodies and destroy the pathogens.
2. Phagocytes engulf pathogens.
Controlling the spread of diseases through:
(a) a clean water supply
(b) hygienic food preparation
(c) good personal hygiene
(d) waste disposal
(e) sewage treatment
