This document has full explanation for Immunity and Disease topic to enable you to solve your past papers perfectly. It is color coded for easy memorization and includes the tips and tricks of previous exams
BIO
LOGY
Dr Ahmed Nasser
Extended curriculum
O-level
, Immunity and Disease
Pathogen
A pathogen is a microorganism (tiny in size so can only be seen by
microscope) that causes a disease by living on body of a host and
ER
breeding there. (A disease causing organism)
SS
NA
D
ME
Mechanism of causing disease
AH
Some pathogens produce poisonous waste products called toxins which
cause damage to host cells.
DR
Other pathogens invade host cells and live inside them using up their
resources and reproduce producing large colonies.
The immune response generated from the host body gives rise to the
following symptoms: raised temperature, headache, tiredness and
weakness, and sometimes diarrhea and vomiting
,Diseases
Infectious NON
Transmissible Infectious
Diseases transmitted from Diseases not transmitted from
individual to another individual to another
Indirect
ER
Degenerative disease:
Check next page bronchitis and COPD
Vitamin deficiency: scurvy or
Direct
rickets
SS
Cancer: genetic predisposition
The passing of a pathogen to an
and risk factors such as UV ray
uninfected person is called
exposure
NA
transmission.
Congenital disease: down
The entry of the pathogen into
syndrome and heart defects
the body is known as infection.
The person (or animal) in which
the pathogen lives and breeds is
D
said to be a host for that
pathogen.
ME
By TOUCH: Athlete's foot
By BLOOD or PLACENTA: HIV
(AIDS)
AH
By SEXUAL INTERCOURSE: HIV,
Gonorrhea, Syphilis, Hepatitis B
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, Indirect
transmission
Respiratory passages (AIR): Droplets in air if you someone ill coughs
or sneezes
eg: (influenza, TB, common cold)
ER
In contaminated food: Salmonella can enter your alimentary canal
with the food you eat
SS
NA
In contaminated water: The bacterium causing cholera & typhoid
and the virus causing poliomyelitis are transmitted in water; if you
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swim in contaminated water or drink it you are at risk of catching the
disease
ME
By vector: protozoan parasite (Plasmodium) is transmitted from
AH
person to person by the bites of infected mosquitoes of the genus
Anopheles (vector) causing malaria. Dogs and racoons are vectors
for rabies virus.
DR
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