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8C Microbes and disease
© Tony P. Thould
September 2000
DISEASES CAN MAKE
YOU UNHEALTHY
Diseases are caused by Microorganisms.
Examples of Micro-organisms are
Bacteria, Viruses, Fungi and
Protozoa
MICRO-ORGANISMS AND
DISEASE
Whooping
Cough
BACTERIA
VIRUSES
Tuberculosis
DISEASES
CAUSED BY
Typhoid
Chicken
Pox
Common
Cold
Measles
OTHERS
Ringworm
Malaria
DISEASE CAN UPSET
THE BALANCE
Many diseases upset the balance of
the body by causing fever, sweating
and other such symptoms.
Therefore the body has to stop
micro-organisms getting into the
body or fight the disease.
MICROBIAL BARRIERS
If they cannot get into your body or
are destroyed as soon as they do,
then you cannot get the disease!
How is the body adapted to stop
Microbes getting into the body or
destroy them once they get in?
How do these barriers help to stop the body from
getting disease?
•SKIN covering the body
•CILIATED EPITHELIAL CELLS lining the
windpipe
• DILUTE HYDROCHLORIC ACID made by
the lining of the stomach
•HAIRS lining the nose
•MUCUS lining the windpipe and nose
•MICROBES living in the body normally
BARRIERS
•SKIN forms a barrier unless cut / damaged
•CILIATED epithelial cells in the trachea trap
and sweep dust out of the windpipe into the
stomach
•ACID in the stomach act as a disinfectant
•HAIRS in the nose filters the air
•MUCUS membranes lining the lungs traps dust
•MICROBES living in the gut destroy other
Microbes.
WHITE CELL
Defends body against disease by killing
Microbes - Bacteria and Viruses
White Cell
Bacterium
Defends body against disease by killing
Microbes - Bacteria and Viruses
They do this by engulfing them - surrounding the
bacteria and trapping it inside the cell and
destroying it.
They also make chemicals called Antibodies which kill
the bacteria a few days after being infected.
White Cells Defend the Body
The white cells identifies a
disease causing microbe
The white cells makes the
right antibody to kill it
White Cells Defend the Body
The antibody stays in the blood
so that if the microbe returns it
will be killed instantly and the
person will not get the disease.
They are IMMUNE
IMMUNITY
The Antibodies made by the white cells
gives us a Natural Immunity to the
disease.
By having an injection with a Vaccine our
body has an Artificial Immunity to the
disease
IMMUNITY GIVES US RESISTANCE TO
CERTAIN DISEASES
ARTIIFICIAL IMMUNITY
A weak or altered form of the disease is injected
into the blood or put on a sugar lump and
swallowed.
The white cells think that there is a full scale
invasion of the disease and produces antibodies to
kill the disease causing organisms.
The antibodies stay in the blood for a long time so
if the disease causing organisms return they are
killed off at once. You are Immune to the disease.
VACCINATIONS
Vaccines may either be injected into the
blood stream or taken by mouth. Some
need to be given a booster dose later in
order to keep up the resistance to the
disease.
Which diseases have you been
vaccinated against, when, how?
How do you get diseases if you
have all of these barriers?
•Through cuts and abrasions in the skin.
•On food swallowed entering the digestive
system due to badly prepared or uncooked
food.
•Droplet infection, where someone sneezes or
coughs and you breathe the tiny moist
droplets in through your nose into your
lungs.
THE PLACENTA
The Umbilical Cord
carries food and
Oxygen to the baby
and waste away
Food and
Oxygen in
the mothers
blood
Placenta
Waste food and
Carbon Dioxide
THE PLACENTA
The Placenta forms a barrier between the
blood of the mother and the baby but allows
substances to pass between them.
Placenta
THE PLACENTA
Unfortunately, some harmful substances can
pass from the mothers blood into the baby
e.g. Alcohol, Drugs, Nicotine and AIDS
Placenta
ANTIBIOTICS
If you have a sore throat due to a bacterial
infection, the doctor may give you some
Antibiotics - usually Penicillin. This usually
kills many different sorts of bacteria and
aids recovery.
Antibiotics are no good at fighting Viruses,
they just do not work on them.