Transcript Defense Against Disease

Friday, April 1, 2016
Defence Against Disease
 To understand how the body defends itself against disease
Pathogen Barriers
 Complete the pathogen barriers
worksheet
Pathogen Barriers
Wax traps microorganisms
Tears contain an enzyme
which kills microorganisms
Hairs and mucus stop
micro-organisms from
entering the body
Saliva contains an
enzyme which kills microorganisms
Blood contains white
blood cells which kill any
micro-organisms within
the body
Skin barrier stops microorganisms from entering
the body
Antibody and pathogen cards – find your
matching partner
The antibody will only work if it is connected to this
specially shaped site. This design means that the
antibody does not harm normal body cells because
they do not carry the attachment site.
These are the areas
(antigens) where the
antibody will attach.
White Blood Cells
 There are several different types of white blood cells, each with
different functions, but they can be put into two main groups:  Phagocytes or macrophages
 Lymphocytes
Phagocytes Destroy
Pathogens
Digestive enzymes attack
the ingested microbe and
begin to break it down.
The microbe is destroyed.
The chemicals that are
released from the digested
microbe are used in other
parts of the cell.
Phagocytes
Lymphocytes
 Pathogens contain certain chemicals that are foreign to the body
and are called antigens
 Each lymphocyte carries a specific type of antibody - a protein
that has a chemical 'fit' to a certain antigen
 When a lymphocyte with the appropriate antibody meets the
antigen, the lymphocyte reproduces quickly, and makes many
copies of the antibody that neutralises the pathogen
Antibodies attach
White blood cell
Pathogen
(coated in antigens)
Lymphocytes also release
antitoxins.
1. Producing antitoxins
Remember that microbes can cause an infected person to
feel ill by releasing toxins (poisons). The first way white
blood cells defend the body is by releasing antitoxins. These
chemicals are designed to neutralise the effects of the toxins
and render them harmless.
bacterium
white
blood cell
antitoxins
toxins
Antitoxin links to the toxin and neutralises its effect.
The toxin is now harmless. This happens on a large scale
and reduces the effects of the infection.
Lymphocytes
Fighting Pathogens
 Create a cartoon strip to explain how white blood cells get rid of
pathogens and make you immune…
 Your cartoon should be about the
chicken pox virus and you should try
to explain why you become immune
to the virus after you first get it
skin
Pathogen
Blood vessel
White blood cells
Red blood cells
 White blood cells detect a foreign body and surround it
 White blood cells make antibody against the pathogen. The
antibodies also make the pathogens clump together
Antibody – this is specific to this
particular pathogen
 The antibody acts as a marker for other white blood cells to come
along and engulf the pathogen
White blood cells that
destroy pathogens
 The pathogen has been destroyed and the antibody is left in the
blood stream (active immunity)
 *In passive immunity the body is actually given the antibodies –
this only lasts at most a few years
1. How long did it take to start producing antibodies after the first infection?
2. How long did it take to start producing antibodies after the second infection?
3. Explain why antibodies were produced more quickly after the second
infection.
4. Suggest why the person did not become ill after the second infection.
True or False?
1. Red blood cells defend your body against disease.
2. Antibodies make microorganisms clump together so that they can be
engulfed more easily.
3. Antibodies make antitoxins to destroy the toxins made by
microorganisms.
4. The immune system protects our bodies against infection.
5. Antigens destroy microorganisms by making them clump together.
6. White blood cells make chemicals called antigens.
7. White blood cells destroy microorganisms in five different ways.
8. Microorganism cells have antigens on their outside.
9. An antigen can only recognise and fight one particular microorganism.