Defense against Infectious Diseases

How white blood cells work to comabt and prevent disease. CCEA revised chapter 15

  • Created by: Abigail
  • Created on: 13-06-13 15:52

Defense Against Disease


Provides an excellent barrier to microorganisms

Mucous Membranes

Trap microorganisms and prevent them going any further


Stops more blood escaping but also acts as a barrier against infection

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Antigens and Antibodies

  • Microbes have protein markers (anitgens) on their cells that alert special white blood cells (lympocytes) to produce antbodies
  • Lymphocytes produce antibodies which join with the microorganism to clump together and become immobilised
  • Antigens and antibodies are complementory 
  • As each microorganism has different antigens on its surface, different shapes of antibodies are produced for each microorganism
  • Clumping of the disease microbes results in reduced spread of the disease microbe and reduces symptoms of the disease
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1. Phagocyte surrounds and engulfs the bacteria

2. Phagocyte releases chemicals which digest and destroy the microorganism

3. Waste material is released out of the phagocyte which is then expelled out of the body

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How body deals with invading Microorganisms

1. Microorganism enters the blood

2. Antigens cause lymphocytes to produce antibodies

3. Antibodies join with the microorganism causing them to clump together and become immobilised

4. The phagocytes surround and engulf the microorganism

5. Chemicals inside the phagocyte digest the microorganism, destroying it

6. Waste material is released out of the phagocyte and expelled out of the body

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