UNIT 3 - KA5
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Describe what is meant by pathogen
A pathogen is a bacterium, virus or other organism that can cause disease
What are the three lines of defence against infection by a pathogen
1- physical and chemical barriers to infection 2- non specific cellular defences 3- specific cellular defences
Explain the term non - specific in relation to immunity
This type of immunity is directed against any pathogen/cell- doesn’t matter what it is
Describe how epithelial surfaces offer physical protection against pathogens.
• epithelial cells form a physical barrier • closely-packed epithelial cells are found in the skin and inner lining of the digestive and respiratory systems
Which type of secretions are produced against invading pathogens
Chemical secretions are produced against invading pathogens
Which chemical secretions are produced against invading pathogens
Secretions include tears, saliva, mucus and stomach acid
How does the body response to a physical injury or invasion by microorganisms
When the body suffers from physical injury such as cut and/or invasion by microorganisms, it responds with a defence mechanism called the inflammatory response
Which cells initiate the inflammatory response
A group of immune cells called mast cells are responsible for initiating this response
What chemical is released by mast cells during the inflammatory response
Histamine is released by mast cells during the inflammatory response
What are the two effects of histamine on the body
• causing blood vessels (small arteries) in the injured area to vasodilate • blood capillary walls become more permeable (leaky)
What are the benefits of increased blood flow and capillary permeability during the inflammatory response
The increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection.
The inflammatory response - summary
Histamine is released by mast cells causing vasodilation and increased capillary permeability. The increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection.
What do phagocytes do to pathogens
Phagocytes recognise pathogens and destroy them by phagocytosis
Brief description of the process of phagocytosis
Phagocytosis involves the engulfing of pathogens and their destruction by digestive enzymes contained in lysosomes
What do phagocytes release
Phagocytes release cytokines which attract more phagocytes to the site of infection
What are cytokines
Cytokines are protein molecules that act as a signal to specific white blood cells causing them to accumulate at the site of infection