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Body defence systems

First line defence

  • skin: dry dead outer cells are difficult to penetrate, sebaceous glands produce oils that kill micro-organisms
  • Respiratory system: nasal passage has mucus and cilia whiich catch dust and bacteria before they reach the lungs
  • eyes: tears- lysozyme destroys micro-organisms 

Second line defence 

phagocytes: detect and engluf any foreign particles such as microbes.

phagocytes are non specific so will attack anything thats not meant to be there

also trigger an inflammatory response which increases blood flow to infected are in order to allow plasma to leak into damaged tissue so that the right cells can fight the infection.

final line of defence

lymphocytes: B-cells which recognise particular antigens which then activates an immune response to attatch to the antigen and destroy it.

T-cells are in the lymphocytes and stick around after the infection has been fought so that of it eneters again they can reproduce very fastly to the antigen. 

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transmission of pathogens

direct contact

horizontal: passed on from touching, kissing or sexual intercourse 

vertical: passes on from mother to baby through placenta 

indirect contact

vehicle borne transmission: object carrying a diseas to people

vector borne: animal carries the microorganisms to people

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plant defences

antibacterial plants 

mint plant: antibacterial properties

witch hazel:prevents infections getting through skin 

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