Mechanisms of Defence (WJEC GCSE Biology)

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Mechanisms of Defence

  • The human body defends itself against disease in many ways
  • One example is the skin
    • The skin is a structures that make it difficult for pathogens to get into the body
      • It covers almost all parts of your body to prevent infection
      • If the skin is cut or grazed, blood clots form to seal wounds by forming a scab
      • This prevents the entry of pathogens
    • On the surface of the skin is a community of micro-organisms called the skin flora
      • These bacteria compete with any invading pathogenic bacteria preventing them from becoming established
  • If pathogens enter the body, different defence mechanisms are activated
  • For example, through activation of white blood cells
  • Different types of white blood cells work to prevent pathogens from reaching areas of the body they can replicate in
    • Phagocytes engulf and digest pathogenic cells
    • Lymphocytes
      • produce antibodies which clump pathogenic cells together so they can’t move as easily, and release chemicals that signal to other cells that they must be destroyed
      • produce antitoxins which counteract the toxins produced by bacteria

Phagocyte ingesting a pathogen diagram

Phagocytic white blood cells

Phagocytes engulf pathogens and digest them to prevent them causing harm

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Ruth

Author: Ruth

Expertise: Biology

Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. She gained 10 years of teaching experience across the 3 key science disciplines and physical education. Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.