GCSE Combined Science (AQA)

622 videos | 38 hours

Non-Specific Defence Systems

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Infection and Response Communicable Diseases

Non-Specific Defence Systems

3:43 Fighting Communicable Diseases
Spec 4.3.1.6
Previous Malaria Next Immune System
  • The body has non-specific defense systems to protect against general pathogens.
  • These systems aim to prevent any pathogen from entering the body by providing an initial barrier.
  • The first line of defense in humans is non-specific and involves physical and chemical barriers.
  • The skin is the main barrier, covering the entire body and preventing pathogens from reaching underlying tissues.
  • The skin also releases antimicrobial secretions that destroy harmful bacteria.
  • If the skin barrier is broken, platelets in the blood form a clot to seal the wound and prevent further pathogen entry and blood loss.
  • Areas of the body not covered by skin have other defenses such as tears and saliva, which contain antibacterial enzymes like lysozyme.
  • The nose has hairs and mucus that filter out pathogens and prevent them from entering the respiratory system.
  • If pathogens bypass these barriers, they are trapped in mucus produced by cells lining the trachea and bronchi.
  • Cilia, tiny hair-like projections, move the mucus to the back of the throat where it is swallowed.
  • Stomach acid then destroys the pathogens contained in the swallowed mucus.

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