immune system

• Physical and chemical barriers

  Stop pathogens from getting into the body
• Immune system


  Destroys pathogens that make it into the body
• Skin


  • Acts as a physical barrier that pathogens can't get through
  • Secretes oils and antimicrobial substances that can kill pathogens
• Nose


  Has hairs and mucus that trap pathogens and particles in the air
• Trachea and esophagus


  Only two tubes leaving the throat that pathogens can enter
• Trachea, bronchi, and bronchioles

  1. Covered in mucus that traps particles

  2. Lined with cilia that move mucus and trapped particles up to the throat to be swallowed
• Stomach acid


  Hydrochloric acid that kills most pathogens
• Immune system


  • White blood cells that patrol the body
  • Phagocytosis - white blood cells engulf and destroy pathogens
  • Produce antitoxins to counteract toxins from pathogens
  • Produce antibodies specific to antigens on pathogens
• Antigens


  Substances detected as foreign by the immune system, such as bacterial cell walls or viral proteins
• Antibodies


  Proteins made by white blood cells that can bind to specific antigens and signal for their destruction
• Immune system remembers pathogens

  Produces many antibodies quickly to destroy pathogens before they can develop
• The body survives millions of pathogens attacking it every day