Defense Systems

• Nonspecific defense system


  The body's first line of defense against pathogens, preventing them from entering the body
• Parts of the nonspecific defense system

  • Skin
  • Nose and mucus
  • Cilia in trachea and bronchi
  • Stomach acid
• Skin


  • Forms a protective layer covering the body
  • Outer layer of dead cells difficult for pathogens to penetrate
  • Produces sebum to kill bacteria
  • Can scab over when damaged to prevent pathogen entry
• Nose and mucus


  • Contract pathogens before they enter the breathing system
• Cilia in trachea and bronchi

  • Covered in mucus, contract pathogens upwards towards the throat to be swallowed
• Stomach acid


  • Kills pathogens before they can travel further down the digestive system
• Even with the nonspecific defense systems, pathogens can still get into the human body and cause serious disease, so the immune system also protects us
• Immune system


  Protects us against pathogens
• Immune system


  • Destroys pathogens and any toxins they produce
  • Protects us in case the same type of pathogen invades us again in the future
• White blood cells


  Involved in the immune system
• How white blood cells destroy pathogens

  1. Detect chemicals released from pathogen

  2. Ingest pathogen

  3. Use enzymes to destroy pathogen
• Phagocytosis


  The process of white blood cells ingesting and destroying pathogens
• How white blood cells destroy pathogens using antibodies

  1. White blood cells produce antibodies

  2. Antibodies stick to pathogens

  3. This triggers the pathogens to be destroyed
• Antibodies


  • Extremely specific to one type of pathogen
  • Can remain in the blood for a long time to protect against future infection
• How white blood cells protect against toxins

  1. White blood cells produce antitoxins

  2. Antitoxins stick to toxin molecules

  3. Prevents toxins from damaging cells
• You'll find plenty of questions on the immune system in the revision workbook