defense again disease

• External Defenses


  • Barriers preventing pathogens from entering the body
• Skin


  • A physical barrier that pathogens cannot pass though
  • Sweat kills pathogens
  • Local fauna (bacteria) that attacks invading pathogens
• Eyes


  • Eyelids, eye lashes and eyebrows - physical barriers blocking pathogens from entering eyes
  • Tears contain lysozyme (an enzyme) and salt - kills pathogens
• Ear


  • Cerumen (ear wax) - physical barrier that traps pathogens and pushes them out of the ear
  • Hairs - physical barrier
• Nasal Cavity


  • Nose hairs and mucus - physical barrier preventing pathogen from entering the respiratory system
• Trachea and Bronchi


  • Mucous and Cilia - physical barrier that traps pathogens and removes them from respiratory system
• Oral Cavity


  • Mucous membranes - trap pathogens
  • Saliva contains acid that kills pathogens
• Stomach


  • Acid - kills pathogens and prevents infection of digestive system
• Urethra


  • Urine - kills pathogens and pushes them out of the urinary system (and reproductive system in men)
• Vagina


  • Acidic secretions - kill pathogens and prevent infection of reproductive system (in females)
  • Labia - physical barrier preventing pathogen from entering
• Anus


  • Mucus membranes - trap pathogens preventing infection of the digestive system
• Internal defenses


  • Non-specific defenses that fight pathogens if they breach the external defenses
• PHAGOCYTES

  • Cells engulf and digest pathogens using phagocytosis
  • Leucocytes - white blood cells (either produce chemicals to kill pathogens or phagocytose them)
  • Macrophages - large cells that phagocytose pathogens
• the LYMPHATIC SYSTEM


  • Consists of a network of lymph vessels containing lymph, and lymph nodes
  • Prevent infection by sending phagocytes to tissues to kill pathogens