Primary lines of Defence

Primary lines of Defence

1. Skin

   • Impermeable to most pathogens
     • Some can penetrate
       • Viruses that create warts
   • 'Flora' of harmless bacteria
     • Live on healthy skin
   • Most pathogenic bacteria cannot survive in skin
     • Lactic + fatty acids secreted by sweat glands
       • pH is too low for them
   • Damaged skin is an entrance for harmful bacteria
     • Underlying tissue
     • Blood clotting seals wounds quickly

2. Vagina

   • Bacterium keep pH low by secreting lactic acid
     • These bacteria can be killed by using antibiotics
       • pH of vagina rises, allowing other microorganisms to multiply more

3. Eyes + Mouth

   • Bathed in fluids which have bactericidal action
     • Lysozyme
       • Saliva + Tears
       • Enzyme that destroys/damages many bacteria

4. Semen

   • Spermine

5. Breast milk

   • Lactoperoxidase

6. Stomach

   • Hydrochloric acid
     • Destroys/damages bacteria ingested in food

7. Mucus

   • Protects digestive and respiratory tracts from infection
     • Barrier
       • Bacteria cannot make contact with epithelial cells lining walls of tubes
     • Traps bacteria and other particles
   • Produced by goblet cells