IB Biology SL

Revision Notes

6.3.1 Skin


  • The skin and mucous membranes form a primary defence against pathogens that cause infectious disease
  • Skin is the largest organ of the body and is covered in microorganisms which usually cause no issues, as they can’t enter the body. Skin provides:
    • A tough physical barrier which prevents entry of pathogens into our bodies
    • Chemical protection through production of sebum from the sebaceous glands of the hair follicles
      • Sebum is a chemical responsible for maintaining a lower skin pH which inhibits the growth of microorganisms
  • Mucous membranes are found lining vulnerable areas which may be a route for pathogens into the body.
  • This includes the airways, areas around the reproductive organs (foreskin and vagina) and the digestive system
  • The membranes contain goblet cells which produce mucous containing glycoproteins
    • Microorganisms and particles become trapped by the mucous and are then either swallowed (into the stomach) or expelled, therefore preventing infection
    • Mucous also contains lysozyme enzymes which have antibacterial properties, providing more protection from invading microorganisms

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