Barriers to Pathogens: Skin & Mucous Membranes (DP IB Biology)

Skin as a Barrier to Pathogens

• 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 that usually cause no issues, as they can't enter the body. Skin provides:

  • A tough physical barrier that prevents entry of pathogens into our bodies

  • Cuts in the skin are sealed by formation of blood clots to prevent entry of pathogens

  • Chemical protection through the production of sebum from the sebaceous glands of the hair follicles

    • Sebum is a chemical responsible for maintaining a low 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 mucus containing glycoproteins

  • Microorganisms and particles become trapped by the mucus

  • The mucus is then swept along by the cilia of the ciliated epithelium upwards and is swallowed

  • The mucus and any microorganisms will then be swallowed and destroyed by the acid in the stomach or expelled, therefore preventing infection

  • Mucus also contains lysozyme enzymes which have antibacterial properties, providing more protection from invading microorganisms

Cilia and Goblet Cells Diagram

Ciliated epithelium contains cilia, a basement membrane, and goblet cells