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First-Line Defenses: Chemical Barriers definitions

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  • Sebum
    Oily substance from sebaceous glands that lowers skin pH and inhibits microbial growth by creating an acidic environment.
  • Sweat
    Fluid secreted by skin glands containing lysozyme and other chemicals that remove microbes and lower body temperature.
  • Earwax
    Complex mixture in the ear canal that traps microbes, lowers pH, and contains antimicrobial chemicals for dual barrier protection.
  • Saliva
    Oral fluid rich in enzymes like lysozyme that inhibit microbial growth and prevent colonization in the mouth.
  • Gastric Juice
    Highly acidic stomach secretion with hydrochloric acid and enzymes that kills ingested bacteria and inactivates toxins.
  • Antimicrobial Peptides
    Short amino acid chains produced by epithelial cells that disrupt microbial membranes, leading to cell lysis.
  • Lysozyme
    Enzyme present in body fluids that degrades bacterial cell walls, providing protection across multiple body sites.
  • Sebaceous Glands
    Skin structures that secrete sebum, contributing to the skin's chemical defense by lowering pH.
  • Defensins
    Positively charged antimicrobial peptides that insert into microbial membranes, causing lysis and protecting skin and mucosa.
  • pH
    Measurement of acidity or alkalinity; lowering it in body secretions inhibits microbial survival and growth.
  • Epithelial Cells
    Cells lining body surfaces that produce antimicrobial peptides to protect against infection.
  • Hydrochloric Acid
    Strong acid in gastric juice responsible for the stomach's low pH and destruction of most ingested microbes.
  • Keratin
    Protein in ear canal skin cells that creates a dry environment, further inhibiting microbial growth.
  • Innate Immunity
    Non-specific defense system including physical and chemical barriers that provide immediate protection against pathogens.
  • Perspiration
    Process of sweat release that removes microbes from skin and contributes to chemical defense.