first line of defense

• First line of defense including physical and chemical barriers
• What include in first line of defense?

  Physical and chemical barriers
• Physical barriers are skin and mucous membrane
• Skin: nearly impenetrable, waterproof, resistant to most toxins and enzymes of invading organisms
• Mucous membranes: line the respiratory and digestive tracts; sticky mucus traps microbes
• Chemical barriers are sweat and oil glands of the skin; lining of the stomach; urine; saliva, and tears
• Sweat and oil glands of the skin produce chemicals that slow or prevent the growth of bacteria
• The lining of the stomach produces hydrochloric and protein-digesting enzymes that destroy pathogens
• Urine slows bacterial growth with acidity and flushes microbes from the urethra
• Saliva and tears contain a lysozyme -an enzyme that kills bacteria