Defense System
Skin is composed of dead cells containing the indigestible protein keratin
Sebum produced by the skin lowers the pH to inhibit growth of pathogens
Lysozymes in salvia, sweat and tears are anti-bacterial enzymes
Many ingested bacteria in the stomach are destroyed by acid (HCl)
A sticky substance, mucus, traps pathogens in the respiratory tract
Cillia moves away mucus towards the throat to protect gas exchange surfaces
The immune system targets foreign materials and pathogens