The body’s defence systems against microbial diseases

First line

• Skin – generally dry – wounds healed after blood clots
• Nasal hairs – trap larger particles
• Cilia in the respiratory system act together with mucus to trap smaller particles e.g. bacteria and pass these into the digestive system for disposal by acids and enzymes.
• Lysozyme is an enzyme, found in many body fluids e.g. tears, that breaks down cell walls of many bacteria

Second line

• Phagocytes (white blood cells) detect and engulf any thing “foreign” to the body, e.g. invading bacteria, and digest them
• The inflammatory response due to increased blood flow causes swelling and heat and increases contact with white blood cells

Third line