Human Body Defences and Pathogens
Think of your body as a fortress with multiple layers of protection against invaders. Your non-specific defences work like the outer walls - they stop most threats before they even get inside. Your skin acts as a waterproof barrier, whilst mucus in your respiratory system traps pathogens trying to enter through your airways.
Your body's got some clever chemical warfare too. Tears contain enzymes that destroy pathogens threatening your eyes, and your stomach produces hydrochloric acid that kills most nasties you accidentally swallow. Even your skin hosts good bacteria that crowd out the harmful ones.
Pathogens are disease-causing microorganisms including bacteria, viruses, fungi, and protists. Communicable diseases spread from person to person through direct contact, air, water, contaminated food, or vectors like mosquitoes. Non-communicable diseases, however, can't be passed between people.
Key Insight: Your body's first line of defence works 24/7 without you even thinking about it - pretty impressive for something you never have to consciously control!