DEFENCES

• physical barrier: skin secretes oils
• physical barrier: hair and mucus in the nose trap particles
• physical barrier: trachea and bronchi screte mucus to trap pathogens
• physical barrier: cilia wafts mucus up the throat then can be swallowed
• chemical barrier: hydrochloric acid in stomach
• chemical barrier: tears contain enzymes
• white blood cells travel in the blood and patrol for microbes
• white blood cells attack by: engulfing them (phagocytosis)
• white blood cells attack by: producing antitoxins counteracting toxins produces by lymphocytes
• white blood cells attack by: producing antibodies- when white blood cells come across foreign antigens they produce proteins to lock on invading cells
• antibodies are specific to the antigen
• antibodies reproduce rapidly
• disease is reduced by: good hygiene, destroying vectors, isolating infected, vaccinations
• vaccines- injecting small amount of inactive pathogens which carry antigens causing the body to produce antibodies