3.1.6: Human defence systems
Not started yet — this one needs some love.
Non-specific physical/chemical defences:
Skin: barrier preventing pathogen entry; sebum has antibacterial properties.
Nose: mucus and hairs trap pathogens.
Trachea and bronchi: cilia and mucus trap pathogens; cilia sweep mucus (with trapped pathogens) up to throat.
Stomach: acid (low pH) kills pathogens.
Specific immune response (white blood cells):
Phagocytosis: phagocytes (a type of white blood cell) engulf and digest pathogens; does NOT produce antibodies.
Antibody production: lymphocytes (a type of white blood cell) produce specific antibodies that bind to antigens (proteins) on the pathogen's surface → marks pathogen for destruction.
Antitoxin production: lymphocytes produce antitoxins that neutralise toxins produced by bacteria.
Common exam mistakes
Antigens are proteins on the surface of pathogens; antibodies are proteins produced by lymphocytes to bind to antigens — do NOT confuse these terms. Antigens trigger the production of specific antibodies.
Phagocytosis (engulfing pathogens) is done by phagocytes; antibody production (binding to antigens) is done by lymphocytes — these are DIFFERENT white blood cell types with DIFFERENT roles.
Antitoxins are produced by lymphocytes and neutralise specific toxins; antibodies are produced by lymphocytes and bind to antigens on pathogen surfaces — both are made by lymphocytes but serve different purposes.
Do NOT say 'white blood cells produce antibodies' without specifying lymphocytes — phagocytes do not produce antibodies.
The cilia sweeping mechanism is specific to the trachea/bronchi — the stomach uses acid (not cilia or mucus) to kill pathogens.