3. Pathogens  Microorganisms causing diseases  eg. bacteria viruses fungi protozoa

4. Importance of having Body Defense System  prevent pathogens from entering the body  kill or inactivate any pathogens that gain entry into the body

5. Ways of Pathogen spreading  In Droplets e.g. influenza, cold  By Touch e.g. boils, athlete’s foot, AIDS, anthrax  By Dust e.g. diphtheria, scarlet fever, anthrax, hay fever

6.  In Faeces e.g. cholera, hepatitis A  In Food e.g. salmonella  By Insect e.g. malaria  By Vertebrates e.g. rabies Ways of Pathogen spreading

7. Nonspecific Defences

8. physical barrier  Skin  the 1st line of defence of pathogen  Ciliated & Mucus Lining of respiratory tract  mucus: trap bacteria  beating cilia: waft the trapped bacteria towards the throat Barriers

9. chemical barrier  sebaceous glands of skin  produce oily secretion (sebum) which has antiseptic properties  tears & saliva  contain lysozymes (enzyme) which destroy bacteria Barriers

10.  gastric juice in stomach  contain acid which can destroy most bacteria  acid secretions in vagina of women  reduce growth of pathogens chemical barrier Barriers

11. When you cut yourself carelessly, why the wound stop bleeding after a while ? ∵ Blood Clotting occurs: Platelets release a substance to turn soluble fibrinogen into insoluble fibrin which catches blood cells & seal off the cut

12. Insoluble fibrin

13. BLOOD CLOTTING is important because this can …  Prevent the body from invasion of pathogens  Stop excess bleeding (blood loss)

14. Nonspecific (after infection) to localize & destroy the pathogens phagocytes involve in phagocytosis –to engulf and digest the pathogens macrophage

17. Specific Defences

18. What are Specific Defences ? When a pathogen is able to get past the nonspecific defences, immune responses will be produced which involve a series of specific defences

19. After pathogens get into the blood & lymph : Antigens on the surface of pathogen stimulate lymphocytes in the lymph nodes and the blood. – to produce specific antibodies which kill pathogen by : » lysis - burst the pathogen » clump the pathogen together

20. After pathogens get into the blood & lymph : Antigens on the surface of pathogen stimulate lymphocytes – to produce specific antibodies which kill pathogen by : » stick to the surface of pathogen, so that phagocytes can ingest them easily (enhanced phagocytosis) » neutralize the toxins from pathogens

21. Primary & Secondary Immunity Responses Primary Response: the 1st time invaded by a certain pathogen which stimulates the body to produce antibodies

22. Primary & Secondary Immunity Responses Secondary Response: the invasion of the same type of pathogen which stimulates lymphocytes to produce much larger amount of antibodies & much more quickly

23. Time (days) antibody conc. immune response no immune response primary response secondary response second exposure to antigen X first exposure to antigen X

24. Small pox (a killing disease)

25. Vaccine (Vaccination)

26.  From dead / weakened pathogens –to stimulate the lymphocytes to produce antibodies  Times of injection: –first→ second → (booster) injection  From injection of a serum  It belongs to acquired immunity

27. Injection of a Serum immune response no immune response antibody conc. Time (days) injection of antibody (in serum)

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