this is bout body defenses

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

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

4. 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

5.  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. • inflammatory response
– (before inflammation : skin arterioles constrict to
prevent excessive bleeding)
– skin arterioles in the infected area dilates so that
more blood flows to the area
– the permeability of skin capillaries increases so
that more phagocytes & fluid come into the
infected tissues
– the skin becomes red & swell up with pain
(because of high pressure)
Nonspecific
(after infection)

19. Specific
Defences

20. 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

21. • 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

22. • 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

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

24. 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

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

26. Small pox (a killing disease)

27. Vaccine (Vaccination)

28. Vaccine (Vaccination)
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

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

31. ~END~