1. Body Defence Skin Ciliated inner lining of the respiratory Tract
Physical and Chemical Barriers:
Skin
Ciliated inner lining of the respiratory Tract
Gastric juice

2. Skin The outer layer of the skin is :
Tough conrnified layers of epidermis
Epithelium made of water-proof protein
It is a mechanical barrier

3. Skin (Con’t) To prevent the entry of bacteria
Virus and protozoan from entering through the skin

4. Ciliated lining of the respiratory tract
Filtering bacteria and particulate
Sweep the mucus that trapped the bacteria and the particulate

5. Gastric Juice Mainly composed of hydrochloric acid (HCL)
Kill the pathogens that are ingested

6. Function of Blood in body defence
There are white blood cells and antibodies
Phagocytes > Engulf Bacteria
Lymphocytes >Produce antibodies

7. Hematopoietic stem cells produce cells in blood and lymph
(Adapted from Biology of the Immune System, JAMA 278 (22))

8. Phagocytes Pathogen enter the damaged skin and cause inflammation.
Capillary wall dilate and more permeable for the blood flow to the infected area.
Phagocyte abundant in blood

9. Phagocytes (Con’t) move to the infected area by amoeboid movement,
engulf bacteria, germs or foreign substance and digest them
Phagocyte and pathogens usually form pus.

10. Lymphocytes Some pathogens can kill phagocytes.
Pathogens stimulate the lymphocyte to produce antibodies (protein) which specifically to the them.

11. Lymphocytes (Con’t)
Cause the pathogen to burst, to clump or to stick together
Pathogens can be engulf or ingest by phagocyte more easily

12. Lymphocytes (Con’t)
Produce antibodies that are readily to kill the germs (which as antigen)
To neutralize the toxin secreted by the germs.

13. Process of vaccination
achieves by the injection of small amounts of antigen (the vaccines ) into the body of an individual

14. Process of vaccination
then triggers the immune response(s) (antibodies production/phagocytes proliferation) of the individual without causing the disease
antigen
antibodies
phagocyte

15. Process of vaccination
a second, booster injection is often needed to stimulates a much quicker antibody production

16. Process of vaccination
time
Antibody level
first injection
second injection
immune
no immune

17. Process of vaccination
after eliminating the injected antigen, some of the antibody-producing cells would remain in the body for memorizing the disease

18. Process of vaccination
once the antigen enters the individual again, the individual can initiate immune response much more quickly which protects the individual from the disease

19. Principle of vaccination
Induced Antibodies Production
specific (work against particular antigen)
Phagocytes Proliferation
nonspecific

20. Type of immunity Natural Passive Acquired Passive Natural Active
Acquired Active

21. Blood Clotting Importance prevents further blood loss
prevents the entry of pathogenic micro-organisms