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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

Type of immunity Natural Passive Acquired Passive Natural Active Acquired Active

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