Innate immunity Mechanical barriers Physical barriers Chemical barriers

Innate immunity - Mechanical barriers. - Physical barriers. - Chemical barriers. - Cellular barriers. - Inflammation Dr. Iman Ibrahim and Dr. Sultan Alsharif

TYPES OF IMMUNITY Natural / Innate Immunity Acquired / Adaptive Immunity Dr. Iman Ibrahim and Dr. Sultan Alsharif

Dr. Iman Ibrahim and Dr. Sultan Alsharif

helper, killer, regulatory Dr. Iman Ibrahim and Dr. Sultan Alsharif

Innate Immunity • first line of defense against invasion by microbes • not acquired through contact with a foreign substance known as an antigen • Eg: phagocytosis by leukocytes & natural killer cells Dr. Iman Ibrahim and Dr. Sultan Alsharif

Mechanical barriers - Ciliated epithelial cells lining the trachea removing inhaled microbes - Mucus secreted by these cells prevent the microbes from associating closely with the cells - Cilia push microbes upwards until they are caught in oral secretions and expectorated or swallowed Dr. Iman Ibrahim and Dr. Sultan Alsharif

Physical barriers The skin The structural integrity of tissue surfaces = barrier to penetration by microbes Intact surfaces prevent potential pathogens from adhering to surfaces Sebaceous glands secrete fatty acids and lactic acid which lower the skin p. H (p. H 4 -6) Dr. Iman Ibrahim and Dr. Sultan Alsharif

Chemical barriers • • Saliva Tears contains antibacterial substances • - Stomach HCl The p. H of the stomach is 2. 0 which is too low for most pathogens • Large intestine contain large number of bacteria Dr. Iman Ibrahim and Dr. Sultan Alsharif 33

Normal Flora of the Gastrointestinal Tract Dr. Iman Ibrahim and Dr. Sultan Alsharif