BIOL 1221 Lecture Notes - Lecture 13: Natural Killer Cell, Adaptive Immune System, Humoral Immunity
22 Jun 2017
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Document Summary
1st line of defence -skin and mucosae. Skin and mucous membranes , and their secretions: Keratin is resistant to weak acids and bases, bacterial enzymes, and toxins. Mucous membrane line all body cavities open to the exterior: the digestive, respiratory, urinary, and reproductive tracts. Skin and mucous membranes produce protective chemicals that inhibit or destroy microorganisms. Acid: acidity of skin and some mucous secretions inhibits growth. Enzymes: lysozyme of saliva, respiratory mucus, and lacrimal fluid kills many microorganisms; enzymes in stomach kill many microorganisms. Mucin: sticky mucus that lines digestive and respiratory tract traps microorganisms. Other chemicals: lipids in sebum and dermicidin in sweat are toxic to some bacteria. 2nd line of defence -(innate internal defences are cells and chemicals that act as the second line of defense). Various cells and chemicals protect against pathogens that breach the surface barriers: phagocytes, natural killer ( nk ) cells.
