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Defence Against Microbes

Defence Against Microbes. Introduction Microbes are found everywhere – in the soil, in water, in the air and in our food. They inhabit our shin and in our gut. Why aren’t we continually affected by microbes? How do we stop them invading our internal organs and bloodstream?

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Defence Against Microbes

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  1. Defence Against Microbes

  2. Introduction • Microbes are found everywhere – in the soil, in water, in the air and in our food. They inhabit our shin and in our gut. • Why aren’t we continually affected by microbes? • How do we stop them invading our internal organs and bloodstream? • The body is protected by a complex system of defences that prevent assault from pathogens. • The body defences: • Prevent microbes getting in through the body’s entry points • Destroy microbes once they’ve got in

  3. 1st Line of Defence Non-specific physical & chemical barriers Physical Barriers • Keratin in cells of the outer layer of skin cells makes it tough & virtually impermeable to microbes • Membranes lining the inner surfaces of the body produce mucus that traps invading microbes • Cilia line the respiratory airways and beat constantly, pushing microbes trapped in the mucus up to the throat where it is swallowed or coughed out • The normal flora or the body (in the skin, gut, & vagina), compete with potential pathogens for space & food • Coughing & sneezing help to eject microbes out of the airways • Bleeding, urinating and vomiting flush microbes out

  4. 1st Line of Defence Non-specific physical & chemical barriers Chemical Barriers Anti-microbial substances in secreted body fluids thet either kill or inhibit the growth of microbes • Sebum (oil) produced by the skin’s sebaceous glands • Hydrochloric acid secreted by the cells lining the stomach • Lactic acid produced by the natural flora of the vagina(hence the use of natural yoghurt to treat thrush!) • Lysozyme enzyme found in tears, saliva & mucus

  5. 2nd Line of Defence Non-specific immune system This is activated when microbes invade the body. It is ‘non-specific’ as the response is the same for allpathogens Phagocytes, a type of white blood cell, ingest & digest invading microbes

  6. antigens on the surface pathogen 3rd Line of Defence Specific immune system A specific response occurs when the immune system recognizes an antigen on the surface of a microbe that does not belong in the body, and then prepares a specific reaction to it, an ANTIBODY. Specific antibodies bind to specific antigens and cause there destruction.

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