4. Often we recognise by the symptoms it causes. The immune response is not so obvious, until we recover

identify defence barriers to prevent entry of pathogens in humans:1ST LINE OF DEFENCE  (6) -SKIN: Description: the skin continuously grows by new cells being produced from below. Cells fit tightly together to from a protective layer covered by dead cells. Function:  unbroken skin prevents entry of pathogens lack of water makes it hard for pathogens to live on constant flaking carries microbes away -MUCUS MEMBRANE: Description: in the lining of the digestive, reproductive, respiratory and urinary ducts. Provides a think viscous mucus which traps pathogens Function: sticky and traps pathogens more pathogens causes for more mucus to flush them out can contain the antibody IgA which prevents attachment of microbes mechanisms such as cilia and sneezing help remove mucus and trapped pathogens -CILIA: Description: hair-like projections from cells lining the air passages (trachea and bronchial tubes) Function: move with wave-like beating motion to push mucus containing pathogens from the lungs to throat, where removed by sneezing or coughing -CHEMICAL BARRIERS Description: different chemicals are in different parts of the body (acid in stomach, alkali in small intestine, the enzyme lysosome in the tears) Function: stomach acid destroys pathogens alkali destoyrs acid resistant pathogens lysosome dissolves cell wall of bacteria -OTHER BODY SECRETIONS Description: secretions from sweat glands   oily secretions from glands in hair   tears cleanse eyes   urine flushes out urinary tract. Function: contain chemicals that destroy bacteria and fungi 

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