The blood showing white and red blood cells

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The Body’s Natural Defences

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The Body’s Natural DefencesOur body fights harmful microbes every day Microbes must fight through three levels of our body’s defences before they can cause us harm The first line of defence The second line of defence The third line of defence

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The First Line of Defence

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The First Line of Defence

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The Second Line of Defence

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The Second Line of Defence Non Specific White Blood Cells (Phagocytes)Red blood cells: Carry iron and oxygen around the bodyWhite blood cells: Help fight infectionPlasma: Liquid which carries the blood cells around the body The blood contains

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The blood flows around the body in one direction onlyThe Second Line of Defence Non Specific White Blood Cells (Phagocytes)

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The Second Line of Defence Non Specific White Blood Cells (Phagocytes)If the skin gets damaged, microbes can enter the blood stream and make us ill

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The Second Line of Defence Non Specific White Blood Cells (Phagocytes)The White Blood Cells called ‘phagocytes’ notice anything foreign or strange that gets through the first line of defence and move towards that ‘foreign object’

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The Second Line of Defence Non Specific White Blood Cells (Phagocytes)The phagocytes then surround and destroy the foreign object or, in this case, microbewww.csulb.edu/depts/biology/media/cell751.gif

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The Third line of Defence

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The Third Line of Defence Specific White Blood CellsAll invading cells have distinctive antigens on their surface When the specific white blood cell comes across a microbe, it will a) Make an antibody to match that microbes antigenb) Tell all the other specific white blood cells to make lots of that antibody

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The Third Line of Defence Specific White Blood CellsThe body’s antibodies find their matching antigen on the harmful microbes and lock on to them

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The Third Line of Defence Specific White Blood CellsThe antibodies will then a) Mark the harmful microbes for destruction b) Stay in the blood after the harmful microbes have been killed ready to fight them if they should ever return

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Last Updated: 8th March 2018

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