When the physical barrier is breached

Damage to the physical barriers generates a point of entry for pathogens and, in addition, risks the loss of blood. The 

Functional Biochemistry in Health and Disease by Eric Newsholme and Tony Leech 2010 John Wiley Sons Ltd 

CH 17 DEFENCE AGAINST PATHOGENS BARRIERS, ENZYMES AND THE IMMUNE SYSTEM 

Blood clotting first received serious scientific attention in the seventeenth century, when Malpighi and BoreUi proposed that a blood clot was formed from the fluid part of the blood. In the eighteenth century, John Hunter established that clots were formed from the coagulable lymph . In 1845, Buchanan showed that a series of enzymes was involved and by 1900 it was accepted that the soluble substance in blood, fibrinogen, was converted into the solid fibrin clot by an enzyme, thrombin. From that time many 

Haemophilia is characterised by repeated, spontaneous and traumatic haemorrhages. It is divided into two classes, haemophilia A and haemophilia B. 

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