HUMAN ANATOMY AND PHYSIOLOGY

 MECHANISM OF CLOTTING PART 02

In another mechanism the tissue lying adjacent to blood gets damaged and releases certain factors these factors are mixed with calcium and plasma to activate prothrombin this is extrinsic system of activation 
        In short extrinsic system is initiated by damaged tissue while intrinsic system is initiated by blood itself extrinsic system is faster (1-2 min) as compared to intrinsic system which takes about 4-8 min 
In third step the active thrombin acts on soluble fibrinogen present in plasma to convert it into soluble fibrin monomers and fibrin peptides this is finally converted into insoluble cross linked fibrin polymer (the clot) in the presence if fibrin stabilizing factor (factor13)
    The clot is further stabilised when thromboplastin a contractile protein released from platelets causes it to retract 
        Clot removal is normally initiated by a proteolytic enzyme plasmin whose precursor plasminogen is abundant in plasma 

Importance of clot: 

Blood clotting is of vital importance because it checks bleeding if there is no clotting any little haemorrhage would result in bleeding that would continue till death in fact men and more so women would all die of bleeding this life saving device of clotting is however a double edged weapon in old age intravascular clotting occurs as a disease and gives rise to heart attacks paralysis unconsciousness and even death 

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