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Blood clotting mechanism

Posted by Mumtaz khan Friday, 21 October 2011

        Clotting is a much complex process in which all the coagulation factor must synchronize and activate each other.Basically the entire mechanism of clotting can be explained in 3 steps.
1. Formation of Prothombinase .
2. Conversion of plasma protein-prothombin into an enzyme called Thrombin by the activator-Prothombinase.
3. Conversion of another plasma protein called Fibrinogen which is soluble,into insoluble Fibrin under the influence of Thrombin.

The extrinsic pathway of blood clotting has few steps as compared to the intrinsic pathway .This is because of clotting comes into play.When there is a severe trauma and occurs rapidly.It has been named Extrinsic because a tissue factor which is a tissue protein i.e.,coagulation factor III popularly referred as Thromboplastin leaks into the blood from the tissue cells which are outside the blood vessels(so extrinsic).This coagulation factor III is a complex mixture of Lipoprotein and phospholipid which gets released from the surface of damaged cells.Since the factor is released from the site of injury itself the 3 stage process of clotting will be rapid.This Thromboplastin activates coagulation factor VII in presence of Calcium ions.Coagulation factor VII gets activated w+hich again in the presence of Calcium ions activates CF X.Once CF X is activated it combines w+ithCF V again in the presence of Calcium ions form active enzyme Prothombinase.Formation of Prothombinase satisfies the 1st stage process in blood clotting.
Stage 2 and stage 3 processes i.e.,conversion of plasma protein Prothrombin into enzyme Thrombin by using prothrombinase and finally conversion of soluble plasma proteins fibrinogen into insoluble threads fibrin by using thrombin are the next steps completing the Extrinsic pathway.


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