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Need to know the stages and what happens in each stage, what cells/tissue are active in each.

2007-02-11 14:38:26 · 2 answers · asked by Anonymous in Science & Mathematics Biology

2 answers

The coagulation cascade can be summarised as follows:
PROTHROMBIN,THROMBOPLASTIN,THROMBIN(CLOT)

Tissue Factor pathway: the main role of the tissue factor pathway is to generate a "thrombin burst," thrombin being the single most important constituent of the coagulation cascade in terms of its feedback activation roles. FVIIa circulates in a higher amount than any other activated coagulation factor. Following damage to the blood vessel, endothelium Tissue Factor (TF) is released, forming a complex with FVIIa (TF-FVIIa), which activates FIX and FX. FVII itself is activated by thrombin, FXIa, plasmin, FXII and FXa. The activation of FXa by TF-FVIIa is almost immediately inhibited by tissue factor pathway inhibitor (TFPI). FXa and its co-factor FVa form the prothrombinase complex which activates prothrombin to thrombin. Thrombin then activates other components of the coagulation cascade, including FV and FVII (which activates FXI which in turn activates FIX), and activates and releases FVIII from being bound to vWF. FVIIIa is the co-factor of FIXa and together they form the "tenase" complex which activates FX and so the cycle continues.
Contact Activation pathway: There is formation of the primary complex on collagen by high molecular weight kininogen (HMWK), prekallikrein and FXII (Hageman factor). Prekallikrein is converted to kallikrein and FXII becomes FXIIa. FXIIa converts FXI into FXIa. Factor XIa activates FIX, which with its co-factor FVIIIa form the tenase complex which activates FX to FXa. The minor role that the contact activation pathway has in initiating clot formation can be illustrated by the fact that patients with severe deficiencies of FXII, HMWK and prekallikrein do not have a bleeding disorder.
Thrombin has a large array of functions. Its primary role is the conversion of fibrinogen to fibrin, the building block of a haemostatic plug. In addition, it activates Factors VIII and V and their inhibitor protein C (in the presence of thrombomodulin), and it activates Factor XIII, which forms covalent bonds that crosslink the fibrin polymers that form from activated monomers.

2007-02-11 14:51:55 · answer #1 · answered by J.SWAMY I ఇ జ స్వామి 7 · 1 0

you can get full details of blood clotting from wikipedia

2007-02-11 14:54:47 · answer #2 · answered by anish 2 · 0 0

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