Schematic diagram of the blood coagulation and protein C pathways. In the blood coagulation pathway, thrombin acts to convert factor XI to XIa, VIII to VIIIa V to Va, fibrinogen to fibrin. In addition, thrombin promotes platelet activation and aggregation via activation of protease-activated receptors on the cell membrane of the platelet. Thrombin also cross over into the protein C pathway by converting protein C into APC. APC in turn converts factor V into Vi, and VIIIa into VIIIi. Finally APC activates PAR-1 and EPCR.
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