<prompt> Which of the following is a procoagulation protein ?ThrombomodulinProtein CProtein SThrombin  <response>: Ans. is d i.e., Thrombin Coagulation Cascade o Coagulation cascade is a series of enzymatic conversions, turning inactive proenzymes into activated enzymes and culminating the formation of thrombin. o Thrombin then conves the soluble protein fibrinogen precursor into insoluble fibrous protein fibrin. o The blood coagulation pathway are divided into. 1.Extrinsic -- Activated by tissue factor. 2.Intrinsic -- Activated by factor XII Hagmen factor. o In vivo coagulation is predominantly occurs extrinsic pathway. o Clotting is regulated by three types of natural anticoagulants. Antithrombin III -- Binds to heparin like molecule on endothelial surface and this complex inhibit factor II thrombin, IX, X, XI, XIL Protein C S -- These are Vit K dependent proteins. Thrombomodulin bind to thrombin and this complex activates protein C, which then, with the help of protein S as a cofactor, inactivates factor V VIII. Tissue factor pathway -- Secreted by endothelium and inactivates tissue factor VII factor X. inhibitor TFPI 