MEDizzy - In an experiment, thrombus formation is studied in areas of

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Hemodynamic Disorders

In an experiment, thrombus formation is studied in areas of vascular damage. The propagation of a thrombus in an area of vascular injury to adjacent normal arteries is prevented. Which of the following substances diminishes thrombus propagation by activating protein C?

ExplanationThrombomodulin is present on intact endothelium and binds thrombin, which then inhibits coagulation by activating protein C. Normally, thrombin activates factors V, VIII, and IX, and also stabilizes the secondary hemostatic plug by activating factor XIII, which cross-links fibrin. Thrombin helps activate platelets. Calcium is a cofactor that assists clotting in the coagulation cascade (ethylenediaminetetraacetic acid [EDTA] in some blood collection tubes binds calcium to prevent clotting). Fibrin protein forms a meshwork that is essential to thrombus formation. Platelet factor 4 is released from the α granules of platelets and promotes platelet aggregation during the coagulation process.