Factor that oppose clot formation (Anticoagulants)

there are at least three different mechanism that oppose clot formation thereby helping to limit this process and prevent it form spreading excessively.

(a) The first anticoagulation mechanism acts during the initiation phase of clotting. it utilizes the plasma protein called tissue factor pathways inhibitors (TFPI),secreted mainly by endothelial cells (TEPI) binds to the tissue factor factor VIIa complex and inhibits the generation of factors X

(b) The second anticoagulant mechanism is triggered by thrombin, which binds to the endothelial cell receptor ,thrombomodulin. this binding eliminates all of thrombin's clot producing effect and activation plasma protein C this protein in combination with another plasma protein inactivates factor VIIa and Va