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Fibrin Formation and Regulation of Hemostasis: Learning Objectives

Medical Importance

Controlled activation of the coagulation system is essential to keep us from bleeding to death from minor trauma. Understanding this pathway is crucial in order to understand defects in coagulation such as hemophilia, how the various coagulation tests work, and the action of antithrombotic agents.

Since blood coagulation is a potentially explosive process that could, in the absence of precise regulation, quickly lead to massive thrombosis and death, the body has several mechanisms to limit thrombus formation to areas of injury, and to prevent extension into normal blood vessels.


  1. Know the pathways for blood coagulation (the intrinsic, extrinsic, and common pathways) that lead to the formation of fibrin.
  2. Know what events trigger coagulation.
  3. Be able to identify which coagulation factors are dependent on vitamin K and how vitamin K modifies these coagulation factors.
  4. State the crucial role of the cofactors V and VIII in coagulation.
  5. Know how fibrinogen is converted into fibrin.
  6. Know what Factor XIII does.
  7. Be able to name key enzymes of fibrinolysis and inhibitors of fibrinolysis.
  8. Be able to briefly discuss the mechanism of activation of the fibrinolytic system at the site of vascular injury with an overlying thrombus.
  9. Be able to explain (or diagram) how activated protein C and antithrombin act as inhibitors of coagulation.