An Introduction to the Fundamentals of Coagulation: Overview of Secondary Hemostasis

Secondary Hemostasis – The Extrinsic Pathway

  • Functional control of the extrinsic pathway is mediated by Tissue Factor Pathway Inhibitor (TFPI) which binds to and inhibits factor X.
  • Remember, for hemostatic processes to continue, factor VIIa must be able to promote the chemical conversion of factor X into factor Xa. TFPI effectively blocks this action, thereby controlling the initiation of the common pathway.
  • The Prothrombin time (PT) is used to monitor the extrinsic pathway, and the activity of oral anticoagulants such as Coumarin.

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