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

Secondary Hemostasis – The Extrinsic Pathway

  • The shortest, and least complex of the three pathways, the extrinsic pathway primarily focuses on the interaction of tissue factor with factor VII, leading to the activation of factor VII.
  • Tissue factor, a substance expressed on the surface of cells such as fibroblasts and macrophages found outside the vasculature, initiates coagulation when plasma contained within the vessel walls leaks outside the broken vessel, and comes into contact with these cells.
  • The nomenclature, extrinsic pathway, comes from the fact that tissue factor is external to the vasculature.

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