What role does tissue factor play in coagulation?

Tissue factor, also known as thromboplastin or CD142, plays a crucial role in the coagulation process by initiating the extrinsic pathway of coagulation. This pathway is one of the two main coagulation cascades, the other being the intrinsic pathway. When there is vascular injury, tissue factor is exposed to the circulating blood and binds to factor VII, which is then activated to factor VIIa.

This complex of tissue factor and activated factor VII subsequently activates factors IX and X in the coagulation cascade, leading to the generation of thrombin. Thrombin is essential for converting fibrinogen to fibrin, which forms the structural basis for a blood clot.

Understanding the importance of tissue factor highlights its role in the quick response to injury, enabling the body to stem bleeding rapidly through the extrinsic pathway. This pathway is significantly faster than the intrinsic pathway, underscoring tissue factor's critical function in hemostasis.