Which element is included in the propagation phase of the in vivo coagulation model?

Which element is included in the propagation phase of the in vivo coagulation model?

• A. Activation of factor Va and factor VIIIa
• B. Feedback mechanism to thrombin
• C. Activation of platelets
• D. Final burst of thrombin

Answer: (D)

Propagation on activated platelet surfaces shifts into high gear, producing a rapid surge of thrombin. This happens as the tenase (IXa–VIIIa) and prothrombinase (Xa–Va) complexes assemble on the platelet membrane, dramatically speeding up the conversion of prothrombin to thrombin. Thrombin then amplifies the response through positive feedback, activating cofactors Va and VIIIa and promoting further platelet activation, which sustains thrombin production. The hallmark of this phase is the final burst of thrombin that drives fibrin formation and clot stabilization. Activation of Va and VIIIa and platelet activation are involved in this process, but the defining feature of propagation is the large thrombin burst.

Propagation on activated platelet surfaces shifts into high gear, producing a rapid surge of thrombin. This happens as the tenase (IXa–VIIIa) and prothrombinase (Xa–Va) complexes assemble on the platelet membrane, dramatically speeding up the conversion of prothrombin to thrombin. Thrombin then amplifies the response through positive feedback, activating cofactors Va and VIIIa and promoting further platelet activation, which sustains thrombin production. The hallmark of this phase is the final burst of thrombin that drives fibrin formation and clot stabilization. Activation of Va and VIIIa and platelet activation are involved in this process, but the defining feature of propagation is the large thrombin burst.