In the cell-based model of coagulation, initiation and amplification is driven by which surface?

In the cell-based model of coagulation, initiation and amplification is driven by which surface?

• A. Activated platelet surface
• B. Tissue factor bearing cell
• C. Proteolytic digestion of fibrinogen
• D. Activation of the contact pathway

Answer: (B)

In the cell-based model, the trigger starts on a tissue factor–bearing cell. When tissue factor (on nonvascular cells) binds factor VIIa, the TF-VIIa complex on that surface activates factor X to Xa and factor IX to IXa, producing a small initial burst of thrombin. That thrombin then activates platelets and cofactors, setting up the amplification/propagation phase on the activated platelet surface where large amounts of thrombin are generated and fibrin is formed. So the surface driving the initiation and providing the cue for amplification is the tissue factor–bearing cell. The activated platelet surface is where amplification actually builds, but initiation depends on TF-bearing cells.

In the cell-based model, the trigger starts on a tissue factor–bearing cell. When tissue factor (on nonvascular cells) binds factor VIIa, the TF-VIIa complex on that surface activates factor X to Xa and factor IX to IXa, producing a small initial burst of thrombin. That thrombin then activates platelets and cofactors, setting up the amplification/propagation phase on the activated platelet surface where large amounts of thrombin are generated and fibrin is formed. So the surface driving the initiation and providing the cue for amplification is the tissue factor–bearing cell. The activated platelet surface is where amplification actually builds, but initiation depends on TF-bearing cells.