Anticoagulants & Procoagulants

Question 1

What are the 3 phases of the new coagulation model?

Answer 1

Initiation Phase
Amplification Phase
Propagation Phase

Question 2

Which older model pathway does the initiation phase (I) of the new coagulation model reflect?

Answer 2

Extrinsic pathway

Question 3

Which older model pathway does the amplification phase (II) of the new coagulation model reflect?

Answer 3

Intrinsic pathway

Question 4

Describe the initiation phase of the new coagulation model.

Answer 4

Phase I: Vessel damage leads to release of tissue factor release which binds with VIIa which converts X to Xa, releasing a SMALL amount of thrombin.

Question 5

Describe the amplification phase of the new coagulation model.

Answer 5

Phase II: Platelets, V, & XI are activated by thrombin

Question 6

Describe the propagation phase of the new coagulation model.

Answer 6

Phase III: VIII, IX, and calcium on platelets activate X while thrombin activates platelets, V, VIII, creating a VIIIa-IXa complex.
The VIIIa-IXa complex switches the reaction to the intrinsic Xase pathway, which is 50 TIMES more efficient at Xa generation. This leads to a LARGE amount of thrombin production.