Secondary Hemostasis Flashcards
What is secondary hemostasis?
Stabilization of the platelet plug via fibrin meshwork.
Where are coagulation factors synthesized?
In the liver
What is the “common pathway” in the coagulation cascade? (3 steps)
X to Xa
Xa converts Prothrombin (II) to Thrombin
Thrombin converts Fibrinogen to Fibrin
What coagulation factors activate X?
IXa (from the Intrinsic Pathway)
VII (from the Extrinsic Pathway)
What is the “intrinsic pathway” in the coagulation cascade? (4 steps)
Inflammatory mediators cause conversion of XII to XIIa
XIIa converts XI to XIa
XIa converts IX to IXa
IXa converts X to Xa
What is the “extrinsic pathway” in the coagulation cascade? (2 steps)
Tissue factor (III) converts VII to VIIa VIIa converts X to Xa
What is required for the initiation of secondary hemostasis?
Tissue factor
What are the Vitamin K dependent cofactors? (4 things)
II
VII
IX
X
What happens in the cycle of vitamin K? (5 steps)
Proenzymes are carboxylated
Vitamin K is converted to an epoxide in the process
Epoxide is reduced to Vitamin K
Vitamin K is reduced (activated)
Vitamin K-dependent carboxylase carboxylates Proenzymes
What is a key factor that promotes amplification of secondary hemostasis?
Thrombin
What 4 factors does Thrombin affect during amplification?
XI
VIIIa
VII
Va
Which coagulation factor has the shortest half-life?
7
What cofactor is required for antithrombin to inactivate thrombin?
Heparin
What does antithrombin inhibit? (3 things)
Thrombin
IXa
Xa
How does antithrombin work? ( 3 steps)
- Heparin binds to antithrombin to cause a conformational change and reveal an thrombin binding site.
- Thrombin binds to antithrombin
- The TAT complex is phagocytozed
