Hemostasis II Flashcards
What are 2 important intrinsic pathway proteins?
Factor XII and Factor XI
Activated on contact with negatively charged surface
Factor XII
Required for Factor XI to bind to negatively charged surface
HMKG
Binds and activates Factor IX
Factor XIa
Thrombin activation of Factor XI contributes to propagation of the
Clot
Functions in the propagation phase of clot-in conjunction with IXa
Factor XI
Associated with minor bleeding phenotype but can be clinically silent
Factor XI deficiency
Activates Factors V, VIII, IX, X, XI
Thrombin
In the intrinsic pathway, IXa forms complex with cofactor
VIIIa
This results in accelerated
Factor X to Xa formation
Xa forms complex with cofactor
Va
Xa forms complex with cofactor Va. This results in accelerated
Prothrombin to thrombin formation
The final step in the intrinsic pathway is
Thrombin cleaves fibrinogen
Activated by thrombin
Factor XIII
FXIIIa cross-links the
Fibrin chains
Extensive cross-linking increases fibrin from dimers to trimers
Tetramers
Deficiency is RARE but can cause significant bleeding
Factor XIII deficiency
An anticoagulant that regulates coagulation
Thrombomodulin
High affinity receptor for thrombin (II)
Thrombomodulin (TM)
Neutralizes thrombin’s pro-coagulantactivity
TM
Co-factor for thrombin-dependent activation of Protein C
TM
Vitamin dependent inhibitors of pro-coagulant systems
-Anticoagulants
Proteins C and S
Activated by thrombin-thrombomodulin
Proteins C and S
Factor V Activity is regulated by activated
Protein C (aPC)
Cleaves factor Va
aPC
G-to-A substitution causes Arg to Gln substitution
Factor V Leiden mutation
Factor V Leiden Mutation results in increased resistance to
Activated Protein C
Inhibits thrombin as well as factor X
Antithrombin
Short-acting drug that can only be administered parenterally
Heparin
