2 Hematology Flashcards
What are the initial steps of primary hemostasis?
Subendothelial collagen exposure –> Platelet adhesion–> shape change –> granulation release (ADP, TXA2) –> Recruitment –> hemostatic plug (Aggregation)
What are the three initial responses to vascular injury?
Vascular vasoconstriction
Platelet adhesion
Thrombin generation
What initiates the intrinsic pathway?
Exposed collagen
Prekallikrein
HMW kininogen
Factor XII
What are the steps in the intrinsic pathway?
Exposed collagen/prekallikrein/HMW kininogen/factor XII
- -> activates XI
- -> activate IX, then add VIII
- -> activate X, then add V
- -> convert prothrombin (Factor II) to thrombin
- -> thrombin then converts fibrinogen to fibrin
What initiates the extrinsic pathway?
Cellular injury –> release of tissue factor
Factor VII
What are the steps in the extrinsic pathway?
Cellular injury leads to release of tissue factor - reacts with VII
- -> Activates X, then add V
- -> convert prothrombin to thrombin
- -> thrombin then converts fibrinogen to fibrin
What are the steps in the common pathway?
Prothrombin (Factor II) is converted to thrombin
–> Thrombin then converts fibrinogen to fibrin
What is the prothrombin complex?
X, V, Ca, platelet factor 3 and prothrombin
Forms on platelets
Catalyzes the formation of thrombin
What is the convergence point for both coagulation pathways?
Factor X
Needed for conversion of prothrombin to thrombin
Function of Tissue factor pathway inhibitor?
Inhibits factor X
Function of Fibrin
Links platelets together
Binds GpIIb/IIIa molecule
Forms a platelet plug - hemostasis
Role of XIII
Helps crosslink fibrin
Functions of thrombin
Key to coagulation
Converts fibrinogen to fibrin and fibrin split products
Activates factors V and VIII
Activates platelets
Function of Antithrombin III
Key to anticoagulation
Binds and inhibits thrombin
Inhibits factors IX, X and XI
Heparin activates AT-III (up to 1000x normal activity)
Function of Protein C
Vitamin K-dependent
Degrades factors V and VIII
Degrades fibrinogen
Function of Protein S
Vitamin K-dependent
Protein C cofactor
What enzymes regulate fibrinolysis?
Tissue plasminoagen activator
Plasmin
Alpha-2 antiplasmin
Function of Tissue plasminogen activator
Released from endothelium
Converts plasminogen to plasmin
Function of Plasmin
Degrades factors V and VIII, fibrinogen and fibrin
Causes degradation of platelet plug
Function of Alpha-2 antiplasmin
Natural inhibitor of plasmin
Releases from endothelium
Which factor has the shortest half-life?
Factor VII
Which factors are liable - activity is lost in stored blood, but not lost in FFP?
Factors V and VIII
Which factors is NOT synthesized in the liver? Where is is synthesized?
Factor VIII
Synthesized in endothelium
Which factors are vitamin K-dependent?
II, VII, IX, X
Proteins C & S