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Blood coagulation & Thrombus Formation


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What is consolidation?
The retraction of the hemostatic plug by active shortening of platelet contractile filaments.
What enzyme is responsible for fibrinolysis?
Plasmin, a protease formed from the proenzyme plasminogen
What is the role of Factor XIIIa and how is it activated?
Factor XIIIa is responsible for the formation of covalent crosslinks in fibrin; it is activated by thrombin.
What are the substrates for platelet adhesion?
Collagen and Von willebrand Factor (VWF).
What substances does the endothelium release to inhibit clot formation?
Prostacyclin (PGI2) and NO2.
Where is tissue factor found?
Tissue factor (TF) is found on most non-vascular cells and can be found on endothelial cells after being activated.
How is thrombin generated initially?
By a complex of Factor Xa and Factor V on the membrane of tissue factor-bearing cells. Complex formation markedly accelerates the rxn.
How does ADP affect coagulation?
ADP is an activator
How do platelets aggregate?
By means of fibrinogen molecules binding to fibrinogen receptors which are exposed only on activated platelets.
what is the role of the TFPI-Xa complex?
It inhibits VIIa, which increases the importance of the intrinsic pathway as thrombin generation proceeds.
What is the role of the VIIa-TF complex?
It is the main activator of Factor IX and Factor X.
What is meant by the thrombin burst?
The cascade happens faster on the platelet surface faster than anywhere else.
What deficiency causes classic Hemophilia?
Factor VIII
Which factor is not required for hemostasis?
Factor XII
How is blood anticoagulated for PT or APTT?
by chelating Calcium with citrate
Which factors are Vitamin K dependent?
What is Vitamin K's role?
It catalyzes the addition of an extra carboxyl group to certain glutamic acid residues in each of the vitamin K-dependent factors, converting them to gamma-carboxyglutamic acid.
Where in the coagulation cascade does Warfarin act?
Warfarin inhibits the conversion of glutamic residues on the vitamin K dependent factors to gamma-carboxyglutamic acid.
How is a PT done?
Add the reagent tissue factor and Ca and time the process
How is APTT done?
Add the activator and phospholipid and incubate. Then ad Ca later.
What is the difference between PT and APTT?
PT only mesures the integrity of the extrinsic pathway while the APTT measures the integrity of both extrinsic and intrinsic.
What is the most important inhibitor of thrombin activity?
What is heparin's relationship to anithrombin?
The rate of thrombin inhibition is much enhanced when antithrombin binds to certain negatively charged polysaccharides including warfarin.
What is the role of Thrombomodulin and Modulin (complex)?
together they activate the proenzyme Protein C
What is the role of Protein Ca?
Protein Ca catalyzes the proteolytic inactivation of Factors V and VIII when complexed with Protein S.
What is the most common of the "thrombophilias?"
Activated Protein C (APC) resistance is the most common

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