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?
- V, VII, IX, X
- 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?
- Antithrombin
- 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