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USMLE
Coagulation
Question | Answer |
---|---|
What is found in the alpha granules of platelets? | Fibrinogen Fibrinectin VWF Thrombospondin Vitronectin |
What is found in the dense bodies? | ADP ATP 5HT Ca |
Steps of primary hemostasis | Injured BV has exposed collagen VWF binds collagen GPIb of platelet binds to VWF, causing conformational change in IIb/IIIA IIb/IIIA is now able to bind fibrinogen Platelets express receptors for factors V and VIII; extend pseudopods |
What role does TXA2 play in coagulation and how does it work? | TXA2 causes platelet aggregation and vasocontriction. It decreases the level of cAMP, which causes an increase in Ca, which promotes platelet aggregation. |
How does PGI2 work in coagulation? Where does it come from? | Opposes the action of TXA2 by increasing the levels of cAMP, which decreases the levels of Ca. This inhibits platelet aggregation. It is released by vascular endothelial cells. |
What role does ADP play in coagulation? | Causes platelets to swell and adhere to each other. It then caauses them to release TXA2 and more ADP in a positive feedback mechanism. The clot formed is large enough to fill the injured area. |
What is the tenase reaction? | The reaction that causes the formation of Xa (IXa + VIIIa + X) -> Xa |
What does factor XIII do? | Provides clot strength and normal wound healing. Without it, clots dissolve more quickly |
What does ATIII bind to? | Heparan sulfate |
What does AT III inactivate? | IX, X, XI, II |
What do proteins C and S inactivate? | Va, VIIIa |
What does TFPI do? | Inactivates VIIa-TF complexes |
What does heparin do? | Enhances the activity of ATIII (inactivates Ix, X, XI, II) |
What does warfarin do? | Binds vitamin K, so II, VII, X, XI, protein C and S are all inhibited |
What does thrombomodulin do? | Causes the activation of protein C Also inactivates all the other serine proteases in coagulation |
What does tPA do? | Converts plasmingen to plasmin, which then breaks up the clot and releases FSP (D-dimer) |
What does urokinase do? | converts plasminogen -> plasmin, forms FSP (d-dimer) |
What releases tPA and urokinase? | Endothelium Fibrin |
What does PAI-I do? | down-regulates plasmin |
What is alpha-2-anti-plasmin? | Inhibits fibrinolysis, by collecting free plasmin |
IL-11 | Allows for increasing the number of circulating platelets |
C-MPL | TPO receptor on platelets |
Treatments for VWD | DDAVP Intermediate Purity Factor |
What is Intermediate Purity Factor | Combination of VWF and factor VIII; used to treat VWD |