Coagulation Flashcards
why is the extrinsic pathway insufficient to cause clotting
because it is rapidly inactivated by tissue factor pathway inhibitor (TFPI)
describe fibrinogen structure
alpha, beta, gamma peptide chains. A and B are capped in the central area. Thrombin removes caps allowing binding by other fibrin molecules
what factors need vit K
2,7,9,10,c,s,z. Vit. K is a coenzyme which gamma-carboxylates glutamic acids on these proteins so they can interact w/ phosphotidylserine
VKORC1
reduces Vit K to active form, inhibited by warfarin
deficiency in FXI
mild bleeding b/c FIX is also activated by TF-VIIa
FXII,preKalikrein and HMWKininogen deficiency
prolonged aPTT but no bleeding b/c FXI is also activated by thrombin
at what point do you get PT/aPTT prolongation
when factor activities drop below 30-40%
PT
VII and X,V,II,I. Add TF and Ca++ to citrated plasma. Fibrin formation in ~10-15 sec.
aPTT
XII,XI,IX,VIII,HMWK,PK and common. add phospholipid(akaThromboplastin), surface activator and Ca++ to citrated plasma. Fibrin forms in ~30-40 sec.
where are factors sythesized
liver, FVIII also peripherally
which factor has the shortest T1/2 and what is it
VII, 4-6 hrs
Thrombin time
fibrinogen->fibrin. Thrombin added to platelet-poor plasma. Prolongation due to hypofibrinogenemia and dysfibrinogenemia
Platelet aggregation inhibitors secreted by intact endothel
NO, prostacyclin (PGI2), CD39
ADAMTS13
cleaves vWF
Antithrombin
forms complex w/ heparin and thrombin which inactivates thrombin and Xa
