Coagulation Flashcards
(21 cards)
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
proteins c and s
s is cofactor for c (activated by thrombomodulin-thrombin) to inactivate V and VIII
protein z
inhibits Xa
thrombomodulin
binds thrombin to inactivate it. this activates protein c/s system
tPA
produced by endothelial cells. plasminogen to plasmin.
plasmin
protease that leads to fibrin degradation, releases D dimers
suppressors of fibrinolysis
PAI-1 (plasminogen activator inhibitor), alpha 2 antiplasmin and microglobulin, TAFI (thrombin activatable fibrinolysis inhibitor)
