280b hemostasis Flashcards Preview

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Flashcards in 280b hemostasis Deck (10):
1

1st step in hemostasis following vessel injury?

neural vasoconstriction

2

what doe endothelial cell release following injury? what is in it?

Weibel-palade bodies

endothelin - vasoconstriction
selectins - rolling of platelets and WBCs
vWF - binds GpIb on platelets

3

what do WBCs release after they start rolling on endothelium due to selectins?

microparticles put tissue factor on surface --> bind platelets and activate

4

how are the extrinsic and intrinsic pathways connected?

TF-VIIIa activate intrinsic

extrinsic (TF-VIIa and Xa) --> small amount of X --> small amount of thrombin --> activates intrinsic pathway

intrinsic is required to form clot b/c extrensic only gets the process started

5

where does coagulation cascade occur?

surface of cells - WBCs rolling along have TF; platelets have other factors on surface

6

test for clotting? what is added? what is test tubes and blood bags to stop clotting?

intrinsic - PTT (partial thromboplastin time) - add silicates/PL

extrinsic - PT (prothrombin time) - add TF

citrate binds Ca

7

vitamin K - fxn

reduced form (vit K epoxide I-- warfarin) --> coenzyme for g-carboxylation of II, VII, IX, X, C, S, Z

allows Ca bridge to form b/w negative membrane PL (phosphatidylserine on platelets and macrophages)

8

Fibrin and FXIII

fibrinogen - triple helix of peptides -- dimer with disulfide bonded

thrombin cuts off fibrinopeptides A and B --> leave knobs that allow proper fitting b/w dimers to form a half-staggered sequence --> long aggregated polymer

cross linking via FXIII --> forms bond b/w dimers, activated by thrombin

9

limiting factors for blood coagulation?

prothrombin

F V

F VIII

Ca --> must give with blood transfusions b/c citrate is in bad which blocks Ca action --> too low of Ca to form clot

Fibrinogen

10

what does intact endothelium releases that inhibits platelet aggregation? cleaves vWF? binds thrombin?

NO
PGI2
CD66 (ectoADPase)

ADAMSt13 --> vWF

Thrombomodulin --> binds thrombin