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Blood and Lymph Section III > Hemostasis > Flashcards

Flashcards in Hemostasis Deck (10)
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1

What are the four steps of primary hemostasis?

Injury, Adhesion, Activation, and Aggregation

2

What occurs during the first step of primary hemostasis, injury?

von Willebrand Factor binds to exposed collagen upon endothelial damage.

3

What occurs during the second step of primary hemostasis, adhesion?

Platelets bind vWF via GpIb receptor at the site of injury only. Platelets release ADP and Ca2+ which are necessary for coagulation cascade. ADP helps platelets adhere to endothelium.

4

What occurs during the third step of primary hemostasis, activation?

ADP binding to receptor induces GpIIb/IIIa expression at platelet surface.

5

What occurs during the fourth step of primary hemostasis, aggregation?

Fibrinogen binds GpIIb/IIIa receptors and cross-links platelets. Balance of pro- and anti-coagulation factors begins: Platelets produce TXA2, procoag factor decreases blood flow and increases platelet aggregation; Endothelial cells release PGI2 and NO, anti-coag factors that increase blood flow and decrease platelet aggregation.

6

What factors does Vitamin K help produce and how does warfarin counter its activity?

II, VII, IX, X, Protein C, Protein S. Only reduced Vitamin K can carry out its function. Warfarin inhibits epoxide reductase enzyme from reducing Vitamin K, producing a Vit K shortage.

7

What is the activation process and activity of Protein C?

Protein C + Thrombin/Thrombomodulin complex = Activated Protein C (APC); APC + Protein S = cleavage and inactivation of Factors Va and VIIIa.

8

What is the activation process and activity of Plasminogen?

Plasminogen + tPA = Plasmin; Plasmin = Fibrinolysis, cleavage of fibrin mesh, destruction of coagulation factors.

9

What action does Ticlopidine and clopidogrel have on thrombogenesis?

Ticlopidine and clopidogrel irreversibly block the ADP receptor on platelet surface membranes, inhibiting the expression of GpIIb/IIIa, and thus inhibiting cross linking of platelets.

10

What is the method of action of Abciximab?

Abciximab directly inhibits GpIIb/IIIa on the platelet surface.