PATH: Hemostasis and Thrombosis

Question 1

What is the function of hemostasis?

Answer 1

To maintain blood in the vascular system fluid and free of clots , yet allow rapid activation of clotting if necessary

Question 2

What is thrombosis?

Answer 2

A pathologic extension of hemostasis in which there is inappropriate activation of the hemostatic system

Question 3

What are the anti-thrombotic properties of endothelium?

Answer 3

Anti-platelet effects (barrier function, ADP breakdown, NO, prostacyclin), anti-coagulant properties, and fibrinolytic properties (t-PA)

Question 4

What are the pro-thrombotic properties of endothelium?

Answer 4

Synthesis of von Willebrand Factor, procoagulant (synthesize tissue fator activating extrinsic coag. pathway, and expresses binding sites for activated clotting factors IX and X), and anti-fibrolytic (PAI)

Question 5

What kind of granules do platelets contain?

Answer 5

Alpha granules and electron dense bodies

Question 6

What are 3 functions of activated platelets in hemostasis?

Answer 6

Adhesion to ECM (vWF), secretion/ release, aggreagation causing generation of ADP, thrombin and TXA2

Question 7

What occurs during primary hemostasis?

Answer 7

Vasoconstriction, exposure of blood elements to collagen, release of tissue factors that activate coagulation cascade and formation of a hemostatic plug at the SOI

Question 8

What is the effect of TXA2?

Answer 8

Causes vasoconstriction which lowers blood flow to the area allowing more platelets to filter out and become attracted to other platelets. This allows for the formation of the primary hemostatic plug

Question 9

How do platelets bind to vWF?

Answer 9

Gp1b receptors

Question 10

How are platelets bound to one another in a hemostatic plug?

Answer 10

Connected through fibrinogen

Question 11

What converts Fibrinogen to fibrin and what effect does this have?

Answer 11

Thrombin converts fibrinogen to fibrin which is a much stronger molecule

Question 12

What are the effects of thrombin in generating hemostasis?

Answer 12

Increase neutrophil adhesion, activate monocytes, lymphocytes, and endothelium, converts fibrinogen to fibrin and increases platelet aggregation and stimulation which causes thromboxane A2 release

Question 13

What are the initiators of the intrinsic and extrinsic coagulation pathways?

Answer 13

Extrinsic by tissue factor and intrinsic by Factor XII or Hageman Factor

Question 14

What is the ultimate goal of the coagulation pathways?

Answer 14

Activation of Factor II to IIa (thrombin)

Question 15

What products are released by the endothelium that block the coagulation cascade?

Answer 15

Thrombomodulin and t-PA

Question 16

How does plasmin act?

Answer 16

Acts on fibrin to make fibrin degradation products

Question 17

What is a thrombus?

Answer 17

A solid mass or plug formed from blood elements found at the site of formation

Question 18

What is an embolus?

Answer 18

Detached intravascular solid, liquid, or gaseous mass found at a site different from its origin

Question 19

What is Virchow’s Triad?

Answer 19

The three major factors that favor thrombosis: vascular lesions (endothelial injury), decreased flow (stasis), and hypercoagulability

Question 20

What is the cellular driver and mediator of arterial thrombosis? Venous? Which is more common?

Answer 20

Arterial- platelet driven/mediated; Venous- RBC; Arterial more common

Question 21

What is activated protein C resistance?

Answer 21

Factor V deficiency where heterozygotes are 3-10 times more likely to develop thromboses, and homozygotes have a 50 fold increased risk

Question 22

What are the possible fates of a thrombus?

Answer 22

Propagation, Embolization, Dissolution, or Organization (recanalization)