Hemostasis and Thrombosis

Question 1

What is hemostasis?

Answer 1

Process initiated to arrest hemorrhage by forming a blood clot in response to vascular injury.

Question 2

What is thrombosis?

Answer 2

Pathologic process leading to formation of a blood clot (thrombus) within the circulation

Question 3

What is the general cause of thrombus formation? What for processes contribute?

Answer 3

Antithrombotic systems fail to balance prothrombotic processes

1. Activation of platelets
2. Activation of coag pathways
3. Participation of monocyte/macrophage system
4. Active involvement of the endothelial cells of the vessel walls

Question 4

What is the endpoint goal of the coagulation cascade?

Answer 4

Conversion of fibrinogen to the fibrin polymer via the serine protease enzyme, “thrombin”

Question 5

What is tissue factor and what is its role in the coagulation cascade? What inhibits it?

Answer 5

TF associates with Factor VIIa forming the TF:VIIa complex. TF:VIIa activates factors X and IX; TFPI inhibits the TF:VIIa complex

Question 6

Describe the coagulation cascade. In the presence of what does Xa bind to Va? What complex does it form and what is the job of the complex?

Answer 6

Calcium; Prothrombinase Complex which promotes activation of prothrombin to thrombin

Question 7

What anticoagulative properties does thrombin have?

Answer 7

• Produce fibrinolytic molecules
• Regulation of GFs
• Regulation of WBC adhesion molecules
• Mediates Protein C anticoag pathway

Question 8

What angticoagulant properties does V have?

Answer 8

Modulates protein C system which downregulates VIIIa

Question 9

Describe platelet actions in vascular injury

Answer 9

• Gp Ib (platelet protein) binds to vWF
• Platelets recruit other platelets thru ADP and TXA2
• Platelets bind to each other thru GpIIb/IIIa -fibrinogen-GpIIb/IIIa binding

Question 10

What are the functions of NO and Prostacyclin (PGI2) in the coagulation cascade?

Answer 10

• NO - inhibits platelet agg and adhesion to vessels
• PGI2 - inhibits platelet agg

Question 11

What activates antithrombin? What is the mechanism of antithrombin?

Answer 11

Endothelial heparan sulfate; Binds IIa, IXa, Xa, Xia, and XIIa

Question 12

By what means does thrombin help to terminate the coagulation cascade?

Answer 12

Thrombin attaches to thrombomodulin (receptor on endothelial cells). Thrombomodulin then activates Protein C which destroys V and VIII

Question 13

What are the three general major causes of thrombus formation?

Answer 13

1. Endothelial continuity is lost
2. Endothelial function is altered
3. Blood flow in a vessel becomes abnormal

Question 14

What is the most common denuding injury to the endothelium?

Answer 14

Atherosclerotic plauqes

Question 15

What are the 4 fates of a thrombus?

Answer 15

1. Lysis
2. Growth and Propagation
3. Embolization
4. Organization and Canalization

Question 16

Describe the mechanisms of fibrinolysis

Answer 16

Question 17

Describe the process of recanalization

Answer 17

Remodeling of a thrombus in which fibroblasts enter the thrombotic meshwork and digest fibrin to form a fibrous structure with its own new blood vessels