Coagulation/ Hemostasis

Question 1

Name 3 components hemostatic system

Answer 1

1. Circulating blood
2. Endothelium matrix
3. Sub endothelium matrix

Question 2

Morphologically describe platelet

Answer 2

Anuclear
Discoid-shaped
Subcellular fragments of megakaryocytes

Question 3

T/F The platelet plasma membrane, with its asymmetrical composition, plays a significant role in cell signaling and thrombin generation

Answer 3

True

Question 4

4 components of primary coagulation

Answer 4

1. Endothelium
2. Inner lining of blood vessels
3. Platelets
4. Extracellular matrix components of the endothelium

Question 5

What are the stages in three-stage model of platelet activation?

Answer 5

1. initiation
2. Extension
3. Stabilization

Question 6

[Primary hemostasis] Explain initiation process - 6 steps:

Answer 6

1- Exposition of subendothelial fibronectin, laminin and vWF
2- Shear stress leads to conformational changes in vWF
3- Plasma vWF is cleaved and immobilized on collagen, capture platelets at vascular lesions
4- VWF and platelet glycoprotein results in tethering and rolling of platelets along the endothelium
5- As velocity of rolling decreases, bonds between vWF and glycoprotein increases and strengthen
6- Finally this leads to adhesion and formation platelet monolayer

Question 7

[Primary hemostasis] Explain extension process - 5 steps:

Answer 7

1- Formation of procoagulant membrane
2- Integrin activation
3- Local accumulation of thrombin
4- Secretion of thromboxane A2 and ADP: activation of nearby platelets
5- initiate platelet aggregation facilitated by conformational changes

Question 8

[Primary hemostasis] Explain Stabilization process- 3 steps:

Answer 8

1. Firm adhesion to fibrinogen via platelet integrins leading to clustering
2. Actin/myosin filament strengthen the plt-to-plt interaction narrowing the gap between platelets
3. Clot contraction caused by fibrin deposition

Question 9

What is the end goal of secondary hemostasis?

Answer 9

Stable fibrin clot

Question 10

[Cell-based model of coagulation] Summary of the main events of initiation

Answer 10

1. TF (tissue factor) come into contact with FVIIa
2. FVIIa facilitates formation of small amount of thrombin (FIIa)

Question 11

[Cell-based model of coagulation] Summary of the main events of amplification

Answer 11

1. Thrombin (FIIa) activates platlets to degranulate and externalize phosphatidylserine
2. Facilitates their adhesion to subendothelial matrixes
3. Activates factors V, VIII, XI

Question 12

[Cell-based model of coagulation] Summary of the main events of propagation

Answer 12

1. Formation of tenase (FIXa - FVIIIa)
2. Formation of prrothrombinase complex (FXa - FVa)
3. Massive formation of thrombin

Question 13

[Cell-based model of coagulation] Summary of the main events of termination

Answer 13

1. Endogenous anticoagulants counters thrombin generation
   
   • Tissue factor pathway inhibitor (TFPI)
   • Protein C (PC)
   • Protein S (PS)
   • Antithrombin

Question 14

What are the primary initiators of fibrinolysis?

Answer 14

Tissue plasminogen activator (tPA) and urinary type plasminogen activator

Question 15

Which is the most important inhibitor of fibrinolysis?

Answer 15

PAI-1 (plasminogen activator inhibitor 1)

Question 16

Factors present in intrinsic pathway

Answer 16

XII, XI, IX, VIII

Question 17

Factors present in extrinsic pathway

Answer 17

VIIa, Tissue Factor

Question 18

Factors present in common pathway

Answer 18

X, V, prothrombin (II), fibrinogen (I), XIII