Haemostasis Basics

Question 1

3 stages of coagulation

Answer 1

1. Initiation: following vascular insult. Initial Thrombin production
2. Propagation: Thrombin burst
3. Stabilisation: Fibrin production + degradation

Question 2

2 types of haemostasis and the types of bleeding caused by disorders in each

Answer 2

Primary: platelet adhesion + aggregation. Superficial bleeding
Secondary: coagulation cascade
Deep bleeding

Question 3

Describe initiation

Answer 3

Tissue factor + FVIIa join
TF/FVIIa complex activate FIX
FIXa activates FVIII
FVIIIa activates FX
FXa then joins FVa to activate prothrombin (II) to thrombin (IIa)

Question 4

Describe propagation

Answer 4

Thrombin activates:
FVIII to FVIIIa
FV to FVa
FIX to FIXa
By having more co-factors, more Thrombin will be produced

Question 5

Describe clot stabilisation

Answer 5

Thrombin activates fibrinogen to form fibrin
Fibrin gets cross-linked with FVIIIa: stable clot

Question 6

3 regulators of coagulation cascade

Answer 6

Tissue Factor Pathway Inhibitor
Antithrombin
Activated Protein C

Question 7

What does Tissue factor pathway inhibitor do?

Answer 7

Stops FVII from becoming FVIIa
Prevents initiation

Question 8

What does antithrombin do?

Answer 8

Inhibits Thrombin
+ Inhibits activation of FX (further preventing Thrombin being formed)
Inhibits propagation

Question 9

What does activated Protein C do?

Answer 9

Inhibits activation of FV + FVIII (preventing thrombin forming)
Inhibits propagation

Question 10

Inheritance of vW disease

Answer 10

AD: Quantitative
AD: Qualitative
AR: Quantitative + Qualitative

Question 11

Describe primary haemostasis

Answer 11

Endothelial cell anti-coagulant
Subendothelium ECM pro-coagulant
Damage
vWF rushes into subendothelial space + binds ECM, VSMC + TF
Platelets bind to vWF + activate + aggregate