Haemostasis and its Investigation

Question 1

Outline the 3 main phases of haemostasis.

Answer 1

Primary haemostasis:

• Vasoconstriction - immediate
• Platelet adhesion - within seconds
• Platelet aggregation and contraction - minutes

Secondary haemostasis:

• Activation of coagulation factors - seconds
• Formation of fibrin - minutes

Fibrinolysis:

• Activation of fibrinolysis (minutes)
• Lysis of the plug (hours)

Question 2

How are coagulation factors and platelets separated from the blood?

Answer 2

• Coagulation factors and platelets are found in the subendothelial tissue, which contains collagen.
• These do not come into contact with blood unless there is damage to the endothelium.

Question 3

What is the role of von Willebrand factor in haemostasis?

Answer 3

• vWF stored in the endothelial cells.
• Released in response to endothelial damage.
• vWF forms a bridge between the subendothelial collagen and platelets, which are activated when they bind to vWF.