HAEM: Coagulation I - Bleeding Disorders

Question 1

• Fill in the diagram with the relevant substances.
• If the right side of the swing goes up i.e. increased clot lysis and decreased clot formation, what sort of disorders form?

Answer 1

Bleeding disorders.

Question 2

Describe (broadly) the four stages of vascular endothelial damage.

• What initiates the process of haemostasis?
• When does the coagulation cascade start? What does it do?

Answer 2

1. Vascular endothelial damage → gap in the wall of the blood vessel.
2. Platelets activated → unstable platelet plug formed.
3. Coagulation cascade → formation of fibrin, which cross-links and stabilises the platelet plug.
4. Plasminogen develops into plasmin, which produces degradation products, to lyse the clot.

Question 3

• What two chemicals are produced when endothelium is intact to prevent platelet adherence?
• Injury impairs these processes and exposes subendothelial elements. What are these three elements?

Answer 3

• Nitric oxide and prostacyclin.
• Microfibrils, laminin and collagen.
  
  • Platelets bind to subendothelial collagen to initiate primary closure of the vessel wall defect