Haematology 3 - Coagulation Flashcards
Recall 4 endogenous anti-coagulants
Anti-thrombin
TFPI
Protein C
Protein S
Recalll 3 procoagulant factors and 1 anticoagulant factor that are synthesised in vascular endothelium
PGI2
vWF
Plasminogen activators
Thrombomodulin
Recall the 2 possible mechanisms of platelet activation
- vWF binds to Gp1b which binds to platelets to activate them
- Endothelial Gp1a binds directly to the platelet to activate
Via which receptors to platelets adhere to each other, and what is needed for this to happen?
GpIIb/IIIa using fibrinogen and calcium
Recall one inducer and one inhibitor of platelet aggregation, and the enzyme required for the synthesis of both
Thromboxane A2 increases aggregation
PGI2 inhibits platelet aggregation
COX enzyme
Why does aspirin have an anticoagulant effect?
Inhibits COX enzyme which is necessary for thromboxane A2 production
What is the rate-limiting step in fibrin formation?
Factor Xa
Which clotting factors are vitamin K dependent?
II, VII, IX and X
How does vitamin K activate clotting factors?
Via gamma decarboxylation
Recall 4 factors that promote fibrinolysis
Factor IXa, Xa, TPA and urokinase
These all increase plasmin production which cleaves fibrin
What is the role of plasmin?
Breaks down fibrin in fibriolysis
What is the mechanism of action of heparin?
Augments anti-thrombin effect
What is the role of proteins C and S?
Inactivate Factors 5 and 8
What are the roles of tissue factor and TFPI
Tissue factor activates factor Xa
TFPI neutralises tissue factor
How can platelet and coagulation factor disorders be distinguisghed clinically?
Platelet problems –> immediate superficial bleeding
Coagulation factor deficiencies –> delayed, deep bleeding and haemarthroses