Haemostasis + thrombosis Flashcards
What are the 2 stages of haemostasis?
- Primary → formation of the primary platelet plug
* Secondary →formation of insoluble, cross-linked fibrin
What is the first step in primary haemostasis?
Vasoconstriction
What causes vasoconstriction post trauma to the endothelium of a blood vessel?
- Smooth muscle contraction
* Release of endothelin → causes vasoconstriction
If endothelin constricts the smooth muscle of vessels, what 2 agents dilate smooth muscle in vessel walls?
- Nitric oxide
* prostacyclin
What is the second step of primary homeostasis?
Platelet adhesion
vWF
What are the 2 main glycoprotein receptors on the platelet surface?
- GlycoProtein 1b
* GlycoProtein 2b/3a
What does von Willebrand factor do?
- primary function is binding to other proteins
- Particular strong binding to factor VIII
- It is important in PLATELET ADHESION to the wound.
•It binds to collagen in the wound and GP1b on the platelet.
When do platelets degranulate and change shape?
- Once they have been bound by vWF
* once they are activated and both degranulate and change shape.
What do platelet Alpha granules contain?
- Fibrinogen
* von wilebrand factor
What do platelet dense granules contain?
Serotonin → constricts smooth muscle cells
ADP → activates platelets and promotes aggregation
Ca++ → Needed for secondary haemostasis
SAC
what are the 2 granules inside platelets called?
- alpha granules
* dense granules
what does the gp2/3a receptor do?
It binds fibrinogen
what does the GP1a receptor do?
It binds to vWF
What happens in the second phase of haemostasis?
Fibrin aggregates over the clot.
What is haemophilia A
Clotting Factor 8 deficiency
What is Haemophilia B
Clotting factor 9 deficiency
Where is fibrinogen sythesized?
In the liver
what is the extrinsic pathway?
- Tissue damage releases tissue factor,
- this and factor 7 activate factor 10 → 10a
- which then cleaves prothrombrin → thrombrin
What is the intrinsic pathway?
- 11 →11a
- 11a activates 9 →9a
- 9a activates 8 →8a
- 8a activates 10
What is responsible for haemolysis?
Plasmin
What is cleaved to become plasmin?
plasminogen
What happens when fibrin is degraded?
It is picked up by macrophages that recycle the component parts in the spleen and the liver.
What are the 5 tests for clotting?
- Clotting time
- Prothrombrin time → extrinsic pathway
- thrombrin time
- APTT activated partial prothrombrin time →intrinsic pathway
- fibrinogen concentration
Coagulation failure is linked to which pathway?
The intrinsic pathway
Primary homeostatic failure is linked to which pathway?
The extrinsic pathway
What are the symptoms of primary homeostatic failure?
- Immediate bleeding
- mucocutaneous bleeding → mouth/gut
- Purpura