Lecture 19 - Blood coagulation Flashcards
What are the components of normal haemostasis?
Blood vessel walls, platelets & vWF, coagulation factors and fibrinogen
What are the main roles of platelets?
- Adhere to subendothelial proteins
- Activate and aggregate with other platelets
- Support the activation of coagulation factors
vWF =
complex adhesive plasma protein synthesized by vascular endothelium
What are the roles of vWF?
- Binds platelet surface proteins to mediate platelet adhesion
- Stabilise circulating coagulation factor VIII
Which conversion are coagulation factors important for?
Prothrombin to thrombin
What does fibrinogen do?
- Binds integrins to platelet surface
2. Converts Fibrinogen to fibrin
What are the steps to form a clot?
- Trigger
- Primary Haemostasis
- Thrombin generation
- Thrombin consolidates clot formation
What does thrombin do?
Polymerises fibrinogen to fibrin
What happens during step 1 of clot formation?
Collagen and tissue factor are exposed. vWF binds collagen
What happens during step 2 of clot formation?
Platelets adhere to vWF:collagen. Platelets activate and aggregate
What happens during step 3 of clot formation?
Tissue factors initiate thrombin generation on the activate platelets
What happens during step 4 of clot formation?
Thrombin converts fibrinogen to fibrin, this completes platelet activation. This will form a stable platelet-fibrin clot
What are the regulators of clot formation?
vWF is regulated by ADAMTS13
Thrombin is regulated by Antithrombin and activated protein C system
What are the regulators of fibrinolysis?
Thrombin activates plasminogen to plasmin. This cleaves Fibrin
What can be a feature of primary haemostasis disorders?
Abnormal skin bleeding
