Haemostasis Flashcards
What is haemostasis?
The process of arresting bleeding and the maintenance of vascular patency.
What is primary haemostasis?
The formation of a platelet plug.
In small injuries this may be sufficient to stop bleeding.
What is secondary haemostasis?
Formation of a fibrin clot.
Occurs in larger injuries, preventing the platelet plug being washed away.
What is fibrinolysis?
The breakdown of the fibrin clot due to the blood vessel being secured.
This aims to prevent blockage of the blood vessel.
From what cells do platelets arise?
Megakaryocytes
How long do platelets live?
7-10 days.
Short lifespan due to lack of nucleus.
How long do antiplatelets affect platelets?
Affect full lifespan, meaning antiplatelets should be stopped 7-10 days prior to surgery to prevent bleeding.
What is released when collagen exposed following endothelial injury?
Von Willebrand factor
This allows platelet to stick the site of injury.
What can cause failure of the platelet plug to form?
Vascular - may lack collagen.
Platelets - may have reduced number or function.
Von Willebrand factor deficiency
How does platelet plug failure present?
Increased bruising and purpura of the peripheries.
Produces a non-blanching rash.
What can cause fibrin clot formation?
Missing a single clotting factor.
Missing multiple clotting factors.
What can be a consequence of an increased rate of fibrinolysis?
Use up clotting factor levels.
Occurs in disseminated intravascular coagulation.
What is the molecule responsible for fibrinolysis?
Plasmin
When fibrinolysis occurs, what is released?
D-dimers
Level present is indicative of the rate fibrinolysis.
What is missing in haemophillia?
A single clotting factor
