Lecture 8- Haemostasis Flashcards
Principles of haemostasis?
Prevent bleeding and unnecessary coagulation
Make clot
Control clotting
Break it down
How does a blood clot form?
Platelets adhere to exposed collagen in the subendothelial layer with the help of Von Willebrands factor. A platelet plug is formed.
Then get secondary clot formation as amplification system results 8n thrombin converting fibrinogen into fibrin. Anticoagulants then prevent further clot formation
Four steps of clot formation
Initiation
Propagation
Amplification
Termination
Difference between intrinsic and extrinsic clotting pathway?
Extrinsic triggered by events outside vessel while intrinsic triggered by events inside vessel (platelets)
Role of vessel wall in clot formation?
Vasoconstriction
Von willebrands factor
Collagen exposure
Example of a natural anticoagulant?
Anti-thrombin
How does fibrinolysis or clot breakdown occur?
Plasminogen is converted to plasmin by plasminogen factor. Plasmin then breaks insoluble fibrin strands into D-dimers which will be elevated in DIC and DVT
What is thrombolysis?
Breakdown of a blood clot
Clinical relevance of clotting?
Bleeding disorders
Abnormal blood results
Arterial and venous thrombotic disorders
Drug therapy for pro or anti thrombotic purposes
Congenital bleeding disorders?
Haemophilia A and B
Acquired bleeding disorders?
Liver disease
Vitamin K deficiency
Anticoagulants including warfarin
What organ produces a lot of coagulation factors
Liver
Coagulation factor disorder symptoms?
Muscle haematomas Cerebral haemorrhage Haemarthrosis Bleeding post op and dental extraction Joint pain and deformity
Haemophilia A?
X-linked recessive congenital lack of factor 8. Treat with recombinant factor 8.
Haemophilia B similar except factor IX affected
Von Willebrand’s disease?
Usually autosomal dominant so males and females affected.
Platelet adhesion to vessel wall affected.
Will get gum bleeding, bruising and bleeding post surgery etc but will not get spontaneous haemarthrosis or muscle haematoma
