Bleeding Disorders Flashcards
What is haemostasis?
The cessation of bleeding following trauma to blood vessels.
What is FIII?
Tissue factor
What is FII?
Prothrombin
What are the principle haemostatic mechanisms?
Platelet aggregation, fibrin polymerisation and vasoconstriction
What are platelets?
Small anucleate fragments
What are platelets derived from?
Megakayocytes
What do platelets respond to?
A variety of chemical stimuli
What do platelets circulate as?
Resting disks
What is VWF?
An adhesion molecule present in plasma and subendothelial matrix
What is fibrinogen?
An adhesion molecule present in the plasma
What does coagulation mean?
The solidification of liquid plasma
What is FIIa?
Thrombin
What is FI?
Fibrinogen
What is the coagulation cascade initiated by?
The exposure of blood (plasma) to a trigger which sets off a series of enzymes reactions
What is the final step in the coagulation cascade?
Polymerisation of fibrin monomers to format a gel like mesh
Why is there no factor IV?
Factor VI was discovered as calcium ions but by this time factor V had already been named
What can bleeding disorders be a result of?
Primary or secondary haemostasis
What is primary haemostasis?
Formation of a platelet plug
What is secondary haemostasis?
Consolidation of the thrombus by fibrin strands
What are the disorders of primary haemostasis?
Platelet disorders (thrombocytopenia, platelet dysfunction), von willebrands disease, connective tissue disorder
What are the disorders of secondary haemostasis?
Clotting factor deficiencies (haemophilias, liver disease), anti coagulant overdose, overactive fibrinolysis
What are the patterns of bleeding from primary haemostatic disorders?
Bleeding from skin wounds, bleeding from mucous membranes, GI bleeds, surgical bleeding, cranial haemorrhages (rare)
What are the patterns of bleeding from secondary haemostatic disorders?
Haemoarthrosis (joints), intramuscular bleeding, cranial haemorrhages (rare)
What can be noted in thrombocytopenia?
Low platelet count, impaired bone marrow function, autoimmunological destruction
What can be noted in Von Willebrand’s disease?
Qualitative or quantitative deficiency in Von Willebrand’s factor, reduced circulating factor VIII
What can be noted in Glanzmann’s thrombocytopenia/bernard-soulier syndrome?
Autosomal inheritance with varying severity, caused by defects in VWF gene.
What is thrombocytopenia?
Most common cause of defective primary haemostasis
Platelet + autoantibodies ➡ sensitised platelet = ?
Destroyed by macrophage
Haemophilia A is caused by?
FVIII deficiency
Haemophilia B is caused by?
FIX deficiency
What is haemophilia C caused by?
FXI deficiency, liver disease, vitamin k deficiency, warfarin overdose
