Haemostasis Flashcards
(22 cards)
What is haemostasis?
The arrest of bleeding and maintenance of vascular patency
What are the components of a normal haemostatic system?
Formation of platelet plug
Formation of fibrin clot
Fibrinolysis
Anticoagulant defences
The formation of a fibrin clot is an example of primary/secondary haemostasis
Secondary
The formation of a platelet plug is an example of primary/secondary haemostasis
Primary
Platelets are formed in bone marrow from the budding of what?
Megakaryocytes
What is the lifespan of platelets?
7-10 days
What are the two main factors causing platelet adhesion at site of injury?
Collagen
Von Willebrand Factor
What is a reduced number of platelets called?
Thrombocytopenia
Give some consequences of failure of platelet plug formation
Purpura/spontaneous bruising
Mucosal bleeding
Intracranial haemorrhage
Retinal haemorrhage
What are examples of mucosal bleeding that may occur in failure of platelet plug formation?
Epistaxis
GI bleeding
Conjunctival haemorrhage
Menorrhagia
What is the main screening test used for primary haemostasis?
Platelet count
What is released from damaged endothelium?
Tissue factor
What occurs in the initiation stage of fibrin clot formation?
Tissue factor and VIIa activate factors V and Xa
Factors V and Xa activate what?
Prothrombin (II) to thrombin (IIa)
Thrombin will activate what?
Fibrinogen (I) to fibrin (Ia)
What occurs in the amplification stage of fibrin clot formation?
Thrombin activates VIII/IXa which increases production of V/Xa increasing production of thrombin
What causes the breakdown of fibrin?
Plasmin
What are fibrin degradation products measured as in the lab?
D-dimers
What activates plasminogen to plasmin?
Tissue plasminogen activator
What are the naturally occurring anticoagulants?
Anti-thrombin
Protein C and protein S
What occurs in thrombophilia?
There is a deficiency of naturally occuring anticoagulants
In thrombophilia there is increased tendency to develop arterial/venous thrombosis
Venous
