Haemostasis Flashcards
what are the requirements of haemostasis
permanent state of readiness
prompt response
localised response
protection against unwanted thrombus
what are the components of a normal haemostatic system
formation of platelet plug (primary Haemostasis)
formation of fibrin clot (secondary Haemostasis)
fibrinolysis
anticoagulant defences
from which cells do platelets arise
megakaryocytes
what is the average lifespan of a platelet
7-10 days
what causes platelet adhesion
damage to endothelial surface (vessel wall) exposes collagen and VW factor which have platelet receptors
what causes platelet aggregation
secretion of chemical by platelets
what are the consequences of failure of platelet plug formation
spontaneous bruising and purport
mucosal bleeding (epistaxes, GI, conjunctival, menorrhagia)
intracranial haemorrhage
retinal haemorrhages
what screening tests can be done for assessment of primary Haemostasis
platelet count
which factors are involved in the extrinsic coagulation pathway
tissue factor and VII
which factors are involved in the intrinsic pathway
VIII and IX
which factors are involved in the common pathway
V and X
prothrombin
fibrinogen
what are the causes of failure of fibrin clot formation
single clotting factor deficiency
multiple clotting factor deficiency
increased fibrinolysis
what causes fibrinolysis
plasminogen is converted to plasmin in the presence of tissue plasminogen activator
plasmin breaks down fibrin to fibrin degradation products
what screening tests are available for secondary Haemostasis
prothrombin time
activated partial thromboplastin time
which pathway does prothrombin time measure
extrinsic
