intro to haemostasis Flashcards
(26 cards)
What is haemostasis?
Balanced interaction between blood vessels, blood cells, and plasma protein
What is fibrinolysis?
Dissolution of fibrin clot
What is primary haemostasis?
Interaction between blood vessels, platelets, and von Willebrand factors, leading to platelet plug
What is secondary haemostasis?
Reinforcement of the platelet plug by fibrin formation
Explain platelet production
One megakaryocyte produces 1000-5000 platelets
Thrombopoietin regulates platelet production
Explain the glycogen storage granules
High [] of proteins
Contents are released during activation
What do collagen fibres, VWF, GPIb, GPIIb/IIa and fibrinogen all do?
Adhesion
What are the steps of primary haemostasis?
Adhesion, activation, aggregation
What does von Willebrand factor do?
Bind to factor VIII to protect it
Adhesion and aggregation
Explain platelet adhesion
Exposed collagen binds to VWF
Binding GPIb complex to VWF
Trigger blood vessel to constrict
GPIa/GPVI bind to collagen
GPVI-collagen triggers platelet activation
Explain platelet activation
Stimulation causes platelet conformational change
Granule secretion
Explain platelet aggregation
Platelet crosslinking
Activated GPIIb/IIIa bind to fibrinogen on platelets
VWF binds to GPIIb/IIIa
Explain coagulation
Secondary haemostasis
Generates 3 enzyme complexes
Clotting cascade
What are the phases of coagulation?
Initiation, amplification, propagation
What is vitamin K essential for?
Synthesis of clotting factors
Explain initiation
Vessel damage leads to TF exposure
TF binds to FVIIa
Activation of FXA which activates pro thrombin to thrombin
Explain amplification
Further phospholipid exposure on activated platelets
Thrombin activates FV/FVIII, platelets, FXI
Explain propagation
Thrombin drives FV, FVII activation
Activated FVIII combines w/ activated FIX to produce tenase complex
Explain thrombin action
Stabilises coagulation
Catalyses the proteolysis of fibrinogen
Explain fibrinolysis
Removal of thrombus
Done by plasmin
What does prothrombin time (PT)?
Assess ability of plasma to form a clot based on certain components of coag pathway
What does activated partial thromboplastin time (APTT)?
Assess ability of different series of coag. proteins from those of the prothrombin to form a clot
What does thrombin time?
Thrombin acts on fibrinogen to generate fibrin, thus a clot
What does elevated PT and APTT elevated mean?
Deficiencies in multiple factors affecting more than one pathway
