Coagulation: Basics Flashcards
what are the main steps of primary hemostasis?
- initial vessel spasm
- platelet aggregation
- fibrin formation
- initiation phase of cell model
how long does primary hemostasis take?
seconds
what does primary hemostasis culminate in?
platelet plug
what are the main steps of secondary hemostasis?
- process of clot formation
- protease cascades of the clotting factors
- amplification and propagation phase of the cell model
- intrinsic and common pathways
what does secondary hemostasis culminate in?
fibrin clot formation
how long does secondary hemostasis take?
several minutes
what is “Initiation”?
the initiation of hemostasis, when TF and VII (extrinsic pathway) –> produce small amounts of thrombin –> thrombin then activates platelets
what factors start “Initiation”?
TF and VIIa
What are the 3 major steps of platelet plug formation?
- adhesion
- aggregation
- activation
what initiates platelet plug formation?
exposure of platelets to TF and basal lamina components like collagen
what is “Adhesion”?
platelet adhesion to the surface collagen via VWF as well as directly
what is “Aggregation”?
platelet to platelet attachment, mediated by fibrin and VWF
what is “Activation” of platelets?
- degranulation –> releases vasoactive and platelet-activating mediators
- shape change –> from discs to flattened star shaped with cellular projections
- phosphatidylserine exposure on platelet surface –> essential for clotting factor binding
what does “Amplification” mean?
- thrombin and other platelet granule content activates the intrinsic pathway –> thrombin burst
- activated platelet’s surfaces act as site for attachment for VIII and V
what is propagation
activation of large amounts of thrombin –> “thrombin burst” –> large amounts of fibrinogen becoming fibrin
what are the two common models of hemostasis?
- cascade model with extrinsic/intrinsic/common pathways
- cell model with primary and secondary hemostasis
name factor I and Ia
fibrinogen and fibrin
name factor II and IIa
prothrombin and thrombin
name factor III
thromboplastin
name factor IV
iCa
name factor V
proaccelerin
name factor VII
proconvertin
name factor VIII
antihemophilic factor
name factor IX
plasma thromboplastin component
name factor X
Stuart-Prower factor
name factor XI
plasma thromboplastin antecendent
name factor XII
Hageman’s factor
which factors require Vit K for synthesis
factors II, VII, IX, and X
what factor can be synthesized outside the liver
factor VIII, but also mainly synthesized in the liver, also produced by endothelial cells
what factor is required in the largest quantities for coagulation
fibrinogen (around 2-4 g/L in blood is normal)
under what level does hypofibrinogenemia affect coagulation
levels below < 1.0 g/L
