Hemostasis Flashcards
What are the four steps of primary hemostasis
Vasoconstriction
platelets adhesion
platelets activation
platelet aggregation
What happens in primary hemostasis step one
Nerve reflex causing smooth muscle of vessel to contract
Endothelin is secreted by endothelial cells and act on smooth muscle of vessels
Endothelium counteracts nitric oxide’s effect and prostacyclin which are vasodilators
What happens in Step two of primary hemostasis
Platelets adhere to site of injury due to damage of endothelial cells due to less prostacyclin and NO
Which factor acts as the glue that stick platelets to the surface of the endothelium
Von willebrand factor
What happens inStep 3
Platelet changes shape after activation
GP2b/3a receptor on platelets can properly bind after conformation change
Granules in the platelets are released into the blood
Dense granules secret serotonin ADP and calcium
Serotonin causes vasoconstriction
ADP activate platelets and promotes aggregation
Calcium used in secondary hemostasis to stabilize clot
Activated platelet secretes thromboxane A2 Which causes vasoconstriction and enhances platelet activation and aggregation
What happens in step 4
GP2b3a Receptor change shape and binds fibrinogen
Fibrinogen binds other GP2b3a receptor Another great lakes which creates clumping and a platelet plug
What happens in secondary hemostasis
Activation of coagulation cascade which forms fibrin from fibrinogen
Fibrin mesh formed to stabilize platelet plug
What triggers the coagulation cascade
Vessel wall injury
How is the cascades terminated
By anti-thrombotic mechanism
What’s compound dissolves the clot
-fibrinolysis
What is factor I
Fibrinogen
What is factor II
Prothrombin
What is factor III
Thromboplastin
What is factor IV
calcium
What is factor V
Proaccelerin
