hemostasis Flashcards
process which causes bleeding to stop
hemostasis
what is the goal of hemostasis
keep blood within a damaged blood vessel
the opposite of hemostasis is ?
hemorrhage
4 phases of hemostatic process
- create platelet plug
- propagation of clotting process by the coagulation cascade
- termination of clotting by antithrombotic control mechanisms
- removal of the clot by fibrinolysis
what are the 3 hemostatic system players
- blood proteins
- procoagulant factors
- anticoagulant factors - platelets
- vessel wall
- procoagulant factors
-anticoagulant factors
endogenous PLTs circulate for how long before being cleared from circulation?
~10 d
PLTs promote clotting in 2 ways:
- at site of active bleed, PLTs bind to exposed collagen to form primary plug (first response)
- after plug is formed, more PLTs come to expand and propagate the clot
secretion and granule content release and causes what? (3)
active coagulation
vasoconstriction
promote wound healing
von willebrand factor is synthesized and stored in: (2)
- endothelial cells
- PLTs
primary function of von willebrand factor
binding to other proteins
(does not require a catalytic event bc not an enzyme)
3 coagulation functions of von willebrand factor
- binds to endothelium and promotes and PLT adhesion to sites of vessel (through platelet glycoprotein Ib)
- plasma carrier for factor VIII, prevents its degradation
- binds to collagen when exposed
factor VIII is released from ___ by ____
vWF
thrombin
which hemostasis pathway is activated by tissue factor found outside the blood
extrinsic
which hemostasis pathway has factors required for activation found in the blood
intrinsic
all hemostasis pathways lead to ?
common pathway - activation of factor X
what are the 3 essential steps of blood coagulation
- prothrombin activator formed
- prothrombin activator causes conversion of prothrombin to thrombin
- thrombin converts fibrinogen to fibrin
what are the 2 ways to form prothrombin factor
extrinsic pathway
intrinsic pathway
most coagulation factors are synthesized in the ?
liver
what coagulation factors require vitamin K (6)
II, VII, IX, X, protein C, protein S
levels of vitamin K go down in: (3)
- fat malabsorption/malnutrition
- antibiotic therapy (esp. cephalosporin)
- newborn
what is a vitamin K antagonist
warfarin (coumadin)
3 steps of extrinsic pathway
- release of tissue thromboplastin from traumatized tissue
- activation of factor VII (VIIa)
- activation of factor X (Xa) = prothrombin activator (common pathway)
5 steps of intrinsic pathway
- exposure to collagen causes activation of factor XII (XIIa)
- causes activation of factor XI (XIa)
- causes activation of factor IX (IXa) with help of Calcium
- IXa, VIIIa, calcium = complex = activates factor X
- activation of factor X = prothrombin activator
prothrombin is produced continuously in ?
liver
lack of vit K or presence of liver disease prevents ?
normal prothrombin formation
fibrinogen is a protein formed in the
liver
what converts fibrinogen into fibrin
thrombin
what is the most abundant coagulation protein
fibrin (factor I)
what stabilizes the fibrin after its been converted
factor XIIIa
what protein predominantly synthesized in the liver
glycoprotein
when activated, these proteins have almost a direct effect on conversion of prothrombin to thrombin
protein C and S
anti-thrombin (III) inactivates what?
thrombin, IXa, Xa, XIa, and XIIa
4 anticoagulant plasma proteins
- protein C and S
- anti-thrombin (III)
- tissue factor pathway inhibitor
- fibrinolysis system
what is the function of the activated protein c
inhibition of factors Va and VIIIa
what is the function of tPA
conversion of plasminogen to plasmin
