Hemostasis Flashcards
mechanism to form blood clot at site of vessel damage
hemostasis
blood clot at site of vessel damage
thrombosis
blood clot that travels to a different location
embolus
2 parts of primary hemostasis
vascular wall
platelets
secondary hemostasis
coagulation cascade
vessel wall damage triggers what
sympathetic vasoconstriction
clot formation (2 main steps)
platelet activation
fibrin formation
plasma protein produced by EC’s and bind platelets
vWF (von willebrand factor)
normal blood smear, no platelets
arrows point to
platelets
normal parrot RBC’s
epi, collagen, thrombin, ADP, TXA2
important for platelet activation
what happens with platelets that leads to degranulation
shape changes
what determines successful degranulation
TXA2 formation from cyclooxygenase (COX)
blocks platelets from forming mature platelet plug
Aspirin
contents that platelets release during degranulation
vWF, fibrinogen, Factor V, ATP
what is required for platelets to aggregate
fibrinogen binding to platelet surface receptor GPIIb/IIIa
defect in GPIIb/IIIa and causes people to bleed
Glanzmann thrombasthenia (GT)
without this complex, can’t form platelet plug
GPIIb/IIIa
what can also activate platelets
sepsis
atheroma formation when macrophages can’t break down cholesterol; platelets come to damaged EC; vWF binds GP IIb/IIIa—> fibrinogen released, coagulation cascade—> more solid clot formed
cross talk b/t WBC’s and platelets
one leg larger than the other; erythema; warm; hurts to squeeze calf
deep vein thrombosis
what is the fear for deep vein thrombosis
pulmonary embolism
why is it red?
RBC’s trapped in platelet/fibrin net
how is clot fortified
platelet plug fortified w/ fibrin polymers
end result of coagulation cascade
fibrin formation
pathway that utilizes soluble factors
intrinsic
pathway that utilizes insoluble factors (tissue factor)
extrinsic
the intrinsic and extrinsic pathway join to form what
common pathway
site of coagulation cascade
activated platelet membrane (held together by Ca2+ ions)
sequence of hemostasis
blood vessel damage
vasoconstriction
activated platelets (plug)
coagulation cascade
factor II
prothrombin
factor IIa
thrombin
factor that converts prothrombin to thrombin
factor Xa
converts fibrinogen to fibrin monomers
thrombin (factor IIa)
factor that converts fibrin monomers to fibrin polymers
factor XIIIa
body makes this to break down clots
D-dimer
+ D-dimer test indicates
might have a blood clot
most important pathway in secondary hemostasis
extrinsic pathway
factor III
tissue factor
activates extrinsic pathway in cascade
tissue factor (factor III)
important in triggering inflammation, angiogenesis and carcinogenesis
tissue factor (factor III)
deficiency in factor IX or VIII causes what
severe bleeding
1st step in extrinsic pathway
tissue factor (factor III) binds and activates factor VII to VIIa
2nd step in extrinsic pathway
TF:VIIa activates factor X to Xa (common pathway)
3rd step in extrinsic/common pathway
factor Xa activates factor V
role of factor V
prothrombin to thrombin
what part of extrinsic pathway pulls intrinsic pathway w/ it
TF: VIIa activates IXaVIIIa complex
1st step in intrinsic pathway
factor XII is activated (XIIa)
2nd step in intrinsic pathway: factor XIIa activates what
factor XI (XIa)
factor XIa activates what
factor IX (IXa)
from both intrinsic and extrinsic pathway, what activates factor X (Xa)
IXa:VIIIa complex
due to poor nutrition and blocks factor 2,7,9,10 in coagulation cascade (bleeding)
vitamin K deficiency
inactivates thrombin (converts fibrinogen to fibrin)
anti-thrombin III
inactivates V and VIII(stops thrombin and factor X formation)
Protein C and S
breaks down clot (fibrin)
D-dimers
limits excess clot formation
fibrinolytic cascade
main player in lysing clots
plasmin
released from EC and lyses clots
t-PA
turns plasminogen into plasmin
t-PA
turns fibrin into fibrin degradation products
plasmin
deficiency of plasminogen leads to
thrombosis
deficiency in plasminogen activator inhibitors (allowing break down of clots) leads to
bleeding
normal PT (prothrombin time)
15
normal PTT
30
normal INR
1
patients on warfarin have normal PT/INR of
2.5
PT/INR of 5 worried about what
bleeding
PT/INR of 0.5 worried about what
clotting
PTT for what pathway
intrinsic to common
PT for what pathway
extrinsic to fibrin clot
how does aspirin affect bleeding time
increases it
no prothrombin to thrombin
factor V deficient
deficient in IX:VIII or no X activated
vWF disease
Hemophilia A
Hemophilia B