Trans - Hemostasis Flashcards
hemostasis - define
process which spontaneously arrests flow of blood from vessels carrying blood under pressure - control unwanted blood flow
3 components of hemostasis
- vasoconstriction
- adhesion and aggregation of formed elements
- blood coagulation
blood coagulation - define
process resulting in formation of insoluble fibrin clot from fibrinogen in plasma
blood coagulation is determined by:
procoagulant and anticoagulant factors
problem of blood coagulation
may lead to obstruction of normal blood flow
fibrinolysis - define
degradation of fibrin clot
final common pathway
- factor Xa converts prothrombin to thrombin
- thrombin converts fibrinogen to fibrin and factor XIII to factor XIIIa
- factor XIIIa stabilizes fibrin
how does factor XIIIa stabilize fibrin?
by catalyzing formation of covalent cross links
intrinsic pathway - how is it activated
when collagen comes into contact with plasminogen following endothelial damage
intrinsic pathway
- damaged surface stimulates kininogen and kallikrein
- kininogen and kallikrein converts XII to XIIa
- XIIa converts XI to XIa
- XIa converts IX to IXa
- IXa and VIIIa converts X to Xa
- Xa leads to final common pathway
extrinsic pathway - how is it activated
activated by a tissue factor released by damaged tissues in response to trauma
what tissue factor activates the extrinsic factor
tissue thromboplastin
extrinsic pathway
- trauma induces a change from VII to VIIa
- VIIa contributes to release of tissue thromboplastin from blood vessels
- tissue thromboplastin converts X to Xa
- Xa leads to final common pathway
TPA - function
tissue plasminogen factor, converts plasminogen to plasmin
[T/F] TPA acts on all plasminogen
F, it only acts on plaminogen physically associated with fibirin
thrombus - define
blood clot formed within intravascular space during life
thrombus - may lead to:
- ischemia
2. infarction
ischemia - define
hypoperfusion of tissues
infarction - define
necrosis of tissue due to prolonged ischemia
a thrombus may fragment to yield:
thromboembolus
embolus - define
portion of material distinct from blood and carried by bloodstream from one site of the body to another
virchow’s triad
predisoposing factors to coagulation
- stasis - sluggish blood flow
- altered endothelial surface due to damage or injury
- hypercoagulability of blood
virchow’s triad - stasis may be caused by:
hyperviscosity, as in polycythemia
polycythemia - define
presence of high amount of RBCs in blood, may cause hyperviscosity
virchow’s triad - hypercoagulability may be caused by:
imbalance of coagulant and anticoagulant factors
administration of TPA is most useful when:
when it is given before fibrin cross links are formed
heparin - mechanism of action
- binds plasma protein antithrombin, inducing conformational change that enhances inhibitory effect against thrombin and Xa
- also binds thrombin, bringing it into close proximity with antithrombin
heparin interferes with what pathway?
final common pathway
heparin - how to administer
intravenously for rapid anticoagulatin
[T/F] heparin is for long-term anticoagulation
F
[T/F] warfarin is for long-term anticoagulation
T
warfarin - how to administer
orally for long-term anticoagulation
4 vitamin K dependent anticoagulant factors
9, 10, 7, 2
warfarin - mechanism of action
- vitamin K antagonist - blocks synthesis of vitamin-K dependent factors
- inhibits posttranslational conversion of glutamate to gamma-carboxyglutamate (for calcium-mediated binding to membrane surfaces)
treatment of warfarin toxicity
- fresh frozen plasma - replenishment of clotting factors (short term)
- vitamin k - restores capacity for synthesis of clotting factors (long term)
gamma-carboxyglutamate - significance
- uncommon modification of amino acids found in some functional clotting factors (e.g. vitamin-K dependent factors)
- induces affinity for calcium ions
