coagulation Flashcards
coagulation cascade is a successive series of?
amplifying enzymatic reactions
at each step in the coagulation cascade a proenzyme is?
proteolyzed to become an active enzyme, which in turn proteolyzes the next proenzyme
the end goal of the coagulation cascade leads to the activation of?
thrombin and the formation of fibrin
each reaction of the coagulation cascade depends on the assembly of what 3 complex components?
- enzyme = activation coagulation factor
- substrate= a proenzyme form of the next coagulation factor in the series
- co-factor = a reaction accelerator
components of the coagulation cascade are assembled where? held together how?
on phospholipid surface and held together by calcium-dependent interactions
the ability of factors 2, 7, 9 and 10 to bind to calcium requires what vitamin?
vitamin K
coumadin and warfarin are?
anticoagulants
Major Cascade Event
1) activation of factor X to Xa
2) factor Xa catalyzes the conversion of prothrombin to thrombin
3) thrombin converts soluble fibrinogen to insoluble fibrin, which is stabolized by factor 13
4) stailized fibrin ‘glues’ platelet plug for greater endurance
describe tissue factor (extrinsic) pathway
- occurs after vascular damage
- activated by factor 3 (tissue factor) which is exposed at sites of injury
- TF complexes with Factor 7a (extrinsic factor Xase), converging with the intrinsic pathway, leading to the activation of factor X to Xa
describe contact activation (intrinsic) pathway
- TF- factor 7a complex activates factor 9 and 9a
- factor 9a complexes with 8a (“intrinsic factor Xase”)
- also activated by factor 12 (Hageman factor)
- may be activated in the absence of tissue injury
- important in the pathogenesis of thrombosis
both intrinsic and extrinsic pathways converge to activate?
factor 10
describe common pathway
1) factor 10 is activated by factor 9a-8a complex (intrinsic factor Xase) and TF-factor 7a (extrinic factor Xase)
2) factor 10a-5a complex activate factor 2 (prothrombin) to 2a (thrombin)
3) thrombin converts fibrinogen (factor 1) to fibrin (1a)
4) fibrin clot stabilized by factor 13a
what is INR?
international normalized ratio = standardized measurement and expression of the prothrombin time
- patient PT/ mean normal PT)^ISI
- normal is 0.9-1.2
- adequate anti-coagulation generally 2.0-3.0, as high as 3.5 for high-risk conditions
INR is used to monitor for?
coumadin (warfarin) anticoagulation and screening for coagulopathies
INR reflects the activites of what factors?
2, 5, 7, and 10
Dental Procedures and Warfarin
use them! more so for outpatient dental surgery procedures like extraction or root canals
*both ACCP and BCSH agree
counter clotting mechanisms are set in motion simultaneously with?
clot formation to limit clotting to the site of injury
name 3 natural anticoagulants
1) antithrombins aka antithrimbin 3
2) Protein C and S
3) tissue factor pathway inhibitor (TFPI)
antithrombins aka antithrimbin 3 inhibit ____ and what factors?
inhibit thrombin and factors 9a, 10a, 11a, and 12a
antithrombins are activated by?
binding to heparin-like molecules on endothelial cells
ATT3 inhibits what?
inhibits thrombin and factors 9a and 10a
exogenous heparin binds to ____ resulting in its activation
ATT3
Protein C and S are vitamin ____ dependent and INactivates what factor?
vitamin K
*inactivates thrombin and factors 9a and 10a
1) fibrinolytic cascade limits size of?
2) fibrinolytic cascade mediated by?
3) fibrin split prodcuts (FSPs) act as ?
4) elevated FDPs are useful for?
1) the final clot
2) mediated by plasmin
3) fibrin split products (FSPs) can act as weak anticoagulants
4) elevated FSPs areful in diagnosing abnormal thrombotic states
plasmin is formed by?
cleaving plasminogen to plasmin by plasminogen activators
tissue plasminogen activator (tPA) is made by? most active when?
endothelial cells
*most active when attached to fibrin