Blood Coagulation Flashcards
Steps of hemostasis
- Initiation
- Localization
- Propagation/amplification
- Termination
- Elimination
Vessel wall - endothelial cells and subendothelial components
Initiation
Platelets- circulating cellular elements
Localization
Plasma coagulation proteins (factors)
Propagation/Amplification
Plasma coagulation protein inhibitors
Termination
Fibrinolytic system
Elimination
Clinical test to to assess the functionality of intrinsic pathway, Used to test for common congenital hemophilias (deficiencies in IX, VIII, or XI) and to monitor heparin treatment
activated partial thromboplastin time (APTT)
Normal time range for APTT test
30-50 seconds
Prolongations in the aPTT are observed in deficiencies of factors…
XI, IX, VIII, X, and V, prothrombin, or fibrinogen
In APTT test ____ and ____ are added to the test plasma sample
Kaolin and cephalin
Refers to tissue factor, which is expressed on subendothelial cells
Extrinsic pathway
Clinical test to assess the functionality of the extrinsic pathway.
Prothrombin time (PT) Used to test for the rare congenital deficiencies: More often it is used to diagnose acquired bleeding disorders resulting from vitamin K deficiency, oral anticoagulants (e.g. warfarin), and liver disease
Added to test plasma sample in PT test
Lipidated tissue factor
Normal range for PT test
10-15 seconds (shorter pathway)
Prolongations in the PT are observed in deficiencies of
factors VII, X, V, prothrombin, or fibrinogen.
Deficiencies in all of the factors, except factor , lead to a bleeding tendency in the affected individual
XII
Activated factor enzymes are designated with an
“a” e.g. factor Xa
sequence of zymogen to enzyme conversions, with each enzyme activating the next zymogen in the sequence
waterfall or cascade
Roles of thrombin
- Cleaves Fibrinogen
- Activates Platelets
- Activates procofactors (FV and FVIII)
- Activates zymogens (FVII, FXI and FXIII)