Coagulation Flashcards
Intrinsic pathway trigger
collagen, contact with a surface (e.g., catheter)
Extrinsic pathway trigger
TF
Intrinsic pathway factors
12, 11, 9, 8
Extrinsic pathway factors
Tissue Factor (3), 7
Intrinsic tenase:
FIX, FVIII, PL, Ca2+
Extrinsic tenase
TF, FVII, PL, Ca2+
Common pathway:
FX, FV,,Thrombin (II), Fibrin (I) - Canadian dollar denominations
Prothrombin Activator Complex
FX, FV, Ca2+, PL
What thrombin activates
FIX (intrinsic), FVIII (intrinsic), FXIII (fibrin stabilizing factor), FV (prothrombinase complex)
What the extrinsic tenase complex activates
FX, FIX (intrinsic pathway)
Role of platelets
- provide PL
- provide XIII (fibrin stabilizing factor)
- Provide Ca2+ from ER and golgi apparatus
- bind prothrombin on their surface
Vitamin K-dependent Factors
1972:
- FX (common pathway)
- FIX (intrinsic pathway)
- FVII (extrinsic pathway)
- F2 (thrombin - common pathway)
What factors does heparin inhibit
Combines with antithrombin:
Intrinsic pathway
- FXII
- FXI
- FIX
and
X (common)
What does aPTT test
- intrinsic pathway
(Table Tennis indoors) - effects of heparin
What does PT/INR test?
- extrinsic pathway
(Tennis = outdoors) - effects of warfarin
What does antithrombin do?
inhibits
- thrombin (II)
- FX
- Intrinsic pathway
- FIX
- FXI
- has heparin binding site
How do protein C and S work?
Thrombomodulin (TM) on endothelial cell surface binds thrombin
- thrombin can then activates protein C (APC)
- APC + protein S inhibits
- FV (in prothrombinase complex)
- FVIII (in intrinsic tenase)
What is Tissue Factor Pathway Inhibitor? (TFPI)
- in plasma, most bound to endothelial cells
- Inhibits FX
- FX + TFPI inhibits extrinsic pathway (TF/FVII)
- heparin increases TFPI levels in plasma
What does a TT or TCT test?
Thrombin time - localizes defect to problem with thrombin or fibrinogen
- used when aPTT and PT/INR are prolonged
Virchow’s Triad (prothrombitic factors)
- Stasis: immobility
- Vascular injury: surgery, trauma
- Hypercoagulability: inherited or acquired defect in the cascade
