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Each pathway requires what 4 components?
- enzyme
- cofactor
- calcium
- phospholiped surface
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The extrinsic pathway begins with tissue factor (TF) and factor VIIa. Where is TF derrived from?
- brain
- TF is on subendothelial surfaces and in monocytes. It is released by damage to blood vessels or when monocytes are exposed to endotoxin.
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What lab test is used to test the extrinsic pathway?
PT
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Why is it called the extrinsic pathway?
Because TF has to be added to the pathway
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What drug affects the extrinsic pathway? How?
Coumadin, by inhibiting the vitamin K dependent factors
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What are the vitamin K dependent factors?
II, VII, IX, X, protein C, protein S
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What does a prolonged PT time imply?
- factor VII defeciency
- liver disease
- vitamin K defeciency
- aquired inhibitor to factor VII
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What lab test examines the intrinsic pathway?
aPTT
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What are the steps of the intrinsic pathway?
- 11 to 11a
- which catalyzes 9 to 9a
- using cofactor 8, 9a (plus Ca plus Pl) transforms to 10
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What drug affects the intrinsic pathway? How?
Heparin, by increasing the anticoagualtion properties of antithrombin 3
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What are the steps of the common pathway?
- 10 to 10a
- 10a +5a (+Ca+Pl) =2 (prothombin)
- 2 (prothrombin) to 2a (thrombin)
- 2a becomes a catalyst for converson of fibrinogen (2) to fibrin (with the help of factor 13)
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What do protein C and S inhibit?
5a and 8a
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How is plasmin formed?
Starts as plasminogen and is converted to plasmin by TPA (which is released by endothelial cells)
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What does plasmin do?
cleaves bond in fibrin and fibrinogen (breaking up the clot)
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