Clotting cascade

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Each pathway requires what 4 components?
- enzyme
- cofactor
- calcium
- phospholiped surface
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.
What lab test is used to test the extrinsic pathway?

PT
Why is it called the extrinsic pathway?

Because TF has to be added to the pathway
What drug affects the extrinsic pathway? How?

Coumadin, by inhibiting the vitamin K dependent factors
What are the vitamin K dependent factors?

II, VII, IX, X, protein C, protein S
What does a prolonged PT time imply?
- factor VII defeciency
- liver disease
- vitamin K defeciency
- aquired inhibitor to factor VII
What lab test examines the intrinsic pathway?

aPTT
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
What drug affects the intrinsic pathway? How?

Heparin, by increasing the anticoagualtion properties of antithrombin 3
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)
What do protein C and S inhibit?

5a and 8a
How is plasmin formed?

Starts as plasminogen and is converted to plasmin by TPA (which is released by endothelial cells)
What does plasmin do?

cleaves bond in fibrin and fibrinogen (breaking up the clot)

Author

pollyannapole

20428

Card Set

Clotting cascade

Description

More info than you even wanted on how blood clots

Updated

2010-05-23T20:13:38Z

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