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Learning Center
Coagulation Corner
Monday, December 1, 2008
T'was the night before....
T'was the night before a thrombosis and all through the cascade,
All the factors were quiet, not even tissue factor was made.
The red cells were flowing through the vessel by shear stress
While white cells were circulating getting ready for a mess.
.
The platelets were nestled on the endothelium ready to go-
While factor VII was waiting, ready for activation you know
And the Weibel-Palade bodies with von WIllebrand molecule
Had just settled by Protein C, which inactivates VIII as a rule
When out from the blood vessel there arose such a jolt
The platelets sprang from their resting, even thrombin started to bolt!
Away came vW factor and collagen promoting platelets to clump,
Arachidonic acid, ADP and cyclooxygenases started to jump-
The platelets began to roll along and adhere as they should-
Gave their granules the stimulus to release because they could.
When what then happened but platelet aggregation would go
Forming the phopholipid basis for secondary hemostasis you know
With activation beginning so lively and quick,
The platelets had done their job, they all were able to stick
More rapid than platelets the factors they came-
Tissue factor activating cofactors and enzymes by name-
Now FVII to VIIa and F X to Xa, calcium and phospolipid too,
On FVa and FII becomes IIa and fibrinogen you knew-
To the extrinsic pathway and the feedback with thrombin-
Now clot away, clot away, the outcome is fibrin
As amplification continues to proceed-
When now secondary hemostasis considers what it needs.
So on to the intrinsic pathway and how this one reacts
With factor IX is also activated by VIIa, that the facts.
And then platelets and cofactors FV and FVIII gets going-
The large scale thrombin generation begins flowing-
Then on to propagation, thrombin generated on the surface of a platelet-
Leading to activation of XI to XIa where explosive thrombin formation is met.
But what about contact factors? They are XII, HMWK and Prekallikrein,
This may be involved in Initiation where XIIa can activiate IX.
The IXa forms a complex with FVIIIa
In which together with phospholipid and calcium it's the complex tenase.
The final phase of making fibrin from insoluable to a clot
Required FXIII to crosslink the whole lot-
However there is still thrombin active in vivo
Thrombogenic material might breakoff and go-
This clot now so formed and solid as such-
Had finished its clotting, we don't want it too much-
So now the fibrinolytic system begins to kick in
To get rid of the clot from the RE system.
Plasmin becomes plasminogen via t-pa
So the clot can can be dissolved and go away
So the system can finish and complete it's run-
All the platelets and factors have a job that's well done.
The system is quiet and has done its best
Now factors, cofactors, platelets will all need a rest.
But do not fear, because we all know-
They will be ready to react, and ready to go-
We all hope this happens only when it is needed
And not inappropriately, and it message is heeded
Keep healthy and active and help your system work right-
Happy holidays to all-and to all a good night!
Donna Castellone
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About the Author
Donna Castellone,
MS, MT(ASCP)SH
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