1. Principles of Blood Coagulation
Hemostasis
Principles of Blood Coagulation
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

2. Hemostasis
The ability of the body’s systems to maintain the integrity of the blood and blood vessels
Involves:
A number of complex pathways
Platelets
Coagulation factors
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

3. Stabilized Platelet Plug
Lipemic
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4. Phases Mechanical phase
Initiated when blood vessel is ruptured or torn
Exposed subendothelium of vessel is charged
Platelets attract to this charged surface
Undergo morphologic and physiologic changes
Causes platelets to adhere to each other and the endothelium
Activated platelets expose phosphatidylserine on their outer membrane
Requires von Willebrand factor
Stabilizes the platelet plug
The adhesion and aggregation of platelets trigger the chemical phase
The initial mechanical phase is initiated by interactions of negatively charged phospholipid surfaces of cells and platelets or microparticles. Microparticles are membrane-bound cytoplasmic fragments released from platelets, leukocytes, and endothelial cells that serve to increase the surface area on which coagulation complexes can form. Tissue factor binds to Factor VIII in the plasma to initiate the coagulation reactions and Factors I-XI serves to amplify the cascade. Thrombin continues to recruit and activate more platelets, as well as trigger the conversion of fibrinogen to fibrin.
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5. Phases (cont.) Chemical phase Final phase Coagulation cascade
Involves a number of factors
Intrinsic and extrinsic pathways
Results in a fibrin mesh or clot
Final phase
Degradation of the fibrin clot
Generation of fibrin proceeds through two phases, with a soluble form generated initially and then an insoluble form consisting of cross-linked fibrin strands. The coagulation process is also modulated and resulting clots broken down through a series of interrelated reactions. In the presence of tissue plasminogen activator (tPA) and plasmin, the soluble fibrin is also broken down into fibrin degradation products (FDPs). Plasmin and tPA also act on the insoluble fibrin, producing a cross-linked version of FDPs and D-dimers. While the brief description above seems complex, the actual processes are a great deal more complicated and involve numerous additional serum proteins. The reader should refer to the recommended readings for more in-depth discussions of hemostasis.
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6. Initial Reactions for the Chemical Phase
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7. Functions of Thrombin During the Later Stages of Chemical Hemostasis and the Breakdown of Fibrin
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8. Summary of the Chemical Phase of Hemostasis
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9. Blood Coagulation Factors
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10. Summary
Hemostasis requires platelets, a number of coagulation factors, and complex reaction pathways
Mechanical and chemical pathways
Thrombin enhances recruitment and activation of platelets
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.