-Notice: The “Buffy coat” is the white layer between the RBCs and plasma. It is made up of WBCs which FIGHT INFECTION.

Whole blood 

   Blood in the same form as it is in the 

bloodstream 

   Not allowed to clots or separate 

    Specimen must be connected in anticoagulant tube 

    Must be mixed a minimum of two minutes just prior to test 

Hemostasis and Coagulation 

 Hemostasis refers to the processes by which blood vessels are repaired after injury. It occurs in a series of steps, from muscular contraction of the vessel walls, through clot formation, to removal of the clot when the vessel repairs itself.

          Arrest or stoppage of bleeding after injury as a body response 

            Requires coordinated interaction of endothelial cells lining blood vessels, platelets, other blood cells, plasma proteins & clotting 

Process (4 interrelated responses )

 1.) vasoconstriction 

 2.) formation of primary platelet plug 

 3.) progression to a stable blood clot 

 4.) fibrinolysis (dissolving of clot)

1.) Vasoconstriction

Rupture of a vein or artery causes an immediate vascular spasm, or contraction of the smooth muscle lining the vessel. This reduces the vessel diameter, substantially reducing the blood loss that would otherwise

occur. This contraction lasts about 30 minutes. For capillaries, this may be enough to allow the wound to seal.

2.) Formation of primary platelet plug

Exposure of materials beneath the endothelial lining causes platelets to stick to the endothelial cells almost immediately, a process known as adhesion.

Additional platelets then stick to these, a process known as aggregation. 

3.) Progression to a stable blood clot

Coagulation involves a complex interaction of enzymes and other factors whose activation ultimately results in formation of a blood clot. A meshwork of fibrin, platelets, and other blood cells that closes off the wound. The coagulation cascade begins from 30 seconds to several minutes

after the injury. 

4.) Fibrinolysis (dissolving of clot)

As the wound is closed and tissue repair commences, fibrin itself is broken down slowly, a process called fibrinolysis.

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