Labtech

5/18/99

Clotting

• Tubes—have different colored tops
• The colors indicate what is already in tube
• Red—no additives—if draw blood, it will coagulate as soon as it reaches the tube
• Citrate—blue –see how well the blood clots
• green—heparin—inhibits thrombin (thrombin catalyzes this reaction fibrinogen® fibrin)
• purple—EDTA—ethylene diamine tetra-acetate—traps calcium ions—used when want to do anything w/the RBC's like count them
• any of these will work for our labs
• only need the plasma to see how well the blood clots

Coagulation Cascade

• platelets—if they bump into anything other than smooth, healthy endothelium
• endothelium—lining of the blood vessels—smooth squamous epithelium
• connective tissue is under the endothelium and this activates the platelets
• plaque deposits are under the endothelium and disrupt it
• activated platelet makes it sticky (phospholipids) and sticks to things that it bumped into and to other platelets
• if an activated platelet bumps into an inactivated one, it makes it active
• the accumulation of sticky platelets forms a plug (not a clot)—first line of defense to bleeding
• have 300,000/m l
• platelets starts the coagulation cascade that forms the clot
• starts on the surface of the platelets in the plug
• the platelets become part of the clot
• clotting factors—enzymes that are a part of the plasma which are not activated
• factor XII—activated by activated platelets—activated form is F. XIIa this activates F.XI