Coagulation PDF

71 COAGULATION by Daniel Haun Platelets The bottom line.....

71 COAGULATION by Daniel Haun Platelets The bottom line.. ? PRODUCTION After adhesion and aggregation a platelet plug 1. Produced from megakaryocytes is built at the injury site. The PFA test asks 2. Distribution the important question: a. 30% spleen Do the platelets properly adhere and b. 70% peripheral blood aggregate at the injury site? c. Reference range - 150,000- 400 ,000/mm3 2. Localization of the platelet plug d. Life span - 9-12 days a. Secreting platelets release arachidonic acid which converts to prostaglandin, (becomes Thrornhoxane A2) in the platelet b. Arachidonic acid is processed by adjacent endothelial cells to form platelet-inhibiting prostacyclin Platelet Precursor Cell The bottom line.. ? The platelet plug is limited to the injury site. Platelet Reference Ranges FUNCTIONS 3. Assembly and localization of the fibrin clot 1. Initial arrest of bleeding and formation a. Platelet release components include of the platelet plug fihrinogen, Factor V and Factor a. Adhesion VIII ❖ Glycoprotein lb binds to b. Fihrinogen is bound on the platelet exposed collagen surface during aggregation ❖ Requires von Willebrands factor c. Factor VIII is bound to the platelet ❖ Results in release (secretion) of surface with von Willebrand factor ADP and other granule d. Shape change exposes platelet components (including Factor V membrane phospholipid (PL); the and fibrinogen) template for the assembly of the b. Aggregation factor complexes ❖ Other platelets are stimulated b y ❖ Historically called Platelet Factor 3 ADP to undergo shape change ❖ Binds the Factor VIII and IXa (disc to sphere to pseudopods) complex (requires Ca++J - no exposing the glycoprotein Ilb I wonder Hemophilia A and Illa complex which binds Hemophilia B ( Factor VIll and fibrinogen (this is the complex IX deficiencies) are clinically that is blocked by a number of identical GP Ilb/IIIa inhibitor drugs) ❖ Binds the Factor V and Xa ❖ Fibrinogen binding links the complex; also requires Ca++ platelets; the first (and reversible) phase of aggregation ❖ With weak stimuli, the The bottom line.. ? aggregates can disassociate but strong stimuli cause the The platelet plug is a wonderful place to aggregating platelets to release produce a fibrin clot and without the platelet (secrete); with release, the presence, the fibrin won't form. It is clot aggregation is irreversible promotion and clot localization all in one.