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What is Which of the following produces VWF: and explain in detail?
Ans. (A) Endothelial cells(Ref: Robbins and Cotran Pathologic Basis of Disease 10th ed; Pg 489)Synthesis of VWF is large multimeric glycoprotein in blood plasma and produced constitutively as ultra-large VWF in endothelium (in the Weibel-Palade bodies), megakaryocytes and platelets (a-granules of platelet), and subendothelial connective tissues.Function of von Willebrand FactorTwo critical functions in primary hemostasis: It acts as a bridge molecule at sites of vascular injury for normal platelet adhesion and under high shear conditions, it promotes platelet aggregation.VWF has a third function that is important in fibrin formation, acting as a carrier for factor VIII in the circulation that maintains the normal level of factor VIII by decreasing the clearance of factor VIII fivefold.Prolongs the half-life of factor VIII by stabilizing it (half-life of vWF - 24 hrs when free and 12 hrs when bound to vWF in the circulation).Ristocetin induces multivalent vWF multimers to bind platelet glycoprotein Ib-IX and forms interplatelet bridges.Von Willebrand disease - Most common inherited bleeding disorder of humansType 1 and 3 are due to quantitative defects in vWFType-2 is due to qualitative defect in VWF.