<prompt> Renal artery lumen is reduced by half, what will be the blood flow?Reduce by 12Reduce by 14Reduce by 116Come to normal after autoregulation  <response>: Ans: C. Reduce by 116Option c is correct because the flow of fluids can be described by Poiseuilles Law.In which flow of liquid is directly proportional to R4, So if lumen is reduced to half then blood flow will get reduce by 116.Other points related to blood flow...Poiseuilles Law states that the flow Q of fluid is related to a number of factors:The viscosity n of the fluidThe pressure gradient across the vessel PLength L and diameterr of the vesselDiameter: Doubling the diameter of tube increases the flow rate by 16 fold r4. The larger the vesselss diameter greater is the blood flow.Viscosity: Flow is inversely proportional to the viscosity of the fluid.Viscosity of blood increases with increasing hematocrit and decreasing temperaturePressure: Increasing pressure further maximizes flow as described by Poiseuilles equation.The relationship is given by Poiseuille-Hagen formula:FPA -PB x8p xe1 xLr4 WhereF FlowPA - PB Pressure difference between two ends of the tube q Viscosity r Radius of tube L Length of tubeRelationship between arterial blood pressure and blood flow given in graph below: 