In: Anatomy and Physiology
If the radius of a blood vessel decreases by 30% (1/3), how does it effect blood flow?
According to Hagen–Poiseuille equation
blood flow rate through the vessel depends on the difference in the pressure and the blood flow resistance
flow rate = change in the pressure between the two end of vessel / blood flow resistance
blood flow resistance =8 *N*L/( pi * R4)
Where N is the viscosity and L is length of the vessel and R is the radius of the vessel
From this,
the flow rate is directly proportional to Radius4
let us assume the initial radius be R
when the radius is decreased by 30% , the new radius will be
R - 30% R = R-1/3R = 2/3 R
FLOW RATE IS PROPORTIONAL TO R4
SO, THE NEW FLOW RATE WILL BE PROPORTIONAL TO (2/3R)4
THAT IS NEW FLOW RATE = (2/3)4 * OLD FLOW RATE
= 16/81* OF FLOW RATE =0.2* FLOW RATE
that is the flow rate is decreased by 80%
CONCLUSION
WHEN THE RADIUS IS DECREASED BY 30%, THE NEW FLOW RATE BECOME 0.2TIMES OF THE OLD FLOW RATE. THAT IS THE FLOW RATE IS DECREASED BY 80%