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Physiology

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Cardiovascular System

Question
14 out of 16
 

Blood flow through a vessel varies directly with



A Resistance
B Viscosity

C Pressure of difference
D Length of vessel

Ans. C Pressure of difference

1. Flow in any portion of the vascular system is equal to the effective perfusion pressure in that portion divided by resistance.

The effective perfusion pressure is the mean intraluminal pressure at the arterial mean minus the mean pressure at the venous end]

Flow = Pressure

Resistance

2. Indirect methods for measuring blood flow — are

a. Fick and indicator dilution techniques

b. Cerebral blood flow kety N2O method

c. Renal blood flow by measuring clearance of PAHA

d. Blood flow in extrimtes —by Plethysmography

1. Poiseuille-Hagen formula - the relation between flow in along narrow tube, viscosity of fluid, and radius of the tube

F = flow

PA — PB Pressure difference between the two ends of the tube

η = viscosity

r = radius of tube

L = Length of tube

R (Resistance) = 8ηL/ πr4

From above it is clear that flow is directly varies with pressure difference and radius (r4) and indirectly varies with viscosity of fluid, resistance and length of tube Q

Cardiovascular System Flashcard List

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