Question

Which of the following best describes the relationship between blood flows ate and vessel length ?

a) as length increases blood flow decreases

b) as length increase, blood flow decreases

c) as length decreases, blood flow stays the same

d) as length increases, blood flow increases

Answer 1

Answer : as length increases, blood flow decreases

According to Poiseuille's law, vascular resistance (R) is directly proportional to length of vessel (L) and viscosity of blood (η) , and inversely proportional to radius to the fourth power (r4)

Resistance is directly proportional to length of the vessel. When vessel length increases, resistance increases.

Resistance and blood flow are inversely proportional. When there is higher resistance, blood flow will be decreased.

So, as length of blood vessel increases, blood flow rate decreases due to higher resistance.