Question

Explain how flow through a blood vessel is determined. Explain what a “pressure difference” is and why it matters to flow. Define resistance and explain how resistance affects flow. List and discuss the 3 factors which influence the resistance through vessels. For each factor explain the mechanism by which it affects resistance. Which one of these 3 as the largest impact on resistance? Explain why it has the largest impact on flow. Which one of these 3 can readily be adjusted by the body?

Answer 1

Blood Flow

Blood flows in the same direction as the decreasing pressure gradient: arteries to capillaries to veins. The rate, or velocity, of blood flow varies inversely with the total cross-sectional area of the blood vessels. As the total cross-sectional area of the vessels increases, the velocity of flow decreases.

Pressure Difference – Delta P (ΔP) Delta P (ΔP), pressure difference or differential pressure usually refers in the technical world to the drop of pressure in a piping system, a heat exchanger or another machine, where a liquid is passing through.

FACTORS WHICH INFLUENCE THE RESISTANCE:

There are three important sources of resistance: vessel length, blood viscosity, and vessel diameter. Let's discuss blood vessel length first. Resistance, as it pertains to total blood vessel length is easy: The longer the blood vessel, the greater the resistance.

First, the total length of the wires will affect the amount of resistance. Second, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe.