Question

How is compliance related to wall tension in the wall of a vessel? Which type vessel is more compliant: veins or capillaries? And what property allows these vessels to be more compliant?

Answer 1

How is compliance related to wall tension in the wall of a vessel?

Ans. The capacity of a blood vessel to extend and increase volume with the changes in pressure is called as Vessel compliance (C)

Wall tension is inversely proportional to the wall thickness which means thicker the vessel wall, lower is the tension and thinner the vessel wall higher is the tension

Vessel compliance is given by the equation C=

where V is the change in volume, P is the change in pressure

Which type vessel is more compliant: veins or capillaries?

Ans. Capillaries (if arterioles or venules taken into consideration) contain only one layer of wall while veins contain three layers of cell wall. In other words veins are thicker than capillaries (if arterioles or venules taken into consideration), according to the discussion in the first question, higher the thickness lesser is the compliance.

In Veins vs Capillaries, capillaries are more compliant due to their thinner cell walls

But In Veins vs Arteries, Veins are more compliant when compared to the arteries as veins have thinner cell walls when compared to arteries. Arteries require large change in pressure for a small change in shape

Please Note that The main dogma is thicker the cell wall lesser is the compliance. If there is any ambiguity in the question because the word "capillaries" was given and did not specify whether the capillary artery or arteriole or venule both the answers were provided in the answer.

And what property allows these vessels to be more compliant?

Thinner walls in the veins when compared to arteries make them more compliant than arteries. They require only a small pressure for a large change in shape.