Question

Why does much of the pressure drop in the circulatory system occur across the arterioles (small vessels carrying blood to the capillaries) and capillaries as opposed to across the much larger diameter arteries?

Answer 1

Solution

Let us go to the basics first.

From Bernoulli equation

P + (1/2)ρV^2 + ρgh = constant.....EQN 1

From continuity eqn:

A*V = constant......EQN 2

Arterioles and capillaries have smaller diameter. So their area of cross section A is smaller. Thus, from continuity equation, we will have higher velocity V of the blood flowing in them.

Now, from Bernoulli equation, for higher velocity V, we will have lower pressure P in them. So, much pressure drop occurs across arterioles and capillaries.

Just opposite happens in case of large diameter arteries.

Thank you!!!!