And that means they are not actually built to withstand any high pressure like our arteries are built. And in fact, because within the capillaries we have an exchange of nutrients and waste products taking place. That basically means is for that exchange to take place efficiently the flow of the blood within the capillaries has to be relatively slow. So the reason that we need a drop in pressure is to make sure that the pressure and the rate at which our fluid is flowing within the capillaries is low so that the capillaries don't actually pop and so that the capillaries can actually exchange those nutrients and waste products effectively and efficiently. Now, one quick way that I can explain why the velocity within the capillaries is low is by using something called the continuity equation. The continuity equation, Q equals AV, comes from fluid dynamics, comes from physics.