We can also use a measurement known as compliance to describe the behavior properties of blood vessels. So let's begin by defining what compliance is. So compliance, loosely speaking, describes how easy it is to actually expand a given blood vessel. So if we take a blood vessel and we try to expand that blood vessel by increasing its crosssectional area and if that blood vessel is able to resist it and recall back into its original position then in this case we say that the blood vessel has a low compliance. On the other hand, if by trying to expand that blood vessel the blood vessel remains in that expanded state and doesn't recoil back into place well, in this case we say the blood vessel has a high compliance. So high compliance means we have to apply a low pressure to expand it.