And as a result of this thick layer of smooth muscle it gives arteries the ability to recoil when we actually try to expand them. So what this means is when the blood actually flows through these arteries and when the blood applies a force and a pressure on the walls of those arteries as a result of that smooth muscle the walls can exert a force back on that blood and resist that expansion. So that is what we mean by recoiling back into place. So once again, arteries have a thick layer of smooth muscle which gives them the ability to recoil during expansion. This means that when the blood pushes against the walls of these arteries they can push right back. Therefore, when the blood fills these arteries and it tries to expand them the expansion doesn't actually take place or it takes place but only a very small percentage of expansion actually takes place.