Why do you have a pressure when the heart is relaxing? Like, why doesn't it just drop to zero? Because of the elastic recall of our arteries. Where do you get elastic from? From my friend, the elastic fibers that the connective tissue or the fibroblasts produce. That's the definition of an elastic connective tissue. Snaps back and continues to propagate that blood at a particular pressure generally around about 80 millimeters of mercury with a pressure. And that's where the diastolic reading comes from.