 When they fill with gases (such as air) or liquids (such as blood) in pathological ways, they can suffer conditions such as pneumothorax, edema, or pericardial effusion.Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realization being dynamic according to physiologic or pathophysiologic events).In other words, they are like an empty plastic bag that has not been opened (two walls collapsed against each other; no interior volume until opened) or a balloon that has not been inflated.