Now, in between the two pleura, we actually have a space. And this space, this cavity, is known as the intraplural space, or the pleural cavity. And this cavity contains a special liquid, a special fluid known as the pleura fluid. And what this pleura of fluid actually does is it not only absorbs some of the shock that the lungs might experience as a result of some type of physical damage. So it doesn't only protect our lungs, but more importantly, it actually decreases the amount of friction that the lungs experience every time they actually contract, they expand and contract. So inside this space separating our parietal and the visceral pleura, we have this parietal fluid that not only absorbs the shock and protects our lungs, but it also decreases the amount of friction that the lungs feel every time they contract and expand.