And the inner membrane of the pleura is known as the visceral pleura. And in between these two membranes, we have the space we call intraplural space, or our intraplural cavity. And inside this cavity, we basically have a special type of fluid that decreases the friction that exists as a result of that process of breathing. Now, these structures are basically the ribs and this is our ribcage. Now, in between the ribs, we have these red portions, and that is the external intercostal muscle, a type of skeletal muscle. And beneath the lungs, we have another type of skeletal muscle we call the diaphragm.