Fun Facts Friday: Elephant Lungs The respiratory system of the elephant is quite exceptional. Elephants are the only mammals without a pleural cavity (the fluid-filled space between the lungs and chest wall). Instead, connective tissue attaches their lungs directly to the chest wall and diaphragm. This means breathing relies solely on the movement of the chest muscles rather than the expansion of the ribcage. As a result, if the lungs are constricted or if there is too much pressure on the chest