These alveoli usually contain elastic fibers, along with collagen. There is a purpose of alveoli containing these elastic fibers. When alveoli need to be stretched, it is these elastic fibers that support stretching. When a person inhales, elastic fibers are filled with air. On the other hand, exhaling causes these fibers to spring back. At the time of exhaling, elastic fibers push out carbon dioxide. Thus, elastic fibers play a very important role in supporting the function of alveoli in human lungs and the complete respiratory process. Alveoli will not be able to do their task properly if not supported by elastic fibers.