Pulmonary alveolus. What does the Mucosa do? Mucosa: MedlinePlus Medical Encyclopedia. Trachea. Human Respiratory System and Lungs; How They Work. You usually don't even notice it, but twelve to twenty times per minute, day after day, you breathe -- thanks to your body's respiratory system.
Your lungs expand and contract, supplying life-sustaining oxygen to your body and removing from it, a waste product called carbon dioxide. The Act of Breathing.