Your lungs are located inside the ribcage in your chest. Your diaphragm is beneath your lungs. The diaphragm is a dome-shaped muscle that works to open your lungs when you breathe.
From your nose and mouth, air travels towards your lungs through a series of tubes. The trachea or windpipe is located in your throat. The bottom of the trachea separates into two large tubes called the main stem bronchi. The left main stem bronchus goes into the left lung, and the right main stem bronchus goes into the right lung.
Inside the lung, the bronchi branch off and become smaller. These smaller air tubes are called bronchioles. There are approximately 30,000 bronchioles in each lung. The end of each bronchiole has tiny air sacs called alveoli. There are about 600 million alveoli in your lungs. Each alveolus is covered in small blood vessels called capillaries. The capillaries move oxygen and carbon dioxide in and out of your blood.
When you breathe air in or inhale, your diaphragm flattens and your ribs move outward to allow your lungs to expand. The air that you inhale through your nose or mouth travels down the trachea. Tiny hair-like structures in the trachea, called cilia, filter the air to help keep mucus and dirt out of your lungs. The air travels through the bronchi and the bronchioles and into the alveoli. Oxygen in the air passes through the alveoli into the capillaries. The oxygen attaches to red blood cells and travels to the heart. The heart then sends the oxygenated blood to the cells in your body.
When you breathe air out or exhale, the process is the opposite of when you inhale. Once your body has used the oxygen in the blood, the deoxygenated blood returns to the capillaries. The blood now contains carbon dioxide and waste products that must be removed from your body. The capillaries transfer the carbon dioxide and wastes from the blood and into the alveoli. The air travels through the bronchioles, the bronchi, and the trachea. As you exhale, your diaphragm rises and your ribs move inward. As your lungs compress, the carbon dioxide is released out of your mouth or nose.