explain machnisum of exlation

In human beings, air is taken into the body through the nostrils, is filtered by fine hairs that line the passage. When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by nasal hair and mucus so that clean air goes into the lungs. From here, the air passes through the throat and into the lungs. Trachea does not collapse even when there is no air in it because it is supported by rings of soft bones called cartilage.
Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels. When we breathe in, the ribs are lift up and the diaphragm flattens which increases the size of the chest cavity. Because of this, air is sucked into the lungs and fills the expanded alveoli.