How does the human respiratory system work?

The human respiratory system is responsible for the exchange of gases between the body and the environment. It includes the nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs. When air enters the nose, it is warmed, moistened, and filtered by tiny hairs called cilia. From there, it travels down to the pharynx, or throat, and then the larynx, which houses the vocal cords.

After passing through the larynx, air travels down the trachea, which divides into the left and right bronchi that lead to the lungs. The bronchi then divide into smaller bronchioles that eventually lead to the alveoli, which are tiny air sacs in the lungs. It is in the alveoli that gas exchange occurs; oxygen is absorbed into the bloodstream and carbon dioxide is released from the bloodstream into the alveoli to be exhaled.

Breathing is controlled by the diaphragm, a muscle that contracts and relaxes to move air in and out of the lungs. The process of inhaling and exhaling is known as ventilation. The respiratory system also plays a role in regulating the pH of the body's fluids and in the sense of smell.