What gases are excreted by the lungs?

The lungs primarily excrete carbon dioxide (CO2) and water vapour (H2O).

The lungs play a crucial role in the respiratory system, which is responsible for the exchange of gases between the body and the environment. The primary gas excreted by the lungs is carbon dioxide, a waste product of cellular respiration. During this process, glucose and oxygen are used to produce energy, with carbon dioxide and water as by-products. These by-products need to be removed from the body to maintain a stable internal environment, a process known as homeostasis.

When we inhale, oxygen-rich air enters the lungs and is absorbed into the bloodstream through tiny air sacs called alveoli. Simultaneously, carbon dioxide, which is carried by the blood from the body's tissues to the lungs, diffuses from the blood into the alveoli. This carbon dioxide is then exhaled from the body. This process of gas exchange is facilitated by the thin walls of the alveoli and the extensive network of capillaries that surround them.

In addition to carbon dioxide, the lungs also excrete water vapour. This is a result of the humidification of the air that we breathe in. As the air travels through the respiratory tract, it is warmed and saturated with water vapour. This humidified air is then exhaled, along with the carbon dioxide, from the body.

In summary, the lungs are essential for the removal of waste gases from the body. They primarily excrete carbon dioxide, a by-product of cellular respiration, and water vapour, which is added to the air during its passage through the respiratory tract.