Why do lungs become stretched?

The elasticity of the lungs contributes to the stretching process due to its unique tissue composition. The presence of elastic fibers, particularly elastin, allows the lungs to expand and contract during inhalation and exhalation. These fibers are responsible for maintaining the lung's shape and recoiling after each breath.

During inhalation, the diaphragm contracts and the chest expands, creating negative pressure within the thoracic cavity. This pressure difference encourages air to rush into the lungs through the airways, causing them to inflate. As the lungs expand, the elastic fibers stretch and store elastic potential energy.

Upon exhalation, the diaphragm relaxes, and the chest cavity contracts, resulting in a decrease in lung volume. The stored elastic energy in the stretched fibers is released, promoting the recoil of the lung tissue. This recoil generates a force that helps expel the air out of the lungs, facilitating the process of exhalation.

The balanced interplay between the elastic recoil of the lungs and the surrounding muscles ensures that the lungs can effectively expand and contract, allowing for the exchange of oxygen and carbon dioxide during respiration.