What anatomical feature allows the lungs to recoil after inhalation?

The ability of the lungs to recoil after inhalation is primarily due to elasticity. The lung tissue contains elastic fibers that allow it to stretch during inhalation, accommodating the inflow of air. When the muscles involved in breathing (like the diaphragm and intercostal muscles) relax after inhalation, these elastic fibers help the lungs return to their original, smaller size. This process is crucial for effective respiration, as it aids in expelling air from the lungs during exhalation.

Other factors, such as surface tension, also play a role in lung function but are more specifically related to the mechanics of alveoli and preventing their collapse. Muscle tone refers to the state of tension in muscle fibers, which is not the key mechanism for lung recoil itself. Air pressure is involved in the process of inhalation and exhalation but does not directly contribute to the lungs' elastic recoil. The primary mechanism for this recoil is indeed the elastic properties of the lung tissue.