Final answer:
Lung compliance is the term that describes how easily the lungs can be stretched or expanded, which is significant for the mechanics of breathing and in pathological states, such as lung fibrosis, which decreases compliance.
Step-by-step explanation:
The term that defines how easily the lungs can be stretched or expanded is known as lung compliance. This concept is crucial in understanding not only the mechanics of breathing but also in recognizing the impact of diseases like lung fibrosis, which can make the lungs stiff and less pliable, thereby reducing lung compliance.
Several factors contribute to lung compliance, such as the ability of the diaphragm to contract and relax during inspiration, the elastic recoil properties of lung tissues, and the compliance of the thoracic wall. Pulmonary ventilation is ultimately dependent on the pressures exerted by and on the lung, impacting the volume of air moved during inspiration and expiration.
The diaphragm's movements change the thoracic volume, facilitating air movement. Conditions like lung fibrosis can alter the functional expiratory volume, which is indicated by ratios such as the forced expiratory volume (FEV1) in one second to the total forced vital capacity (FVC). Increased ratios suggest decreased compliance, which is characteristic of stiffer lungs. Furthermore, thoracic wall compliance affects how easily the thorax can expand, influencing the capacity for lung expansion during inspiration.