Which two factors primarily determine lung compliance?

Lung compliance is primarily determined by the elasticity of lung tissue and the surface tension present in the alveoli. Elasticity refers to the lung's ability to stretch and return to its original shape, which is crucial for proper inhalation and exhalation. When lung tissues are more elastic, the lungs can expand easily during inhalation. Conversely, if the elasticity decreases, as seen in conditions like pulmonary fibrosis, compliance also decreases, making breathing more laborious.

Surface tension in the alveoli is an equally important factor due to the presence of surfactant, a substance that reduces surface tension. Surfactant helps prevent the alveoli from collapsing and allows them to maintain stability during the respiratory cycle. High surface tension can lead to reduced compliance and can cause difficulty in breathing as the alveoli collapse more easily.

Together, these two factors — the elasticity of lung tissue and alveolar surface tension — directly affect how easily the lungs can expand and contract, thereby determining lung compliance.