Question

Describe the physical properties of the lungs and how they relate to ventilation. Be sure to explain what elasticity and compliance and relate these physical lung properties to specific aspects of ventilation. Explain they are important.

Answer 1

Physical Properties of the Lungs are as follows: Compliance, Elasticity and Surface tension.

Lung compliance is how easily the lungs can expand when there is increase in trans pulmonary pressure. Compliance is inversely related to stiffness and elastic recoil. Compliance also depends upon combination of Lung and chest wall because the lungs and chest wall expand and contract together. The compliance of the lung and chest wall combination is lower than the compliance of lungs alone or the compliance of chest wall alone. Compliance of the combination of lung and chest wall changes with lung volume. At normal resting volume the compliance is highest and at low and high volumes the compliance decreases. Compression of the chest wall at low volumes reduces compliance and at high volumes the elastic tissues in the lung makes the lungs stiff which decreases the compliance. High trans pulmonary pressure is important to increase the volume but same is not responsible for less compliance.

Elasticity of the lungs means recoiling of the lungs after it has been stretched during inhalation process. This happens because of presence of elastin and surface tension. Elastins are elastic fibres present in the connective tissues of lungs. Surface tension is formed by the fluid film that lines the alveoli. When the water gets pulled then the alveolar walls also gets pulled which causes the alveoli to recoil.