Select the correct statement about the physical factors influencing pulmonary ventilation: a. Surfactant helps decrease alveolar surface tension. b. As alveolar surface tension increases, additional muscle action will be required. c. A lung that is less elastic will require more muscle action to perform adequate ventilation. d. A decrease in compliance leads to more muscle effort being needed for ventilation.
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a. Surfactant helps decrease alveolar surface tension.
Extra: Pulmonary ventilation, also known as breathing, is influenced by several physical factors including surface tension, elasticity of the lung tissue, and compliance.
- **Surfactant**: This is a fluid secreted by cells in the alveoli (the tiny air sacs in the lungs) that reduces the surface tension of the alveoli. Surface tension is the attraction of liquid molecules to one another at a liquid-gas interface. High surface tension would cause the alveoli to collapse, making it difficult for gas exchange to occur. Surfactant reduces this tension, making the lungs more compliant and decreasing the effort required to inflate the alveoli during inhalation.
- **Elasticity**: This refers to how the lung tissue returns to its original position after being stretched. Lungs that are less elastic, as mentioned in option c, will indeed require more effort to inflate during inhalation. However, this would be due to decreased lung compliance (ability to stretch), which is more directly explained by option d.
- **Compliance**: If the lungs are compliant, they can stretch and expand easily. Decreased compliance, as stated in option d, means the lungs are stiffer and therefore more work is required by the respiratory muscles to bring in air, leading to increased muscle effort.
- **Alveolar Surface Tension**: This relates to option b. If alveolar surface tension were to increase, it would indeed require more muscle action to overcome the additional force needed to expand the alveoli. However, this is exactly what surfactant helps to prevent: it lowers the surface tension, thus easing the process of pulmonary ventilation.