What is the primary role of the pleural membrane?

The primary role of the pleural membrane is to lubricate the surfaces of the lungs and thorax. This membrane consists of two layers—the visceral pleura that covers the lungs and the parietal pleura that lines the chest wall. Between these layers lies the pleural cavity, which contains pleural fluid. This fluid serves several crucial functions: it reduces friction between the lungs and the thoracic wall during breathing, allowing the lungs to expand and contract smoothly without irritation or damage. Additionally, the pleural fluid helps maintain pressure and provides a cohesive force that keeps the lungs inflated against the thoracic wall.

While stabilizing lung position and protecting against infection are important functions in the overall physiology of the respiratory system, they do not accurately describe the primary function of the pleural membrane. Similarly, although gas exchange is a vital process that occurs in the alveoli of the lungs, it is not directly related to the role of the pleural membrane.