What is the primary function of the secretions from a serous membrane, such as the pleura?

The primary function of the secretions from a serous membrane, such as the pleura, is to reduce friction between neighboring organs. Serous membranes line body cavities and cover organs, creating a smooth, lubricated surface that allows organs to move against each other without causing irritation or damage. For instance, the pleural fluid secreted by the pleura surrounds the lungs, providing a lubricated surface that facilitates lung expansion and contraction during breathing, minimizing friction against the chest wall.

This function is particularly important in areas of the body where movement occurs frequently, such as the thoracic cavity, where the lungs need to slide easily against the pleural lining during respiration. The lubrication provided by serous fluid not only protects the surfaces of the organs but also enhances their efficiency in movement.