Final answer:
A serous membrane secretes serous fluid which lubricates organs within closed body cavities, reducing friction to prevent inflammation.
Step-by-step explanation:
A serous membrane secretes serous fluid, which lubricates the organs in certain closed body cavities. Serous membranes include special layers called the parietal and visceral serosa. The parietal serosa lines the cavity walls, while the visceral serosa covers the organs (the viscera). These membranes secrete serous fluid into the serous space to reduce friction between the moving organs and adjacent structures. Notably, the pleura reduces friction for the lungs, the pericardium for the heart, and the peritoneum for abdominal organs.
The presence of serous fluid allows organs to move smoothly, such as during breathing or heartbeats, preventing potential inflammation from friction. These membranes line the coelomic cavities of the body, that is, those cavities that do not open to the outside, and they cover the organs located within those cavities. Serous fluid secreted by the cells of the thin squamous mesothelium lubricates the membrane and reduces abrasion and friction between organs.