Serous membranes are thin layers of tissue that line certain cavities in the body and cover the organs within those cavities. They produce a fluid called serous fluid, which helps reduce friction between the organs and surrounding structures, allowing them to move smoothly during activities like breathing and digestion. These membranes are found in three main areas: the pleura around the lungs, the pericardium around the heart, and the peritoneum in the abdominal cavity. Each serous membrane consists of two layers: the visceral layer that covers the organs and the parietal layer that lines the cavity walls.