| Serous membranes line cavities that are closed to the outside of the body. That would include the peritoneal (abdomen), pleural (lungs), pericardial (heart), and cerebrospinal (brain and spinal cord) spaces. In each case, a thin layer of epithelial cells sitting on areolar tissue secretes fluids produced from the blood and fills the space. The fluids range from the salty solution seen around the organs of the peritoneum to the bubbly surfactant produced around the lungs. This is not the answer that I was looking for, however! Lets return to the original question. |