serous membrane

A serous membrane is a thin membrane that secretes a serous fluid. This fluid is clear to pale yellow and watery, found in the spaces between organs and the membranes that line or enclose them. Examples include the peritoneum in the abdomen and the pleura lining the thoracic cavity and lungs.123

In biology, internal membranes are crucial for distinguishing eukaryotic cells from prokaryotic cells. Eukaryotic cells, which have a nucleus, contain various organelles enclosed by internal membranes that carry out specific metabolic functions. The pleura, for instance, has a glistening surface made of mesothelial cells and secretes fluid to keep it moist. When these serous membranes become inflamed, it can lead to conditions like pleurisy or pericarditis.435