<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> In anatomy, serous membrane (or serosa) is a smooth tissue membrane consisting of two layers of mesothelium, which secrete serous fluid . The inner layer that covers organs (viscera) in body cavities is called the visceral membrane . A second layer of epithelial cells of the serous membrane, called the parietal layer, lines the body wall . Between the two layers is a potential space, mostly empty except for a few milliliters of lubricating serous fluid that is secreted by the two serous membranes . </P> <P> The Latin anatomical name is tunica serosa . Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement . Serosa is entirely different from the adventitia, a connective tissue layer which binds together structures rather than reducing friction between them . The serous membrane covering the heart and lining the mediastinum is referred to as the pericardium, the serous membrane lining the thoracic cavity and surrounding the lungs is referred to as the pleura, and that lining the abdominopelvic cavity and the viscera is referred to as the peritoneum . </P> <P> A serous membrane (also referred to as a serosa) is one of the thin membranes that cover the walls and some organs of the thoracic and abdominopelvic cavities . Serous membranes have two layers . The parietal layers of the membranes line the walls of the body cavity (pariet - refers to a cavity wall). The visceral layer of the membrane covers the organs (the viscera). Between the parietal and visceral layers is a very thin, fluid - filled serous space, or cavity . </P>

Two thin membranes surround the lungs. what are these membranes known as