The peritoneum is a large serous membrane, which forms in the male a closed sac, the parietal layer of which lines the abdominal walls, its visceral layer being reflected more or less completely over all the abdominal and pelvic viscera. It's free surface is covered with endothelium, and is smooth, moist, and shining. Its attached surface is connected to the viscera and the parietes of the abdomen by the sub-peritoneal tela or areolar tissue. In the female it is not a closed sac, the free extremities of the Fallopian tubes opening directly into the cavity. The peritoneum is divided by a constricted portion of its tissue, at the foramen of Winslow into 2 sacs, the Greater Sac and the Lesser Sac.