not to be confused with perineum.  the peritoneum  is the serous membrane that forms the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. it covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothelium supported by a thin layer of connective tissue. the peritoneum supports the abdominal organs and serves as a conduit for their blood vessels, lymph vessels, and nerves. the abdominal cavity (the space bounded by the vertebrae, abdominal muscles, diaphragm, and pelvic floor) should not be confused with the intraperitoneal space (located within the abdominal cavity, but wrapped in peritoneum). the structures within the intraperitoneal space are called "intraperitoneal" (e.g. the stomach), the structures in the abdominal cavity that are located behind the intraperitoneal space are called "retroperitoneal" (e.g. the kidneys), and those structures below the intraperitoneal space are called "subperitoneal" or "infraperitoneal" (e.g. the bladder). ==structure== ===types=== although they ultimately form one continuous sheet, two types or layers of peritoneum and a potential space between them are referenced: * the outer layer, called the parietal peritoneum, is attached to the abdominal wall and the pelvic walls.tank, p. (2013) grants dissector 15th ed., ch.4 the abdomen, p.99 * the inner layer, the visceral peritoneum, is wrapped around the internal organs that are located inside the intraperitoneal space. it is thinner than the parietal peritoneum. * the potential space between these two layers is the peritoneal cavity; it is filled with a small amount (about 50 ml) of slippery serous fluid that allows the two layers to slide freely over each other. * the term mesentery is often used to refer to a double layer of visceral peritoneum. there are often blood vessels, nerves, and other structures between these layers. the space between these two layers is technically outside of the peritoneal sac, and thus not in the peritoneal cavity. ===subdivisions=== peritoneal folds are omenta, mesenteries and ligaments; they connect organs to each other or to the abdominal wall.drake et 
Abdomen