part of part of develops_from adjacent_to luminal space of visceral peritoneum peritoneal cavity VHOG:0000852 cavitas peritonealis BTO:0001782 In hagfishes a transverse septum extends upward from the ventral body wall posterior to the heart, partly separating an anterior pericardial cavity from a larger peritoneal cavity. (...) These basic relationships have not been modified by urodeles. The small pericardial cavity remains far forward where it is separated by a transverse septum from the principal coelom, which may now be called a pleuroperitoneal cavity because slender lungs are present. (...) The heart [of other tetrapods] is separated from the lungs (and liver if present) by more or less horizontal partitions that have their origin in the embryo as folds on the serous membrane of the right and left lateral body walls. These grow out to join in the midline of the body. They are called lateral mesocardia (birds) or pleuropericardial membranes. Posteriorly they join the transverse septum to form the adult pericardial membrane, or pericardium. (...) In their partitioning of their coelom, embryonic mammals resemble first early fishes (incomplete partition, posterior to heart, consisting of the transverse septum) and then reptiles (pericardium derived from transverse septum and pleuropericardial membranes) Mammals then separate paired pleural cavities from the peritoneal cavity by a diaphragm. The ventral portion of this organ comes from the transverse septum. The dorsal portion is derived from the dorsal mesentery and from still another pair of outgrowths from the lateral body wall, the pleuroperitoneal membranes.[well established][VHOG] GAID:24 The potential space between the parietal and visceral layers of the peritoneum, which are normally in contact. The peritoneal cavity is divided into the greater and lesser sac. The greater sac is the peritoneal cavity, and the lesser sac is the omental bursa. [TFD][VHOG] Anatomical cavity bounded by visceral and parietal peritoneum FMA:14704 EHDAA2:0001446 MA:0000054 saccus serosus peritonei EMAPA:16138 MESH:A01.047.025.600.678 uberon UMLS:C1704247 UBERON:0001179 parietal peritoneum anatomical cavity intraembryonic coelom serous cavity peritoneal sac