1. Synonym(s): ampullary crest
2. the mesodermal mass separating the pericardial and peritoneal cavities; it is covered with mesothelium except where intimately associated with the liver, which originally develops within it; the septum is definitively incorporated into the diaphragm as the central tendon.
a thick plate of mesodermal tissue that occupies the space between the thoracic cavity and yolk stalk in the early embryo, forming a transverse partition partially separating the coelomic cavity into thoracic and abdominal portions. It gives rise to the central tendon of the diaphragm.
transverse septum(1) Ampullary crest; crista ampullaris [NA6].
(2) The mesodermal tissue that separates the pericardial and peritoneal cavities.