abnormal embryonic tissue morphology abnormal septum transversum morphology 2013-11-13T12:52:37Z MP:0012252 MPheno.ontology any structural anomaly of the 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; the cranial part of the septum transversum gives rise to the central tendon of the diaphragm and is the origin of the myoblasts that invade the pleuroperitoneal folds resulting in the formation of the muscular diaphragm, and the caudal part of the septum transversum is invaded by the hepatic diverticulum which divides within it to form the liver and thus gives rise to the ventral mesentery of the foregut csmith