The transverse septum is considered one of the forerunners of the diaphragm an embryonic structure located on the 23rd day of embryonic development below the heart plant as a broad, horizontal thickening of the mesoderm forms and chest incomplete in the abdominal cavity defines, as both sides of the foregut as Gaps called pericardioperitoneal or coelom canals remain.
From the 24th day , liver parenchymal cells originating from the endoderm begin to grow into the transverse septum and penetrate it in such a way that there is a variety of interactions between the two types of tissue and ultimately the connective tissue structures of the liver as well as their blood-forming cells and the Kupffer cells are derived from the transverse septum . In animal cells, for example. For example, it can be demonstrated that these tissue interactions between the hepatic endoderm and mesenchyme enabled the differentiation of the liver cells, whereas the culture of endoderm cells alone did not allow this. Some cytokines and transcription factors have meanwhile been identified as mediators of these processes.