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.
hog:0000565 septum transversum hepatic componenthog:0000566 septum transversum non-hepatic componentBFO:0000050 part of
hog:0000170