Liver

At S10, an endodermal thickening forms at the distal end of the foregut (hepatic plate). At S11, the hepatocystic diverticulum develops from this plate, and then grows into the septum transversum. At S12, the diverticulum divides into a large cranial portion (pars hepatica) and a small caudal portion (pars cystica). Endodermal cells proliferate in the hepatic part and form solid hepatic cords (hepatic parenchyma) in the mesoderm of the septum transversum. At the same time, in the septum transversum, sinusoids appear which merge to form a network connected to the umbilical and omphalomesenteric veins. The cystic part forms the gall bladder and the cystic duct. The common part of the diverticulum, originating in the duodenum, becomes the bile duct (ductus choledochus). It subdivides into the principal branches which become the hepatic duct and the cystic duct.
At S13, the spleen develops from a local thickening of mesoderm in the dorsal mesogastrium, rather than from the endoderm. The spleen subdivides the mesogastrium into the gastrosplenic and the splenorenal ligament (lymphatic organs, spleen).