The Origin of the Liver. Disclosure 14
The liver together with the intestine are two organs of vital importance in the current pig and poultry production and its origin is vital to understand its operation.
Two aspects must be distinguished: the embryological origin and phylogenetic origin
From the embryological point of view, different hepatic tissues are originated at the level of duodenum from cells coming from the endoderm. This means they are specialized epithelial cells. The first cell group is called liver bud and is inverted Y-shaped. The cranial branch leads to liver and hepatic duct while one of the two branches (back) causes the gallbladder and cystic duct . The second branch flow (above) causes the common bile duct that holds the liver and the duodenum.
From the phylogenetic point of view, mesenteric glands can be found, connected to the stomach in scaphopods (monoplacophorans heirs and thus related to the ancestral mollusc) and hepatic diverticulum in Amphioxus. So we can therefore indicate that the origin of the liver is in some primitive mesenteric glands that would arise in parallel or shortly after the stomach, as derivation of the intestine in the Cambrian period between 525 and 500 million years ago.
Finally we note the importance of "Notes on the origin of the Liver" published by Thomas W. Shore, Anatomy and Physiology Journal in January 1891.