Pancreas

The pancreas is formed from two primordia arising from the endoderm of the duodenum. The dorsal pancreas is first to form (S12), on the dorsal surface of the duodenum. It grows quickly into the mesoduodenum. The ventral pancreatic bud is formed a little later (S13-14) in the angle under the hepatic anlage from the primordium of the bile duct.
Most of the ventral pancreatic primordium is in contact with the hilum of the liver (porta hepatis), but it can also have direct contact with the duodenum. Together with the stomach, the duodenum undergoes a rotation of around 90 degrees. At the same time, the ventral pancreatic primordium moves away from the duodenum as the bile duct (ductus choledochus) grows. The opening of the hepatopancreatic duct in the duodenum shifts dorsally. These growth processes cause the ventral pancreas to attach to the dorsal pancreas, and these fuse together to create a single organ (S17).