The dorsal side of the stomach rotates (arrow) to the left led by the dorsal mesentery which becomes greater omentum. The rotation of the attached duodenum carries the common bile duct posteriorly and to the left, swinging the ventral pancreas with it. Anterior connection between the buds during this process is thought to be the origin of an annular pancreas which may constrict the duodenum. During this time the vitelline veins from the yolk sac are evolving into the portal vein, and the right umbilical vein regresses while the left takes a new course through the liver as the ductus venosus.
The converging pancreatic buds fuse as do their ductal systems. The distal duct of the dorsal bud (Santorini) joins the duct of the ventral bud (Wirsung) and the major flow of pancreatic juice drains into a variable common channel with the common bile duct, the ampulla of Vater. If the dorsal connection to the duodenum persists, it is usually the minor drainage route. The ventral mesentery caudal to the umbilical vein and portal structures regresses, leaving the falciform ligament ventral to the liver and the gastrohepatic (lesser) omentum between the liver and the lesser curvature of the stomach. The visceral peritoneum on the back side of the pancreas and duodenum form a fusion fascia with the dorsal parietal peritoneum.
Link to this frame from your Personal Thumbnails page?