Fig. 4
From: Prepancreatic postduodenal portal vein: a case report and review of the literature
Normal development of the portal vein. The two vitelline veins are connected by three anastomoses (cranial, middle, and caudal). The dorsal pancreatic bud lies cephalad and ventral to the middle anastomosis. The duodenum lies ventral to the middle anastomosis and dorsal to the caudal anastomosis. During embryogenesis the caudal segment of the right vitelline vein and cranial segment of the left vitelline vein regress along with the caudal anastomosis. The pancreatic buds rotate in a clockwise fashion (viewed from caudal perspective) and fuse together resulting in a portal vein in the usual position posterior to the duodenum and the pancreas. C1 caudal anastomosis, C2 cranial anastomosis, D duodenum, DP dorsal pancreatic bud, LPV left portal vein, LVV left vitelline vein, M middle anastomosis, P pancreas, PV portal vein, RVV right vitelline vein, VP ventral pancreatic bud