Meanwhile, the dorsal pancreas has extended into the dorsal mesogastrium and now borders on the primordium of the spleen. Due to the fusion of the two pancreatic primordia, there is normally only one main pancreatic duct. Along with the bile duct, this opens into the duodenum by way of the greater duodenal papilla (papilla duodeni major). The proximal part of the common excretory duct originates from the ventral pancreatic primordium. The initial dorsal pancreatic canal may also be present as accessory pancreatic duct (ductus pancreaticus accessorius). It opens into the duodenum by way of the lesser duodenal papilla (papilla duodeni minor).
The fully-developed pancreas consists of a head (caput), a body (corpus) and a tail (cauda). The posterior part of the head originates from ventral pancreatic primordium, whereas the anterior part of the head, the body and the tail come from dorsal pancreatic primordium.
It is assumed that cells in the islets of Langerhans begin producing insulin from around week 10-11.