Question

What is Development of Pancreas

Answer 1

epithelium of the caudal part of the foregut that forms the proximal part of the duodenum. The buds are named dorsal pancreatic bud and ventral pan­creatic bud according to their location on the duodenal wall.
The dorsal pancreatic bud is the larger of the two and appears during the 4th week of development on the dorsal wall of duodenum. It is located opposite and some distance cranial to the hepatic diverticulum. The smaller ventral pancreatic bud appears during the 5th week as an evagination from the ventral duodenal wall in the angle between the bile duct and duodenum.
The dorsal pancreatic bud (also called dorsal pancreas) grows into the dorsal mesentery of the duo­denum. Proliferation of endodermal cells at the tip of this bud forms the pa­renchyma of the dorsal pancreas. A duct system to drain the exocrine se­cretion is also formed within the devel­oping pancreatic tissue. The proximal part of the dorsal pancreatic bud re­mains tubular and serves as the main duct of the dorsal pancreas which de­livers the exocrine secretions into the duodenum.
The ventral pancreatic bud (also called ventral pancreas) grows ven-trally and, like the dorsal pancreatic bud, it also develops pancreatic tissue, a duct system and a main duct. How­ever, the size of the ventral pancreas remains much smaller than the dorsal pancreas. In some cases the ventral pancreatic bud becomes bilobed, ie, its distal part divides into two parts and, consequently the ventral pancreas be­comes bifid.
As described earlier, the C-shaped duodenal loop rotates to the right and becomes apposed to the pos­terior abdominal wall. Now the ventral pancreatic bud lies on the right and the dorsal bud on the left of the duodenum. Differential (ie, unequal) growth of the duodenal wall shifts the opening of the common bile duct to the left, so that the bile duct finally opens into the dor-somedial wall of the second part of duodenum. The ventral pancreas is carried dorsally along with the common bile duct and finally comes to lie in the mesoduodenum immediately below and behind the dorsal pancreas. The duct of the ventral pancreas opens into the dorsomedial wall of the duodenum in common with the bile duct. However, the duct of the dorsal pancreatic duct opens independently into the duode­num about 2 cm cranial to the opening of the duct of the ventral bud.
During the 7th week of devel­opment the ventral and dorsal pancre­atic buds fuse with each other to form the definitive pancreas. Major part of
the pancreas (tail, body and upper part of the head) is contributed by the dor­sal pancreatic bud. The ventral pan­creatic bud forms only the inferior part of the head and the uncinate process.
As the mesoduodenum is lost, the pancreas fuses to- the dorsal body wall and becomes retroperitoneal along with the duodenum. The connective tissue capsule and septa of the pan­creas are formed from the surrounding splanchnic mesoderm.
When the ventral and dorsal pancreatic buds fuse, their duct sys­tems also become interconnected. The short ventral duct taps the long dorsal duct. Thereafter, the long distal seg­ment of the dorsal pancreatic duct and the entire ventral pancreatic duct serve as the main pancreatic duct. To­gether with the common bile duct, the main pancreatic duct opens into the duodenum at the major duo'denal pa­pilla. The proximal part of the dorsal pancreatic duct may become obliter­ated but often persists as the acces­sory pancreatic duct, which opens into the duodenum at the minor duode­nal papilla. It is important to know that in about 10% of people the duct sys­tems of the ventral and dorsal pancre­atic buds fail to become interconnected and, thus, the original double duct sys­tem persists.
The pancreatic acini develop during the 8th and 9th week. The pan­creatic buds divide repeatedly to give rise to a large number of endodermal tubules. The pancreatic acini develop at the ends of these tubules. The islets
of Langerhans develop form cell clus­ters which become separated from the tubules and become located in be­tween the pancreatic acini. The exo-crine and endocrine secretions of the pancreas begin in the 10th week.