Secretin stimulates the secretion of bicarbonate and fluids. The hormonal phase is triggered by the passage of the acidic gastric contents into the duodenal lumen and results in the release of secretin from the duodenal mucosa. The neural phase is mediated by vagal stimulation and results in the mobilization of enzymes from the acinar cells to the ducts. Pancreatic exocrine secretions are under neural and hormonal control. This provides the optimal milieu for enzymatic activity. The acinar cells secrete the enzymes responsible for the degradation of food, while the epithelial cells lining the pancreatic ducts secrete fluid and bicarbonate that render the duodenal lumen pH alkaline. The pancreatic acini and the islets of Langerhans start developing during the third month of gestation. Developmental deviation from these steps may result in clinically significant anomalies as will be discussed later.

The proximal portion of the dorsal duct forms the accessory duct of Santorini, which opens separately above the main papilla.

This duct communicates with the common bile duct before entering the duodenum via the ampulla of Vater. By the seventh week of gestation, as the two buds join, the ventral duct fuses with the dorsal duct to form the main pancreatic duct (duct of Wirsung). The ventral bud, connected to the bile duct, rotates with the duodenum and fuses with the dorsal bud. The small ventral bud contributes to the uncinate process and the inferior part of the head of the pancreas. The large dorsal bud enlarges rapidly and contributes to most of the pancreas. By the fifth week of gestation, the pancreas arises as two outpouchings from the junction of the foregut and midgut.

What is the purposes of a pancreas