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Figure 12-1 (A) The pancreas develops from two distinct buds of endodermal origin. The ventral bud originates from the hepatic diverticulum and the dorsal bud from the nascent duodenum. The foregut undergoes clockwise rotation resulting in fusion of the pancreatic buds during the sixth week of gestation. (B) The ventral bud develops into the inferior pancreatic head and the uncinate process. The dorsal bud becomes the superior pancreatic head as well as the neck, body, and tail.

Figure 12-1 (A) The pancreas develops from two distinct buds of endodermal origin. The ventral bud originates from the hepatic diverticulum and the dorsal bud from the nascent duodenum. The foregut undergoes clockwise rotation resulting in fusion of the pancreatic buds during the sixth week of gestation. (B) The ventral bud develops into the inferior pancreatic head and the uncinate process. The dorsal bud becomes the superior pancreatic head as well as the neck, body, and tail.

abnormalities that may have clinical consequences (e.g., pancreas divisum, annular pancreas, and pancreatic heterotopia).

One of the most fascinating aspects of pancreatic embryology is the development of the ductal system via which the gland's exocrine secretions enter the gastrointestinal tract. Each of the pancreatic buds (ventral and dorsal) contains a main duct that spans the length of the bud. The duct of the ventral bud, commonly referred to as the duct of Wirsung, drains into the second portion of the duodenum through the major papilla (ampulla of Vater). It should be noted that the common bile duct also empties into the duodenum through the ampulla of Vater. Autopsy studies have revealed that the distal pancreatic and common bile ducts share a short, common channel as they exit the ampulla in 85 percent of individuals.1 The pancreatic and common bile ducts exit the ampulla via separate orifices in 5 percent of cases. The duct of the dorsal bud, also known as the duct of Santorini, drains separately into the duodenum via the minor papilla.

As the ventral bud rotates and then combines with its dorsal counterpart, the proximal aspect ventral duct fuses with the distal third of the dorsal duct to form the major pancreatic duct of Wirsung that runs the length of the gland (Fig. 12-2). In most instances, the distal third of the dorsal duct (Santorini) remains in continuity with the major duct and drains the superior head of the

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Figure 12-2 The main duct of the ventral bud fuses with the main duct of the dorsal bud to form the main pancreatic duct (duct of Wirsung) that runs into the duodenum via the ampulla of Vater. The proximal segment of the dorsal bud becomes the duct of Santorini which drains through the minor papilla.

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Figure 12-2 The main duct of the ventral bud fuses with the main duct of the dorsal bud to form the main pancreatic duct (duct of Wirsung) that runs into the duodenum via the ampulla of Vater. The proximal segment of the dorsal bud becomes the duct of Santorini which drains through the minor papilla.

pancreas into the duodenum via the minor papilla (Fig. 12-2). In a smaller percentage of individuals, the minor duct of Santorini is obliterated; therefore, the entire pancreas drains via the major duct. Five percent of individuals exhibit nonfusion of the pancreatic ducts, a condition known as pancreas divi-sum. In these patients, the majority of the pancreas drains via the minor duct, a structure that is not often suited to accommodate this volume of secretions. Chronic abdominal pain due to recurrent bouts of acute pancreatitis often ensues (see section Acute Pancreatitis).

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