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Type:
Educational Exhibit
Keywords:
Abdomen, Anatomy, Pancreas, CT, MR, Normal variants, Imaging sequences, Congenital
Authors:
R. Ouji1, O. Ghdes2, A. Ali2, I. Kasraoui2, N. Achour2, A. Gaja2, N. Mnif2; 1Oued Ellil/TN, 2TUNIS/TN
DOI:
10.1594/ecr2017/C-2154
Background
1-Embryology of pancreas: Fig. 1
- The pancreas develops as two separate outgrowths from the primitive digestive tube.
It develops from dorsal and ventral buds that arise from the foregut during the fifth week of embryonic development.
- The ventral and dorsal buds develop on opposite sides of the primordial foregut.
- The ventral bud forms as an outpouching of the liver diverticulum.
- The two pancreatic buds develop independently,
each with a dominant duct draining into the duodenal lumen.
- The main pancreatic duct forms as the dorsal pancreas grows,
beginning in the tail region at the convergence of small tributaries.
- During the sixth week,
the dorsal bud elongates and grows into the dorsal mesentery.
The ventral bud is carried away from the duodenum by growth of the liver bud and development of the common bile duct.
The common bile duct and the ventral bud rotate counterclockwise around the duodenum because of its eccentric growth,
eventually being located just caudal and posterior to the dorsal bud.
- At about 7-weeks,
the two pancreatic components fuse.
⇒The dorsal bud forms: the pancreatic body,
tail and anterior portion of the head of the pancreas.
⇒The ventral bud becomes: the uncinate process and the posterior portion of the pancreatic head
- When the two portions of the gland fuse,
their ducts also fuse :
⇒The main pancreatic duct in the neck,
body and tail originates from the dorsal pancreas and that in the head from the ventral pancreas.
⇒The remaining portion of the dorsal pancreatic duct forms the accessory pancreatic duct (the duct of Santorini),
which drains separately into the duodenum and maintains a variable connection with the main pancreatic duct.
⇒The ventral duct downstream from the fusion point is called the duct of Wirsung
- The main biliary tract as well as the main pancreatic duct meet at the level of the major papilla Fig. 2.
2/-Normal anatomy:
- The pancreas is located in the retroperitoneal space and it is divided to 4 portions:
⇒The head (adjacent to the left wall of the second portion of the duodenum)
⇒The neck
⇒The body
⇒The tail (directed toward the splenic hilum)
- The uncinate process is a continuation of the head caudally and is located cephalad and anterior to the third portion of the duodenum.
It is the portion of the pancreatic head,
behind the superior mesenteric vein and the superior mesenteric artery.
- Different lines Fig. 3 define the boundaries between the head,
the neck and the body of the pancreas:
⇒Borders between the head and the neck of the pancreas: Line joining the origin of the gastroduodenal artery to the right edge of the superior mesenteric vein
⇒Borders between the neck and the body of the pancreas: Line parallel to the previous one that is tangent to the left edge of the superior mesenteric vein
⇒Borders between the body and the nail of the pancreas: Longitudinal line from the point where the splenic vein crosses the upper edge of the pancreas
- The main pancreatic duct runs from the tail to the pancreatic head,
supplied by numerous small tributaries that enter at right angles from the pancreatic parenchyma.
- Most commonly,
the ducts are fused at the neck,
with predominant drainage through the duct of Wirsung,
emptying at the major papilla.
- The accessory duct may contribute some drainage through the minor papilla.
If the minor papilla is not patent,
the duct of Santorini acts as a tributary,
draining the anterior pancreatic head into the main duct.