Open the anterior wall of the duodenum along its entire length. Observe that the first part of the duodenum has a smooth surface without mucosal foldings. The remaining portions of the duodenum have large circular mucosal folds on their interior surface. On the medial wall of the descending part of the duodenum, identify the greater duodenal papilla. It is located on the longitudinal fold of the duodenum, which is formed by the common bile duct located between the wall of the duodenum and the head of the pancreas. At the apex of the greater duodenal papilla, identify the small opening for the hepatopancreatic ampulla (of Vater), through which the main pancreatic duct and common bile duct empty into the duodenum.
Superior to the greater duodenal papilla, attempt to locate the opening of the accessory pancreatic duct (of Santorini), if present, in the lesser duodenal papilla.
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