Inclusive Anatomy
Structure:
The sphincter of the hepatopancreatic ampulla is a specialized smooth muscle complex located at the junction of the common bile duct and the main pancreatic duct as they enter the descending (second) portion of the duodenum.[1,2] It surrounds the terminal segment of the hepatopancreatic ampulla and regulates the opening at the major duodenal papilla.
Structurally, the sphincter consists of circular and longitudinal smooth muscle fibers organized into three components:
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The sphincter of the bile duct
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The sphincter of the pancreatic duct
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The sphincter of the ampulla.[3]
These components function together to coordinate the flow of biliary and pancreatic secretions into the duodenum.
Important spatial relationships include its position within the wall of the duodenum, its proximity to the head of the pancreas, and its continuity with the hepatopancreatic ductal system.[2]
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Function:
The sphincter of the hepatopancreatic ampulla regulates the release of the bile and pancreatic enzymes into the duodenum in response to hormonal and neural stimulation.[3] It prevents reflux of duodenal contents into the biliary and pancreatic ducts, thereby reducing the risk of ascending infection such as cholangitis.[3]
During fasting, tonic contraction of the sphincter facilitates retrograde filling of the gallbladder, allowing bile storage and concentrated. Following food intake, cholecystokinin stimulates gallbladder contraction and sphincter relaxation, permitting bile and pancreatic secretions to enter the duodenum.[3]
Clinically, dysfunction of this mechanism, referred to as sphincter of Oddi dysfunction, may result in biliary pain, pancreatitis, or ductal obstruction. The sphincter is also a key anatomical landmark in endoscopic retrograde cholangiopancreatography (ERCP), where accurate identification is required for safe
cannulation.[3]
References:
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Thiessen NW. The anatomy of the sphincter of Oddi. Am J Surg. 1941;53(1):94-101. doi:10.1016/S0002-9610(41)90454-3
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Goff JS. The human sphincter of Oddi: physiology and pathophysiology. Arch Intern Med. 1988;148(12):2673-2677. doi:10.1001/archinte.1988.00380120115023
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Abdelwahab A, Zuchelli T. Anatomy, abdomen, and pelvis, sphincter of Oddi. StatPearls 2023. https://www.ncbi.nlm.nih.gov/books/NBK551515/
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