Duodeni

Duodeni is a term that may appear in Latin anatomical text as the genitive singular of duodenum (duodeni = “of the duodenum”). In modern English, the standard term is duodenum, and the Latin plural form is usually duodena. The following description concerns the duodenum, the first portion of the small intestine.

The duodenum is the initial segment of the small intestine, typically about 25 to 30 centimeters long, forming a J- or C-shaped loop that partly encircles the head of the pancreas. It begins at the pylorus of the stomach and extends to the duodenojejunal flexure, and it is conventionally divided into four parts: superior, descending, horizontal, and ascending.

The descending part contains the major duodenal papilla, where the common bile duct and main pancreatic duct usually drain; the minor papilla is located in the second part for the accessory pancreatic duct. The first part is intraperitoneal, while the remaining parts are largely retroperitoneal and related to the pancreas, liver, and biliary tract.

Vascular supply arises from the gastroduodenal and superior pancreaticoduodenal arteries proximally, with distal supply from the inferior pancreaticoduodenal arteries, which arise from the superior mesenteric artery. Venous drainage generally parallels the arterial supply. Innervation is provided by parasympathetic fibers from the vagus nerve and sympathetic fibers from the celiac and superior mesenteric plexuses.

Histologically, the duodenum features mucosa with villi and microvilli, Brunner’s glands in the submucosa, and circular folds that aid digestion. Functionally, it neutralizes gastric acid, mixes chyme with bile and pancreatic juice, initiates digestion, and absorbs iron, calcium, and other nutrients.

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