Editing Duodenum (section)

===Blood supply===
The first (superior) part of the duodenum, right after the [[pylorus]] of the stomach, is not supplied by the arcades. Instead, it is supplied by the [[supraduodenal artery]] and posterior superior pancreaticoduodenal artery, along with some branches of the [[right gastroepiploic artery]] and the anterior superior pancreaticoduodenal artery. In many people part of the first centimeter of the duodenum is also supplied by branches of the [[right gastric artery]].<ref name=":4">{{Cite journal |last=Androulakis |first=John |last2=Colborn |first2=Gene L. |last3=Skandalakis |first3=Panagiotis N. |last4=Skandalakis |first4=Lee J. |last5=Skandalakis |first5=John E. |date=2000-02-01 |title=EMBRYOLOGIC AND ANATOMIC BASIS OF DUODENAL SURGERY |url=https://linkinghub.elsevier.com/retrieve/pii/S0039610905704011 |journal=Surgical Clinics of North America |volume=80 |issue=1 |pages=171–199 |doi=10.1016/S0039-6109(05)70401-1 |issn=0039-6109}}</ref>

The remaining three parts (descending, horizontal, and ascending) of the duodenum are supplied by two arcades (rings) of arteries, one anterior (in front) of the duodenum and pancreas and one posterior to (behind) them. Each arcade is made of two [[Anastomosis|anastomosed]] (connected) arteries. The superior artery of each arcade comes from the [[superior pancreaticoduodenal artery]], which arises from the [[celiac artery]] via the [[gastroduodenal artery]]. The inferior artery of each arcade comes from the [[inferior pancreaticoduodenal artery]], a branch of the [[superior mesenteric artery]]. The anterior arcade is formed by the anterior superior pancreaticoduodenal artery and the anterior inferior pancreaticoduodenal artery; the posterior arcade is formed by the posterior superior pancreaticoduodenal artery and the posterior inferior pancreaticoduodenal artery.<ref name=":4" /><ref>{{Citation |last=Aasen |first=S. |title=Stomach Duodenum Normal Anatomy, Function and Congenital Anomalies |date=2013 |work=Abdominal Imaging |pages=367–382 |editor-last=Hamm |editor-first=Bernd |url=https://link.springer.com/referenceworkentry/10.1007/978-3-642-13327-5_17 |access-date=2025-03-09 |place=Berlin, Heidelberg |publisher=Springer |language=en |doi=10.1007/978-3-642-13327-5_17 |isbn=978-3-642-13327-5 |last2=Lundin |first2=K. E. A. |editor2-last=Ros |editor2-first=Pablo R.}}</ref> 

Vessels from the arcades supply the [[Muscular layer|muscularis externa]] (muscular layer) before forming a [[plexus]] (network of blood vessels) in the [[submucosa]] (a layer of connective tissue) called the [[submucosal plexus]]. Vessels continue from the submucosal plexus through the [[muscularis mucosae]] (another thin muscular layer) before forming another plexus under the [[epithelium]] of the [[Intestinal villus|villi]], the layer where nutrients are absorbed. These vessels entering the duodenum from the arcades are sometimes called [[Vasa recta (intestines)|vasae rectae]] or arteriae rectae.<ref name=":4" /> 

The venous drainage of the duodenum mainly follows the arteries, ultimately draining into the [[Portal venous system|portal system]]. The venous arcades are usually superficial to the arterial arcades. The anterior superior pancreaticoduodenal vein drains into the [[right gastroepiploic vein]], as do the veins of the lower first part of the duodenum and the pylorus (subpyloric veins). The upper first part of the duodenum is drained by suprapyloric veins, which can drain into the [[portal vein]] or the posterior superior pancreaticoduodenal vein, which drains into the portal vein. The inferior veins of the arcades drain into the [[Superior mesenteric vein|superior mesenteric]], [[Inferior mesenteric vein|inferior mesenteric]], [[Splenic vein|splenic]], or first [[Jejunal veins|jejunal vein]].<ref name=":4" />

Embryologically, the duodenum arises from both the [[foregut]] and [[midgut]], constituting the boundary between the two. However, the "midgut" is defined surgically as the parts of the intestine supplied by the superior mesenteric artery. Since the duodenum is supplied both by the [[celiac artery]] and the superior mesenteric artery, these two definitions are similar but not exactly the same.<ref name=":4" />