The duodenum , in Latin duodenum , is the first short section of the small intestine . In humans, it is about 30 cm long, which corresponds to about twelve finger widths (hence the name). In humans, its shape corresponds to the appearance of a C, in quadruped mammals a horseshoe open to the front . It surrounds the head of the pancreas and is fused with the abdominal cavity on the back wall. The bile duct as well as the main duct and, if present, the additional duct of the pancreas open into the duodenum .
The initial part of the duodenum is called the superior pars in humans and the cranial pars in animals . It arises at the pylorus ("gatekeeper" of the stomach ), is connected to the liver via the hepatoduodenal ligament (see omentum minus ) and is the only section within the peritoneum (intraperitoneally). In humans, the pars superior is enlarged into a duodenal ampulla (clinically: duodenal bulb ) and the transition to the jejunum is fixed by the duodenal suspensor ligament . In ungulates , the pars cranialis is bent in an S-shape (flexura sigmoidea) and rises on the right abdominal wall to the hepatic portal .
The pars superior ends with a curve ( flexura duodeni superior or cranialis ), continues into the descending part (pars descendens) and from now on the remaining sections of the duodenum are secondary retroperitoneal in humans. In mammals, the initial part of the descending part has a shallow fold of the mucous membrane (plica longitudinalis duodeni) on which the papilla duodeni major (syn. Vater papilla ), an elevation with the common mouth of the ductus pancreaticus and the ductus choledochus , sits. The descending part moves downwards, where the duodenum turns again in the flexura duodeni inferior or caudalis . This lower part is also called the pars horizontalis , in animals the pars transversa . The duodenum now continues as an ascending part (pars ascendens) and merges into the jejunum at the flexura duodenojejunalis (duodenum- jejunum bend) .
In many cases, another duct from the pancreas (pancreas) can open into the minor duodenal papilla via the usual bile opening, the major duodenal papilla . This duct is called the accessorius pancreatic duct (syn. Santorini duct ).
Arterially the duodenum is supplied via the gastroduodenal artery (from the common hepatic artery from the celiac trunk ), which in its further course gives off the supraduodenal artery and the superior pancreaticoduodenal arteries anterior and posterior . The last two arteries in particular are responsible for most of the supply to the duodenum. These form anastomoses with vascular branches of the arteria pancreaticoduodenalis inferior , which originates from the arteria mesenterica superior .
The venous outflow from the superior pars occurs via the superior pancreaticoduodenal vein into the portal vein (vena portae hepatis) . The remaining part of the duodenum drains through the veins that accompany the arteries, which open either into the superior mesenteric vein or directly into the portal vein.
See small intestine
The duodenum shows the structure typical of all organs of the gastrointestinal tract. This is divided into the mucous membrane (tunica mucosa), tela submucosa , muscle layer ( tunica muscularis ) and tunica adventitia (retroperitoneal) or serosa (intraperitoneal).
The mucous membrane is divided from the inside (intestinal lumen) outwards into:
- Lamina epithelialis consists of highly prismatic epithelium , which mainly consists of enterocytes carrying microvilli . There are also goblet cells , Paneth cells , enteroendocrine cells and M cells .
- Lamina propria mucosae made of loose connective tissue with a lamina muscularis mucosae , a circularly arranged layer of smooth muscles that allows fine adjustment to the intestinal contents. It represents the border to the underlying tela submucosa.
The tela submucosa consists of loose connective tissue and serves as a shifting layer between the mucous membrane and the muscle layer. It also contains blood vessels , lymph vessels , the submucosal plexus and, as a special feature of the duodenum, so-called Brunner's glands ( Glandulae duodenales ).
The muscle layer is divided into an inner ring and an outer longitudinal muscle layer ( stratum circulare and stratum longitudinal ). The task of the muscles is to generate the intestinal peristalsis , whereby a contraction of the ring layer narrows the intestinal lumen and a contraction of the longitudinal layer shortens the intestine. Between the circular and longitudinal muscle layers, there are vessels and the nerve fibers of the myenteric plexus in a thin layer of connective tissue .
The examination of the duodenum usually takes place with a flexible endoscope , since tissue samples ( biopsies ) can be taken at the same time . This is called a duodenoscopy . Usually the stomach ( gastroduodenoscopy ) and the adjacent part of the small intestine ( duodenojejunoscopy ) are also examined. Using a duodenal probe , the duodenal contents can be diverted for the purpose of examining pathogens or for immobilization, or nutrition can be made possible by bypassing the chewing and swallowing apparatus and the stomach.
The duodenum is of particular medical importance due to the very common duodenal ulcer (ulcus duodeni). About 2% of the population will develop such an ulcer in their lifetime.
Other diseases are:
- Duodenal diverticulum
- Duodenal stenosis
- Duodenal atresia
- Duodenal tumors : duodenal carcinoma
- Duodenal compression z. B. in the superior mesenteric artery syndrome or the superior mesenteric vein syndrome
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