The jejunum ( jejunum ) is one of the three sections of the small intestine. It follows on from the duodenum ( duodenum) and goes into the ileum ( ileum ) over. He is in an adult human up to two meters long. His German name " jejunum " he owes to the fact that he usually is empty after death.
The jejunum is placed in numerous loops and attached to the mesentery to the dorsal abdominal wall. The relevant section of the mesentery is called Mesojejunum; in conjunction with the day following the jejunum ileum refers to the suspension structure root of the mesentery, which ( duodenojejunal flexure ) begins in the duodenum - jejunum curvature and ends at the ileocecal valve.
The Jejunumschlingen are very mobile and they are variable in position. An exception are ruminants, in which the jejunum coronary surrounds the Kolonscheibe the ascending colon ( " ring casing " ) and is fixed to this. In a domestic cattle the jejunum is up to 45 meters long.
While the beginning of the jejunum through the duodenojejunal flexure clearly defined at the level of the second lumbar vertebral body, the boundary between the jejunum and ileum can be anatomically not sharply defined. In animal anatomy, the end of the cecal Hüftdarm - fold ( plica ileocecalis ) is used as a border.
Like all hollow organs is lined with a mucous membrane ( tunica mucosa ) of the jejunum. Outwardly, is followed by a double layer of smooth muscle in (tunica muscularis ), the outer body concludes with the serosa of the peritoneum.
The upper part of the root of the mesentery leads vessels of the superior mesenteric artery for the supply of the jejunum, ileum, cecum, ascending colon and the first two thirds of the transverse colon. The blood supply of the jejunum is performed by the jejunales arteries from the superior mesenteric artery. The veins of the jejunum empty into the superior mesenteric vein, which runs to the right of the superior mesenteric artery, and then draw behind the head of the pancreas to the portal vein.
The neural control of the jejunum is realized mainly via the enteric nervous system. The regulation of peristalsis is done by the myenteric plexus ( Auerbach plexus ), the innervation of the mucous membrane by the submucosal plexus ( Meissner's plexus ). In addition, the jejunum of sympathetic and parasympathetic is (especially the vagus nerve ) controls.