Jejunum
The jejunum ( empty intestine ; original Latin spelling ieiunum ) is the upper part of the small intestine . In humans, it makes up about 2 ⁄ 5 of the small intestine and, with a length of up to two meters, is the second longest of the three sections of the small intestine. It connects to the duodenum (duodenum) and goes into the ileum (ileum). It owes its German name “Leerdarm” to the fact that it is mostly empty after death. As in the rest of the small intestine, digestive processes and the absorption of food components ( carbohydrates , proteins , fats , vitamins , salts and water ) take place in the empty intestine . The “stomach growling” does not arise in the stomach, but is caused by air noises in the jejunum. This is why this part of the intestine is also known as the growl .
anatomy
The jejunum is placed in numerous loops and attached to the back of the abdominal wall with the mesentery . The corresponding section of the mesentery is called the mesojejunum ; In connection with the ileum following the jejunum , the suspension structure Radix mesenterii is called , which begins in the area of the duodenal- jejunum curvature ( flexura duodenojejunalis ) and ends at the ileocecal valve .
The jejunal loops are very mobile and therefore variable in their position. An exception are ruminants in which the jejunum surrounds the colon disc of the ascending colon ("coronary intestine") like a wreath and is fixed to it. In domestic cattle , the jejunum is up to 45 meters long.
While the beginning of the jejunum is clearly defined by the duodenojejunal flexura at the level of the second lumbar vertebral body, the boundary between jejunum and ileum cannot be sharply delimited anatomically . In animal anatomy, the end of the cecum-hip fold ( plica ileocecalis ) is used as the border.
Like all hollow organs, the empty intestine is lined with a mucous membrane ( tunica mucosa ). On the outside, there is a double layer of smooth muscles ( tunica muscularis ), the outer organ closure is formed by the serosa covering of the peritoneum .
The upper part of the radix mesenterii leads vessels of the arteria mesenterica superior to supply the jejunum, ileum , cecum , ascending colon and the first two thirds of the transverse colon . The jejunum is supplied with blood from the arteriae jejunales from the arteria mesenterica superior. The veins of the jejunum flow into the superior mesenteric vein , which runs to the right of the superior mesenteric artery, and then runs behind the head of the pancreas to the portal vein .
The neural control of the jejunum is mainly realized via the enteric nervous system . The peristalsis is regulated by the myenteric plexus (Auerbach plexus), the innervation of the mucous membrane by the submucosal plexus (Meissner plexus). In addition, the jejunum is regulated by the sympathetic and parasympathetic nerves (especially the vagus nerve ).
