- The jejunum is one of the three sections of the small intestine. It follows the duodenum and transitions into the ileum.
It owes its German name Leerdarm to the fact that it is usually empty after death.*
The jejunum is arranged in numerous loops and attached to the posterior 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 is called the radix mesenterii, which begins in the area of the duodenojejunal flexure (Flexura duodenojejunalis) and ends at the ileocecal valve.
- The jejunal loops are very mobile and thus variable in their position. While the beginning of the jejunum is clearly defined by the duodenojejunal flexure at the level of the second lumbar vertebral body, the boundary between jejunum and ileum cannot be sharply delimited anatomically.
Like all hollow organs, the jejunum is lined with a mucous membrane (Tunica mucosa). Outwardly, it is followed by a double layer of smooth muscle (Tunica muscularis), and the outer organ closure is formed by the serosal covering of the peritoneum.
- The upper part of the radix mesenterii carries vessels of the superior mesenteric artery to supply the jejunum, ileum, cecum, ascending colon, and the first two-thirds of the transverse colon.
- The blood supply of the jejunum is provided by the jejunal arteries from the superior mesenteric artery. The veins of the jejunum drain into the superior mesenteric vein, which runs to the right of the superior mesenteric artery, then passes behind the head of the pancreas to the portal vein.
- The nervous control of the jejunum is primarily realized via the enteric nervous system. The regulation of peristalsis is carried out by the myenteric plexus (Auerbach's plexus), the innervation of the mucous membrane by the submucosal plexus (Meissner's plexus). In addition, the jejunum is regulated by the sympathetic and parasympathetic nervous systems (specifically the vagus nerve).
from lat. ieiunus: fasting, hungry, lean *