Mesenteric portion of small intestine in the lower abdomen, its length is 4-6 m, diameter - 2-4 cm proximal small intestine called the jejunum (jejunum), is about 2 / 5 and with no visible border passes in the ileum (ileum), which is in the right iliac fossa at the level of IV lumbar vertebra open in the initial division of the colon called the cecum.
This part of the small bowel mesentery is retained (mesenterium), a broad fold of peritoneum, consisting of two sheets. One edge of the mesentery attached to the rear of the abdomen and the other covers the small intestine, keeping it in limbo.
The walls of the jejunum and ileum have the same structure as the duodenum. The outer layer is formed by the serous membrane, and mucous membrane is lined with single-layered prismatic epithelium with striated border. It forms a roughly circular cross-folds 700-900 (plicae circulares) covered by intestinal villi (villi intestinales) in an amount of 4-5 million, which are more slender and shorter than twelve villi of the duodenum . In the thick mucosal lymph follicles are (folliculi lymphatici), representing an accumulation of lymphatic tissue. In the submucosa are blood vessels and nerves, the so-called Meissner plexus, and between the inner circular and outer longitudinal muscle layers is another plexus - auerbahovskoe.
|In Fig. 164.
The mucosa of the small intestine
1 - mucous membrane of the small intestine;
2 - submucosa;
3 - muscle membrane;
4 - lymph follicles;
5 - mesentery;
6 - circular transverse folds
a., aa. — arteria, arteriae (artery, the artery)
lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)
m., mm. — musculus, musculi (muscle, the muscle)
n., nn. — nervus, nervi (nerve, the nerve)
r., rr. — ramus, rami (branch)
s. — seu (or)
v., vv. — vena, venae (vienna)