Jejunum and ileum are collectively called small intestine, which is 3 ~ 5m long. The ileum is 3/5 of the distal segment of the small intestine, located at the lower right of the abdominal cavity, and part of the ileum is still in the pelvic cavity. The wall of the small intestine is wrapped by serosa, and the muscle layer is below the serosa. The arrangement direction of muscle fibers is the outer longitudinal row and the inner circular row. The muscular layer in the proximal segment is thicker, the distal segment gradually becomes thinner, and the near ileocecal part is thicker. The mucosal layer relaxes and forms annular folds (Figure 7. 10. 10 1).
The mesenteric root starts from 1 left or second lumbar vertebra, inclines to the lower right and ends in front of the right sacroiliac joint. The total length is about 15cm. The mesentery and its roots are composed of two layers of peritoneum, which contain blood vessels, nerves and lymphoid tissues. Because the length of the small intestine greatly exceeds the length of the mesenteric root, and the distance between the mesenteric root and the intestinal tube is long in the middle and short at both ends, the mesentery is fan-shaped and folded in many places. The mesentery is characterized by abundant adipose tissue and small and dense vascular arch.
See the encyclopedia entry: ileum [last revised at 2016/3/18:17:13 * * 911], and it is automatically matched.