Small bowel mesentery
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The small bowel mesentery is a broad fan-shaped fold of peritoneum connecting the loops of jejunum and ileum to the posterior abdominal wall and is one of the four mesenteries in the abdominal cavity.
It is connected to the posterior abdominal wall by its root which measures about 15 cm and extends obliquely from the duodenojejunal flexure on the left of the second lumbar vertebra to the right lower quadrant anterior to the upper part of the right sacroiliac joint.
The root is a bare area continuous with the left anterior pararenal space superiorly, and the right anterior pararenal space inferiorly. In its course, it passes from left to right, successively in front of the horizontal part of the duodenum (where the superior mesenteric vessels enter the mesentery), the abdominal aorta, the inferior vena cava, the right ureter and the right psoas muscle. It suspends 6-8 meters of small bowel.
The intestinal border of the mesentery is characteristically thrown into a number of pleats or frills. The mesentery consists of two layers of peritoneum between which lie the jejunal and ileal branches of the superior mesenteric arteries and their accompanying veins, nerves and lymphatics.