Root of the mesentery

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The root of the mesentery, or root of the small bowel mesentery to be exact, is the origin of the mesentery of the small intestine (i.e. jejunum and ileum) from the posterior parietal peritoneum., attached to the posterior abdominal wall. It descends from the duodenojejunal flexure at a 45 degree angle to the ileocecal junction in the right iliac fossa.

Gross anatomy

The mesenteric root lies along a line running diagonally from the duodenojejunal flexure to the right sacroiliac joint. It crosses over the third part of the duodenum, aorta, inferior vena cava, right ureter and right psoas major muscle. Its average length is 15 cm, while the intestinal attachment of the mesentery is the same length as the small intestine itself (around 3.5-5 m) and greatly folded.

The root of the mesentery divides the infracolic compartment into:

  • right (upper) infracolic space 
  • left (lower) infracolic space

It contains the superior mesenteric artery (SMA) and superior mesenteric vein (SMV).

Relations

The mesenteric root is contiguous