Root of the mesentery and its course
Fixation of the mesentery to the posterior abdominal wall is achieved via its root (radix mesenterii). It originates at the level of the second lumbar vertebra (L2) on the left side in the region of the flexura duodenojejunalis. From this point, the root runs obliquely — from top to bottom and from left to right, ending in the right iliac fossa. The total length of the root is 15 to 23 cm.
Topographic relationships
Along its attachment, the root of the mesentery sequentially crosses several vital anatomical structures on the anterior surface of the posterior abdominal wall:
- Terminal part of the duodenum.
- Abdominal aorta.
- Inferior vena cava.
- Right ureter.
- Psoas major muscle (m. psoas).
Internal structure
Between the peritoneal layers forming the mesentery, within the adipose tissue, lies a complex of neurovascular structures. These include the superior mesenteric artery and its branches, corresponding veins, nerve plexuses, as well as lymphatic vessels and nodes.
Dimensions and width of the mesentery
The width of the mesentery is measured as the distance from its root to the attachment site at the intestinal wall. This parameter varies significantly across different segments:
- In the initial segment of the jejunum, the width is minimal, measuring only 1–2 cm.
- In the middle parts, the mesentery gradually widens to 13–17 cm.
- The width reaches its maximum values (20–25 cm) in the lower parts of the ileum.
- At the site of the transition of the intestine into the cecum, the width of the mesentery sharply decreases and tapers to nothing.
Briefly: answers to topical questions
What specific arterial branches pass in the mesentery to the jejunum and ileum?
Branches arise within the thickness of the mesentery to the jejunum and ileum from the convex surface of the superior mesenteric artery, directed to the left. These include branches for the small intestine: jejunal and ileal arteries (aa. jejunales et aa. ileales).
Straight arteries depart from the "parallel" vessel toward the mesenteric border of the intestine; each such vessel supplies a restricted area.
What groups of lymph nodes are distinguished in the mesentery of the small intestine?
Three rows of lymph nodes are distinguished in the mesentery of the small intestine. They are located as follows:
- First row — along the mesenteric border of the intestine.
- Second row — at the level of the intermediate vascular arcades.
- Third row — along the course of the main branches of the superior mesenteric artery.
Some lymphatic vessels may bypass these nodes and empty directly into the thoracic duct.
How is the root of the mesentery projected onto the anterior abdominal wall?
The root of the mesentery (radix mesenterii) has an oblique direction from top to bottom and from left to right. Its projection is defined by the following anatomical landmarks:
- Origin — located on the left at the level of the second lumbar vertebra (L2), at the duodenojejunal flexure (flexura duodenojejunalis).
- Termination — reaches the right iliac fossa.
The total length of the root is 15–23 cm.
Into which large vein does blood drain from the corresponding veins of the small intestine mesentery?
Blood from the veins of the small intestine mesentery collects into the superior mesenteric vein (v. mesenterica superior). It is formed by straight veins passing into the venous system of the jejunum and ileum. Having passed in the root of the mesentery, the superior mesenteric vein merges with the splenic vein (v. lienalis), resulting in the formation of the portal vein.
The root of the mesentery runs from L2 on the left to the right iliac fossa, crossing along the way "the aorta, vein, ureter, and psoas muscle".
Class and exam questions
Where does the root of the small intestine mesentery begin?
The root of the mesentery (radix mesenterii) begins at the level of the second lumbar vertebra (L2) on the left, in the region of the duodenojejunal flexure (flexura duodenojejunalis).
Which anatomical structures does the root of the mesentery cross anteriorly?
The root of the mesentery crosses the terminal part of the duodenum, the abdominal aorta, the inferior vena cava, the right ureter, and the psoas major muscle (m. psoas).
How does the width of the mesentery change from the jejunum to the ileum?
The width of the mesentery increases from 1–2 cm in the initial part of the jejunum to a maximum of 20–25 cm in the lower parts of the ileum, and tapers to nothing at the site of transition into the cecum.
What else to study on this topic
- Branches of the superior mesenteric artery in the mesentery
- Lymphatic system of the small intestine mesentery
- Features of the structure of the peritoneal folds
- Projection of the root of the mesentery onto the anterior abdominal wall
- Cellular spaces of the root of the mesentery
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