Organ
Jejunum
Proximal mobile bowel with prominent absorptive folds
High-yield
Compared with distal ileum, jejunum usually has fewer arterial arcades, longer straight vessels and less fat obscuring the mesenteric windows; the features change gradually along the bowel.
Overview
The jejunum begins where the duodenum turns at the duodenojejunal flexure. Its loops usually lie mainly in the upper left infracolic region, suspended by the mesentery. A relatively thick wall and prominent circular folds accompany its major role in absorption.
Reference facts
- Location
- Usually the more proximal, upper-left loops of mesenteric small intestine beyond the duodenojejunal flexure.
- Parts
- Transitions continuously into ileum; there is no sharp external boundary between them.
- Blood supply
- Jejunal SMA branches form relatively few arcade tiers and longer vasa recta compared with more distal small bowel.
- Innervation
- Superior mesenteric autonomic pathways with vagal parasympathetic input; local enteric circuits coordinate motility and secretion.
- Venous/Lymphatic drainage
- Jejunal veins drain into the superior mesenteric system; lymph passes through mesenteric nodes, and villous lacteals carry absorbed long-chain dietary lipids.
- Relations
- Loops lie within the colonic frame; the mesentery often contains translucent areas between vessels because fat is less extensive.
- Function
- A major region for absorption of digested carbohydrates, amino acids and lipids, with substantial absorption of water and electrolytes.
Clinical correlation
Circular mucosal folds can extend across the apparent width of a gas-filled small-bowel loop on radiographs. This helps distinguish bowel patterns, but fold visibility and distribution must be interpreted with the rest of the image.
Frequently asked questions
Where is the jejunum located?
Usually the more proximal, upper-left loops of mesenteric small intestine beyond the duodenojejunal flexure.
What does the jejunum do?
A major region for absorption of digested carbohydrates, amino acids and lipids, with substantial absorption of water and electrolytes.
What are the parts of the jejunum?
Transitions continuously into ileum; there is no sharp external boundary between them.
What is the blood supply of the jejunum?
The jejunum is supplied by the jejunal SMA branches form relatively few arcade tiers and longer vasa recta compared with more distal small bowel.