Last revised by Daniel J Bell on 3 Mar 2023

The jejunum (plural: jejuna or jejunums) is the second part of the small intestine, following the duodenum and before the ileum.

  • location: peritoneal cavity

  • function: absorption of carbohydrates, amino acids and fatty acids

  • blood supply and drainage: jejunal branches of the superior mesenteric artery and vein

The jejunum measures on average 2.5 m in length 1. It is differentiated from the duodenum by the duodenal-jejunal flexure, however there is no discrete anatomical landmark differentiating it from the ileum.

Together with the ileum, the jejunum lies in the free margin of the mesentery as a continuation of the duodenum.

  • lymphatics drain into the superior mesenteric lymph nodes

Distension of the small bowel with enteric contrast is commonly used to improve assessment. An anti-spasmodic drug may also be administered during the examination.

CT enteroclysis and MR enteroclysis involve the administration of enteric contrast through a nasojejunal tube, while CT enterography and MR enterography require the patient to drink oral contrast material.

The jejunum has a delicate feathery appearance and is located in the left upper abdomen. It can be differentiated from ileum by having a greater caliber, thicker and more numerous folds (see: jejunum vs ileum).

Small bowel enteroclysis allows better demonstration of the mucosa, although it is not widely used due to its invasive nature.

The jejunum arises from the midgut, and is formed by all three germinal layers (endoderm, ectoderm and mesoderm). During week 6-10 of gestation, herniation of the midgut occurs, causing it to lie outside the peritoneal cavity. Subsequently, it rotates 270 degrees before it is returned to its final anatomical position 3. Abnormalities of this process are associated with intestinal malrotation.

Jejunum means "empty" in Latin 4.

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