Last revised by Dr Daniel J Bell on 29 Apr 2021

The jejunum (plural: jejuna or jejunums) is arbitrarily defined as the proximal two-fifths of the small intestine and is, on average, about 3 m in length.

Compared to the ileum, the jejunum has more valvulae conniventes and fewer folds per unit length. Like the ileum, the normal jejunal wall thickness is less than 3 mm. The jejunum has a larger diameter compared to the ileum.

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

  • jejunal branches from the superior mesenteric artery
  • corresponding veins which drain into the superior mesenteric vein
  • lymphatics drain into the superior mesenteric lymph nodes
  • sympathetic: lateral horn cells of spinal segments T9 and T10
  • parasympathetic: vagus nerve augments the peristaltic activity

Jejunum has a delicate feathery appearance and is located in the left upper abdomen.

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