The coils of small bowel that lie mainly in the left upper abdomen, just beyond the point where the retroperitoneal part ends
Jejunum — it begins at the duodenojejunal flexure.
Anatomy · Organs & viscera
Jejunum
Upper two-fifths of the free small intestine
Left upper abdomen · small intestine
The jejunum is the middle section of the small intestine, running from the duodenojejunal flexure to the ileum. It makes up roughly the upper two-fifths of the mobile small bowel and lies mainly in the left upper part of the abdomen. Compared with the ileum it is wider, thicker-walled, redder and has larger, more tightly packed circular folds, and it does most of the absorption of nutrients.
How to spot them
- ▸Coils in the left upper abdomen (left upper quadrant and umbilical region), hanging on the mesentery
- ▸Wider (about 4 cm) and thicker-walled than the ileum, with a deeper red colour from its rich blood supply
- ▸Tall, closely spaced circular folds (plicae circulares) giving a feathery pattern on a barium follow-through
- ▸Mesentery with only one or two arterial arcades and long straight vessels (vasa recta), leaving translucent 'windows' with little fat
What to know
Its name comes from the Latin for 'fasting' because it was always found empty in dissection
Jejunum — from the Latin jejunus, 'empty' or 'fasting'.
The part of the small bowel with tall, tightly packed circular folds that give a feathery appearance on a barium film
The jejunum, with large plicae circulares (valvulae conniventes).
A section whose mesentery has long straight vessels and few arterial arcades, with clear windows between them
The jejunum — long vasa recta and one or two arcades.
Wider, thicker-walled and redder than the neighbouring coils that follow it
The jejunum compared with the ileum.
The part of the small bowel that does the bulk of nutrient absorption, with few of the aggregated lymphoid patches found further along
Jejunum — Peyer's patches are mainly found in the ileum instead.
It begins at a sharp bend suspended by the ligament of Treitz, at the left of the second lumbar vertebra
The jejunum starts at the duodenojejunal flexure.
Key ideas
- The jejunum's circular folds, villi and microvilli give it a huge absorptive surface for sugars, amino acids and fatty acids.
- The mesentery of the small bowel carries a fan of vessels from the superior mesenteric artery; branches to the jejunum form fewer arcades than those to the ileum.
Quick-fire facts
- •It makes up about two-fifths of the free small intestine; the ileum takes about three-fifths, but there is no sharp boundary between them.
- •The whole small intestine is about 3 to 5 m long in life and up to about 6 m after death, depending on the source.
- •The jejunum is about 4 cm wide; the ileum about 3 cm.
- •The jejunum has thicker walls and more prominent plicae circulares than the ileum.
- •Its blood supply comes from jejunal branches of the superior mesenteric artery.
- •The mesentery of the small intestine has a root about 15 cm long running from the duodenojejunal flexure to the right iliac fossa.
- •The jejunum is used for feeding tubes (jejunostomy) and for creating a Roux-en-Y limb in bypass surgery.
- •Coeliac disease characteristically flattens the villi of the duodenum and proximal jejunum.
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