This extends from the duodenojejunal junction but does not have an abrupt end, merging with the ileum distally.

Arteries:

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Derived from the jejunal branches of the superior mesenteric artery

Veins:

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Jejunum is drained by the jejunal veins that are tributaries of the superior mesenteric vein. The superior mesenteric vein  forms the portal vein with splenic vein.

Nerves:

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Parasympathetic fibers are through the vagi via the celiac plexus and the superior mesenteric plexus.

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Sympathetic fibers are from the thoracic splanchnic nerves.

 

Comparison between jejunum and ileum with reference to jejunum

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Jejunum  is about 4cm in diameter and hence larger than ileum which is about 3.5cm in diameter.

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It is thicker walled

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It is redder and therefore more vascularized

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Its mesentery has a few arterial arcades (1-2) with long branches.

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Its villi are larger

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Its circular folds are bigger

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Aggregated lymphatic follicles (Peyer’s patches) are absent or few in the  jejunal mucosa.

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Circular folds can be felt through the wall of the jejunum like a shirt sleeve under a coat

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Jejunum lies in the paraumbilical area.

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Mesentery of jejunum is thicker walled

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Mesentery of jejunum has more fat.

Relations of the jejunum

It is related anteriorly to the anterior abdominal wall, with the lesser omentum intervening. Posteriorly it lies on the posterior parietal peritoneum and all retroperitoneal structures.

 

 

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