Jejunum vs ileum

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There are a few differences that can help differentiate jejunum and ileum:

  • location
    • jejunum: upper left part of the peritoneal cavity
    • ileum: lower right part of the peritoneal cavity
  • gross appearance
    • jejunum: greater caliber (<3 cm), thicker walls and more vascular 
    • ileum: lesser caliber (<2 cm), thinner walls and less vascular
  • interior
    • jejunal folds (valvulae conniventes) are thicker (2-3 mm) than ileal folds (1-2 mm)
    • jejunal folds are also more numerous and deeper than ileal folds
  • mesentery
    • jejunum: less fat, longer vasa recta, fewer arterial arcades
    • ileum: more fat, more arterial arcades, shorter vasa recta
  • immunology
    • presence of aggregated lymphoid follicles (Peyer patches), more prominent in the ileum