Ileum

The ileum is the final part of the small intestine, following the duodenum and jejunum.

Terminology

The ileum is not to be confused with the ilium - the associated plural/adjectival forms are ilea/ileal and ilia/ilial respectively.

Gross anatomy

The ileum is 2-4 m in length and is separated from the cecum by the ileocecal valve (ICV). While there is no discrete line demarcating the jejunum from the ileum, there are a few differences between the two:

  • ileal mesentery contains more fat than jejunal mesentery
  • ileum tends to be smaller caliber than jejunum
  • ileum tends to be lighter in color than the jejunum
  • ileum contains abundant Peyer patches
    • Peyer patches are unencapsulated lymphoid nodules that contain large amounts of lymphocytes and other cells of the immune system
    • Peyer patches are only found on the antimesenteric border

Arterial supply

Venous drainage

Lymphatic drainage

  • drain to superior mesenteric lymph nodes

Innervation

  • via superior mesenteric plexus
    • sympathetic supply from lateral horn cells of the T9-T10 spinal cord
    • parasympathetic supply from vagus nerves

Variant anatomy

Related pathology