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Anatomy of the Small Intestine

The small intestine is a tube measuring about 2.5 cm in diameter. The complete small intestine is approximately 600 cm (20 feet) long and coiled in loops, which fill most of the abdominal cavity. It extends from the pyloric sphincter to the ileocecal valve, where it joins the large intestine and is comprised of three parts:

  • Duodenum
    Approximately 25 cm long; proximal end of small intestine; joined to stomach by the pyloric sphincter.
  • Jejunum
    Approximately 200 cm long.
  • Ileum
    Approximately 300 cm long; joins the cecum at the ileocecal valve.

Peyer patches

Lymphoid tissue in lamina propria primarily in distal ileum; primary site for lymphomas.

Meckel diverticulum

Congenital anomaly of the ileum, a diverticulum analogous to the appendix of the cecum; a potential site for malignancy.

Anatomy of the Small Intestine

Illustration of the small intestine.