Difference Between Jejunum and Ileum

Jejunum vs Ileum

The small intestine is made up of three parts including duodenum, jejunum, and ileum. Duodenum is the first part followed by jejunum and ileum. Jejunum and ileum lie in the middle of the abdominal cavity framed by the large intestine. There is no such natural line of separation to distinguish jejunum and ileum. There are, however, some subtle differences between these two parts. Both jejunum and ileum have slightly alkaline or neutral inner surface, and are important in absorbing nutrients from the digested products. These two portions together are approximately 6.5 m in length, ileum comprising three-fifths while jejunum comprising the rest (two-fifths). Also, both portions contain mesenteries, which initiate bowel mobility; hence it helps to move foods along the intestinal tract by the process called peristalsis.


Jejunum is the middle portion of the small intestine and lies between the duodenum and ileum. It starts at the duodenojejunal flexure on the left side of the second lumbar vertebra. In an adult human, it is approximately 2.5 m in length and 2.5 cm in diameter. Jejunum has thicker walls with more villi and plicae circulares when compared to ileum.


Ileum is the last part of the small intestine. It is approximately 2 to 4 m long and 2 cm wide and is separated from the cecum by the ileocecal valve. Illum is thin walled with narrower lumen. It mainly absorbs vitamin B12 and bile salt. Unlike the jejunum, ileum has more lymphatic follicles, which are important for mounting an immune response to antigens.

What is the difference between Jejunum and Ileum?

• Jejunum makes the middle part while ileum makes the last part of the small intestine.

• Jejunum is in the upper abdomen, to the left of the midline, whereas ileum is in the lower part of the abdomen and pelvis.

• Jejunum is wider than the ileum.

• Jejunum has little fat in the mesentery than ileum.

• The lumen of jejunum is wider than that of ileum.

• The inner surface of jejunum has numerous transverse folds while ileum has very few. Because of that, jejunum is thick walled while ileum is thin walled.

• Jejunum has longer vasa recta whereas, ileum has shorter vasa recta.

• Jejunum has little fat inside the mesentery than ileum. Therefore, the visibility of the vessels of jejunum is more accounting for peritoneal windows than ileum.

• Unlike the jejunum, ileum has more Payers’ patches, solitary and aggregated lymph nodes, and other cells of the immune system.

• Ileum mainly absorb vitamin B12, bile salt, and whatever the products of digestion that were not previously absorbed by jejunum, whereas jejunum absorb monosaccharides and amino acids.

• Jejunum has simpler blood supply, whereas ileum wall contains more arterial branches to supply more blood.