Difference Between Jejunum and Ileum

The key difference between jejunum and ileum is that jejunum is the middle part of the small intestine which lies in between duodenum and ileum while ileum is the final part of the small intestine which lies in between jejunum and caecum.

The small intestine constitutes of three parts: 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 natural line of separation to distinguish jejunum and ileum. However, there is a subtle difference between jejunum and ileum. Both jejunum and ileum have a 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). Moreover, both portions contain mesenteries, which initiate bowel mobility; hence, it helps to move foods along the intestinal tract by a process called peristalsis.

CONTENTS

1. Overview and Key Difference
2. What is Jejunum 
3. What is Ileum
4. Similarities Between Jejunum and Ileum
5. Side by Side Comparison – Jejunum vs Ileum in Tabular Form
6. Summary

What is Jejunum?

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 the ileum.

What is Ileum?

Ileum is the last and lengthiest part of the small intestine located between jejunum and caecum. It is approximately 2 to 4 m long and 2 cm wide.  Ileocecal valve separates ileum from the caecum.  Illum is thin-walled with a narrower lumen. It mainly absorbs vitamin B12 and bile salt.

Figure 01: Jejunum and Ileum

Unlike the jejunum, ileum has more lymphatic follicles, which are important for mounting an immune response to antigens.

What are the Similarities Between Jejunum and Ileum?

• Jejunum and ileum are two parts of the small intestine.
• They are greatly coiled parts of the small intestine.
• Moreover, they are situated in the middle of the abdominal cavity framed by the large intestine.
• Both jejunum and ileum have slightly alkaline or neutral inner surface.
• They are important in absorbing nutrients from the digested products.

What is the Difference Between Jejunum and Ileum?

Jejunum is the middle part of the small intestine that is located in between duodenum and ileum while ileum is the final part of the small intestine which lies in between jejunum and caecum. Thus, this is the key difference between jejunum and ileum. Jejunum is in the upper abdomen, to the left of the midline, whereas ileum is in the lower part of the abdomen and pelvis. Thus, this is also a difference between jejunum and ileum. Structurally, jejunum is wider than the ileum. It also has little fat in the mesentery than ileum.

In addition, the inner surface of jejunum has numerous transverse folds, while ileum has very few. Moreover, jejunum is thick-walled while ileum is thin-walled. Another difference between jejunum and ileum is that ileum mainly absorb vitamin B12, bile salt, and whatever the products of digestion that were not previously absorbed by jejunum, whereas jejunum absorbs monosaccharides and amino acids. Jejunum has a simpler blood supply, whereas ileum wall contains more arterial branches to supply more blood. This is another difference between jejunum and ileum.

Summary – Jejunum vs Ileum

Jejunum and ileum are two parts of the small intestine. Jejunum is the middle part, while ileum is the last part. In addition, jejunum mainly absorbs monosaccharides and amino acids; in contrast, ileum mainly absorbs vitamin B12, bile salts and the nutrients that were not absorbed by the jejunum. Furthermore, jejunum has numerous transverse folds, while ileum has few. Jejunum is wider than the ileum, and the lumen of jejunum is wider than the ileum. Moreover, jejunum has a thick wall while ileum has a thin wall. This summarizes the difference between jejunum and ileum.

Reference:

1. “Boundless Anatomy and Physiology.” Lumen, Available here.

Image Courtesy:

1. “Blausen 0817 SmallIntestine Anatomy” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia

ncG1vNJzZmivp6x7pbXFn5yrnZ6YsqOx07CcnqZemLyue8OinZ%2Bdopq7pLGMm5ytr5Wau262xKOsp62dYq6vsIyvqmahnJrCrns%3D