Difference Between Ilium and Ileum

The key difference between ilium and ileum is that ilium is the uppermost part of the hip bone, while ileum is the last and longest part of the small intestine, located between the jejunum and cecum of the large intestine.

Ilium and ileum are two parts of our body. Although these two names are similar, they refer to two distinct structures. Ilium is a part of the hip bone while ileum is a part of the small intestine. In fact, the ilium is the widest and the uppermost part of the hip bone. On the other hand, the ileum is the last and the longest part of the small intestine.

CONTENTS

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

What is Ilium?

Ilium, also called iliac bone, is the largest part of the hip bone found in the vertebrates. Moreover, it is the uppermost of the three bones containing each half of the pelvis. Ilium forms the pelvic bone together with the ischium and pubis. It is fan-shaped in adults. It accounts for the width of the hips.

There are two major divisions: the body and the wing. The body of the ilium forms the superior part of the acetabulum. The wing part has two faces as inner surface and outer surface. The ilium serves a weight-bearing function. It also works as the structure that ensures the spine is supported when the body is upright.

What is Ileum?

The ileum is the last part of the small intestine located between the jejunum and large intestine. The ileum of the human small intestine is 2 – 4 m long. It has a neutral or slightly basic pH. Ileum absorbs nutrients that are not absorbed by the jejunum. It mainly absorbs vitamin B12 and bile salts. Ileocecal valve separates ileum from the cecum of the large intestine.

There is no clear demarcation between jejunum and ileum. But, ileum differs from jejunum by several factors. Firstly, the ileum has more fat inside the mesentery. Also, the diameter of the ileum lumen is smaller and the walls are thinner. Moreover, the circular folds are also smaller in the ileum. However, the last part of the ileum has no circular folds. Furthermore, ileum has abundant Peyer’s patches containing large numbers of lymphocytes and other immune cells.

When considering the wall of ileum, it has four layers: a mucous membrane, a submucosa, an external muscular layer and a serosa. Moreover, ileum has many tiny finger-like projections known as villi on its internal surface in order to increase the surface area for the absorption of nutrients. Furthermore, the cells of ileum lining are able to secrete protease and carbohydrase enzymes responsible for the final stages of protein and carbohydrate digestion.

What are the Similarities Between Ilium and Ileum?

• Ilium and ileum are two body parts found in vertebrates.
• Both carry out very important functions in our body.

What is the Difference Between Ilium and Ileum?

Ilium is one of the three parts of the hip bone, while ileum is a part of the small intestine. So, this is the key difference between ilium and ileum. Functionally, ilium provides structural support and protection, while ileum absorbs vitamin B12, bile salts and other nutrients. Therefore, this is also a difference between ilium and ileum. Moreover, the ilium is bony in nature, while ileum is soft in nature.

The below infographic summarizes the difference between ilium and ileum.

Summary – Ilium vs Ileum

Ilium is the uppermost of the three bones in the hipbone. In contrast, the ileum is the longest and final portion of the small intestine. So, this is the key difference between ilium and ileum. Ilium provides a structural and protective function. But, on the other hand, ileum absorbs vitamin B12, bile salts and other nutrients that were not absorbed by the jejunum. Moreover, the ilium is bony in nature, while ileum is soft in nature.

Reference:

1. Gurarie, Mark. “The Anatomy of the Ilium.” Verywell Health, Verywell Health, 30 Sept. 2019, Available here.
2. “Ileum.” Wikipedia, Wikimedia Foundation, 14 Aug. 2019, Available here.

Image Courtesy:

1. “Pelvis diagram” By Je at uwo at English Wikipedia – Transferred from en.wikipedia to Commons (Public Domain) via Commons Wikimedia
2. “Illu small intestine” Public Domain) via Commons Wikimedia