Ileum
It forms the final segment of the small intestine in most vertebrates. The duodenum and jejunum of the small intestine are followed by the ileum. The ileum and the caecum are separated by the ICV (ileocecal valve). Its main role is to absorb bile salts, vitamin B12 and other digestive products that were left unabsorbed by the jejunum.
The ileum of humans is 2-4 m long, and it has a pH between 7 to 8. The ileum is found in most higher vertebrates, including reptiles, birds and mammals. In some fishes, the segments of the small intestine and the structure of the ileum is not clear.
Ilium
The ilium is the uppermost portion of the hip bone seen in most vertebrates. In humans, the ilium is composed of two parts, namely the wing and the body. The acetabulum of the pelvis is made of the ischium, and less than 2/5th structure is covered by the body of the ilium. The ilium forms the upper boundary, and the ischium forms the side and lower boundaries of the acetabulum. The wing of ilium is laterally bound to the greater pelvis.
It is seen in most birds, reptiles and mammals. It is not found in bony fishes and snakes. Although, some snakes have tiny bone structures that are similar to the ilium.
Also Read: Pelvic Girdle
Difference between Ileum and Ilium
| Ileum | Ilium |
|---|---|
| It is the final segment of the small intestine in most vertebrates | The ilium is the uppermost portion of the hip bone seen in most vertebrates. |
| It is a soft muscular structure that is a part of the digestive system. | It is a hard bony structure that is a part of the skeletal system. |
| It is a part of the small intestine. | It is a part of the pelvic girdle. |
| The ileum, along with the duodenum and jejunum, forms the small intestine. | The ilium, along with ischium and pubis, forms the pelvic girdle. |
| Its main role is to absorb bile salts, vitamin B12 and other digestive products that were left unabsorbed by the jejunum. | It acts as a structural support that performs the weight-bearing function. |
Extended Reading: Difference between Small Intestine and Large Intestine
Frequently Asked Questions
What is a pelvic girdle?
The pelvis is a region between the thighs and abdomen. The pelvic bone or pelvic girdle is composed of the ischium, ilium and pubis. Only during puberty these three structures fuse to form a single bone. Before that, they are just joined by y-shaped triradiate cartilage. The pelvic bone also has other structures like the sacrum, acetabulum and coccyx.
What is the ileocecal valve?
It is a sphincter muscle that separates the large and the small intestine. It is a junction between the ileum of the small intestine and the caecum of the large intestine. It has a papillose structure.
How does ileum help in the digestion process?
The ileum has small microvilli that increase the surface area for absorption. The lacteals in the villi help to absorb glycerol and fatty acids. It also secretes enzymes like carbohydrase and protease that help in the digestion of carbohydrates and proteins, respectively. It also secretes other hormones like secretin, gastrin and cholecystokinin into the blood.
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