What is the Ileum?

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  • Written By: Archana Khambekar
  • Edited By: Andrew Jones
  • Last Modified Date: 30 August 2019
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The ileum is the end part of the small intestine. It is extends from the jejunum, the middle part of the small intestine, to the beginning of the to the large intestine. The absorption of vitamin B12 and bile salts are among its most important functions.

Located in the lower abdominal area, the ileum lies next to the duodenum and jejunum, which are the other two segments of the small intestine. In adult humans, the ileum is about 12 feet long and stretches up to the ileocecal valve, which connects to the large intestine. It is held in the abdominal cavity by a membrane called the mesentery, and receives blood supply from the superior mesenteric artery and the arterial branches.

The ileum performs some vital functions. It helps assimilate vitamin B12 through special receptors. Cells lining its wall secrete enzymes that facilitate further breakdown of proteins and carbohydrates. It is also the site of fluid and electrolyte absorption. The ileum reabsorbs bile salts and thus helps maintain an adequate level of bile salts for digestion and absorption of dietary fat in the small intestine.


The ileal wall is composed of smooth muscle, has a few folds in it, and typically is thinner than the wall of the jejunum. Its wall is lined with projecting structures called the villi and microvilli. The villi help take up nutrients that become available through the digestive process, and conduct them to the bloodstream and the liver. Peyer’s patches, which are bundles of lymphatic cells are located in the ileal lining. These cells may be involved in body’s immune mechanisms.

The unabsorbed remains from the digestive process pass on from the ileum to the large intestine. The content moves forward through slow muscular contractions or peristalsis. The ileocecal valve which links the small and large intestine keeps the undigested content from flowing back.

Certain disorders such as Crohn’s disease may affect the functioning of this part of the small intestine. Individuals afflicted with this condition could develop inflammation in the ileum. The condition may cause abdominal pain, diarrhea, and weight loss. One could develop a vitamin deficiency as the absorption of vitamin B12 in the small intestine is affected.

If the ileum is considerably damaged, the patient may be recommended for surgery to remove the diseased portion. One of the problems that could arise from this surgery is that reabsorption of bile acids in the small intestine is impaired. As a result, the patient may suffer from diarrhea.


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Discuss this Article

Post 7

I am replying to theknot: Twenty years ago I had the ileum valve removed as well as some of my small and large intestines. I did not have to have a bag and live a somewhat normal life. The only problem I have since valve removal is constantly having diarrhea. Running to the bathroom constantly. No need to be scared.

Post 6

I have Crohn's and have developed strictures. My surgeon informed me today that my ileum valve up to my jejunum needs to be removed. Has anyone else had this done? If so, what should I expect and will I need a bag, and if so, for how long? I am scared to death!

Post 5

The book "Physician Heal Thyself" by John Ruben or "The Maker's Diet" by John Ruben, as well as his website are great resources for Crohn's disease.

He had it, almost died from it, changed his lifestyle and is living healthy! Good luck!

Post 4

I have Crohn's disease and looking for answers on how to control it, so if anyone can help me please do.

Post 3

@amysamp - Like the article discussed Crohn's disease is a disease that involves the ileum but the specific ileum disease that is most commonly found with Crohn's disease is ileocolitis. This disease affects the valve between the ileum and the colon.

And as far as the cause of Crohn's disease? It is still unknown.

Post 2

The ileum is a part of the enzyme process! I was just reading about how important these enzymes are therefore our ileum seems rather important (unlike some of our other organs doctors seem to just remove like our appendix or gall bladder).

I saw in the article that part of your ileum may become diseased but what are some specific ileum diseases that one might have?

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