The ileum is the last section of the small intestine and about three feet long. Read more about its structure and functions here!


The ileum (Cecum) is the last section of the small intestine after the jejunum (jejunum). With a length of about three meters, it accounts for three-fifths of the entire small intestine. In the ileum - as in the rest of the small intestine - digestive processes take place and also the absorption of water and bile acids. Read all about the ileum!

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  • What is the ileum?

  • What is the function of the ileum?

  • What problems can the ileum cause?

What is the ileum?

The ileum (crural intestine) covers approximately the last three meters of the total of five to six meters long small intestine. It starts after the jejunum (jejunum), but it is not clearly differentiated from it.

The ileum, like the jejunum, is attached to the posterior abdominal wall with the mesentery and winds in numerous freely movable loops to the lower right in the lower abdomen. There, the ileum ends with the Bauhin's flap, which represents the transition into the large intestine (more precisely in the cecum = cecum).

The wall of the ileum is basically the same as that in the rest of the small intestine. However, it is less thick and has fewer mucosal folds (Kerckring wrinkles) and villi - the inner surface and thus the resorption surface is not so much enlarged as in the jejunum. This is not necessary, because most of the usable food components in the duodenum and jejunum are absorbed into the blood.

For this, the ileum has more lymphoid follicles (Peyer's plaques), which are intended to ward off germs ingested with food.

What is the function of the ileum?

The ileum, like the rest of the small intestine, is involved in the absorption of nutrients, albeit to a lesser extent. In the ileum, those substances that could not be resorbed in the duodenum and jejunum are taken up: electrolytes, vitamins and trace elements.

In the terminal ileum (the last ten to 15 centimeters of the ileum), the reabsorption of bile acids, which are produced by the liver and packed in bile into the duodenum for fat digestion, takes place. After reabsorption of the bile acids, they return to the liver via the blood (enterohepatic circulation).

In addition, cobalamin (vitamin B12) is absorbed from the food in the terminal ileum.

The ileum also absorbs much of the water that is ingested with food, as well as any digestive secretions that are secreted into the stomach and small intestine. The rest is taken in the colon.

Meckel's diverticulum

In about two percent of all people, the ileum has a finger-shaped protuberance of the intestinal wall, about 60 centimeters in front of the Bauhin flap. This so-called Meckel's diverticulum is the remainder of the embryonic vitelline duct that led from the intestine to the navel.

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What problems can the ileum cause?

Crohn's disease is a chronic inflammatory bowel disease that can occur in both the colon and small intestine. In about 30 percent of the patients only the ileum is affected.

In intestinal obstruction, the food pulp in the intestine can no longer be transported - either due to a mechanical obstacle (mechanical ileus) or a paralysis of the intestine (paralytic ileus). About two thirds of all intestinal obstructions affect the small intestine.

Celiac disease is a genetic intolerance to gluten, the glue protein in cereals. The immune system of those affected reacts hypersensitive to gluten with chronic inflammation and destruction of the villi in the small intestine.

A vitamin B12 deficiency can cause anemia (pernicious anemia). It is caused by a resorption disorder in the terminal ileumthat can be caused by inflammation or medication.

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