What is the jejunum function

Small intestine - structure and function

The small intestine is about 5-6 meters long and is divided into 3 main sections:

  • Duodenum
  • Jejunum
  • Ileum

The duodenum is located in the upper abdomen and is about 30 centimeters long. The large digestive glands of liver, gall bladder and pancreas flow into it. In the lower abdomen are empty and ileum, which form many loops due to their length.


The food pulp is digested further in the small intestine and the nutrients obtained are absorbed. The food stays in the small intestine for many hours and thus comes into close contact with the digestive enzymes and the intestinal surface, which absorbs the nutrients.

In order to be able to absorb the nutrients even better, the mucous membrane of the small intestine is strongly folded. On the entire surface and the folds there are wart-shaped elevations, the intestinal villi, which increase the surface again. The surface of the intestine is 400-500 square meters. In the approximately 4 million villi, the nutrients are absorbed in the blood and lymph.

As in the stomach, rhythmic movements (peristalsis) in the small intestine ensure that the food is mixed and transported further.

Another important function is water absorption: in the small intestine, 80% of the water is withdrawn from the food pulp. As a result, it is strongly thickened. The remaining 20% ​​is absorbed by the large intestine. Of the up to 9 liters of water that are withdrawn from the pulp every day, about 7 liters come from gastric juice and 2 liters from the food itself.

At the same time, the small intestine is very rich in hormone-producing cells. This includes B. Serotonin, which increases the mobility of the muscle wall. Others act on the surrounding organs such as the pancreas, stomach and the production of bile.

The so-called intestinal-associated lymphatic tissue plays an important role in the defense against viruses, bacteria and harmful foreign substances. It consists of numerous individual lymph nodes in the mucous membrane.