Role and function of the small intestine – the small intestine moves the intestinal contents towards the colon by means of peristaltic movement (motility).
It forms an important boundary layer between the bacteria in the intestinal contents and the sterile interior of the body (barrier function), in which both bowel movements and the production of immunoglobulins by the mucosa play a part.
The small intestinehas the important tasks of digestion, absorbing nutrients and secreting intestinal juice. Most carbohydrates, fats and proteins are absorbed in the first part of the small intestine(mainly in the jejunum).
Calcium, iron and folic acid are absorbed in the duodenum, while the final section of the ileum (terminal ileum) is responsible for absorbing vitamin B12 and bile acids. The small intestinealso produces proteins (apolipoproteins) that play an important role in fat transport.
It also produces hormone-like substances (bioamines, peptides).
