The main function of the small intestine is the absorption of water, minerals and vitamins as well as the cleavage products of complex carbohydrates (starch), fats and protein This happens under the influence of bile and the digestive enzymes from the pancreas. The anatomy of the small intestine creates the ideal conditions for this by increasing the surface area by a factor of about 600 due to the presence of mucous membrane folds and intestinal villi (bulges).
Diseases of the small intestine
Diseases of the small intestine will consequently impair the utilization of nutrients. Other causes are insufficient production of bile salts and digestive enzymes from the pancreas. All these nutrient utilization disorders are grouped together under the generic term malassimilation.
If the cause of this disorder is insufficient digestion of nutrients, it is called maldigestion or digestive insufficiency. If the cause is an insufficient absorption of the nutrients by the intestinal mucosa, it is called malabsorption or absorption insufficiency. Normally, the absorption of nutrients is already completed in the upper sections of the small intestine.
However, if a part of the lower small intestine is removed surgically, the so-called short bowel syndrome occurs with, depending on the length of the missing intestinal sections, an insufficient supply of nutrients to the patient. In the last section of the small intestine (terminal ileum), vitamin B12 and the bile salts are absorbed. If this section of the intestine is missing, the result is a vitamin B12 deficiency, but this can easily be corrected by injecting the vitamin into the muscle.
The increased transfer of bile salts into the large intestine can cause diarrhoea and there is also a loss of bile salts with the stool. This leads to a decrease in the concentration of bile acid in the bile and disrupts fat digestion and consequently the absorption of fat-soluble vitamins. The small intestine also plays an important role as an immune organ and has a barrier function for germs in the intestine.
