What is the small intestine?

The small intestine is the longest part of the digestive system, about 7 meters long. It is a muscular tube that is divided into three portions: the duodenum, jejunum and ileum. The duodenum breaks down the food, while the jejunum and ileum absorb nutrients and send them into the bloodstream.

The small intestine flows into the large intestine through the ileocecal valve. It is a part of the gastrointestinal tract between the stomach and large intestine, where the digestion process and absorption of food takes place. The mucous membrane that covers the interior walls is covered by the intestinal villi (responsible for the absorption of nutrients introduced through food) and the circular folds, whose presence serves to expand the surface of the small intestine in order to better carry out tasks regarding digestion and absorption of nutrients.

The duodenum is the initial portion of the intestine. Being C-shaped and about 25 cm long, it extends from the end portion of the stomach to the duodenojejunal flexure, which is the border between the duodenum and the jejunum. The mucosal lining of the small intestine involves secretin (a hormone that stimulates the secretion of digestive juices) and serotonin (a neurotransmitter in the central nervous system) as well as the absorption of iron and calcium.

Fasting represents the second portion of the intestine. It is preceded by the ileum, from which it differs from in a few characteristics (thicker walls, more intestinal vili and circular folds). The ileum joints the cecum of the large intestine at the ileocecal junction.  

There are many ways that the small intestine can become diseased or problematic. A few problems with the small intestine can include Crohn’s disease, Celiac disease, Infections, Irritable Bowel syndrome, bleeding, Ulcers, Intestinal cancer and Intestinal obstruction. Seeking medical assistance is essential in order to verify the cause of the disorder, determine the most appropriate form of treatment and prevent symptoms from worsening. A healthy, balanced diet as well as bowel stimulant is often recommended as one of the best ways to keep the small intestine healthy and prevent complications from arising.


What function does the small intestine serve?

In general, the small intestine completes the digestion process that begins in the mouth and is continued throughout the stomach. Its primary function is to complete digestion by performing the action of the enteric juices, produced by the secretion of the Lieberkühn glands and absorb nutrients contained in food. In order to perform this function, the complex surface of the mucous membrane is extended by the presence of intestinal villi and circular folds.

The small intestine is where 90% of the digestion and absorption of food occurs, while the other 10% takes place in the stomach and large intestine. Digestion often involves two parts: the first is mechanical digestion and the second is chemical digestion. Mechanical digestion involves chewing, breaking up, and mixing of foods in the mouth, to be transferred to the stomach. Chemical digestion, on the other hand, uses enzymes, bile acids and others in order to break down food material and then absorb it into the tissues of the body.