The small intestine is part of the human digestive tract and is located between the stomach and the large intestine. It is where much of the actual digestion takes place. Many food components are absorbed there and can then be further utilized by the body.
What is the small intestine?
By the small intestine, physicians mean the middle part of the digestive tract, which is located between the stomach and the large intestine. It is divided into three parts and has a length of three to six meters in an adult human. Thus, the small intestine is the longest section of the digestive system. It has a particularly structured surface, which makes it possible to optimally absorb the dissolved food components. The task of the small intestine is to absorb and utilize the pre-dissolved food components that it receives from the stomach. In this process, the intestinal wall absorbs the nutrients and directs them to the liver, where they are further processed.
Anatomy and structure
The small intestine immediately follows the stomach in the human digestive system. It consists of the duodenum, the jejunum, and the ileum, with the jejunum making up the largest percentage of the small intestine. The inner surface of the intestinal walls is particularly enlarged in order to optimally absorb the nutrients obtained from food. This is achieved with the help of special folds, intestinal villi (elevations) and microvilli (surface-enlarging cell processes). In total, an average small intestine has an absorption surface of up to 180 m². The duodenum contains the so-called Brunner glands, which neutralize gastric acid. Food residues not utilized by the small intestine are passed on to the large intestine, where further digestion and storage until excretion takes place.
Functions and tasks
The small intestine is where food arrives after being predigested in the stomach. The small intestine is responsible for continuing digestion and for dissolving and absorbing nutrients from food. Digestion takes place through enzymes that are able to break down fats, carbohydrates and proteins into their components. These can then be absorbed by the specially designed intestinal wall and passed on to the liver for further utilization. For this purpose, the food pulp, known as chyme in technical terminology, is first neutralized in the duodenum – this is necessary because a certain amount of gastric acid was added to it in the stomach. In the further digestive process, the scrum has the function of absorbing and further utilizing vitamin B12. In addition, this section of the small intestine has an importance for the body’s immune defense that should not be underestimated. The entire small intestine reabsorbs about nine liters of fluid daily during these processes. This is obtained, among other things, from food or ingested fluid and from the body’s own secretions, such as those of the salivary glands. After the small intestine has extracted the nutrients from the food pulp, these are passed on to the liver. Remnants that cannot be utilized pass into the large intestine and are eventually excreted.
Diseases
Like all organs of the human body, the digestive tract, including the small intestine, can experience dysfunction or even disease. Most people suffer from diarrhea from time to time, but it is not a disease itself, but always just a symptom that something is wrong. One reason for persistent diarrhea or other intestinal complaints can be food intolerances such as gluten or lactose intolerance. Fungi, bacteria or parasites that infest the intestines can also cause unpleasant symptoms. One disease that can severely impair the functioning of the small intestine is Crohn’s disease, an inflammatory bowel disease that causes pain, vomiting and severe diarrhea, among other symptoms. Cancers of the small intestine can become life-threatening if they are not treated. These include duodenal ulcer, for example, but also other tumors in the area of the small intestine. Intestinal obstruction, also called ileus, can also cause a life-threatening condition. In most cases, immediate emergency surgery is performed here to save the patient’s life. If small bowel disease is suspected or if regular symptoms occur, a doctor should always be consulted to rule out a more serious illness.
Typical and common intestinal diseases
- Crohn’s disease (chronic inflammation of the intestine)
- Inflammation of the intestine (enteritis)
- Intestinal polyps
- Intestinal colic
- Diverticula in the intestine (diverticulosis)
