The intestine - our digestive organ

Here you will find explanations about the structure and function of the intestine, how a colonoscopy works and more information about intestinal diseases and colon cancer

Our content is pharmaceutically and medically tested

“Gut: Anatomy and Function

The human intestine is five to seven meters long and lined with a mucous membrane on the inside. This is laid in folds in different ways, so that there is a strong increase in surface area. This is important for the absorption of nutrients, the main task of the intestine. Different sections of the intestine have different tasks in this regard. Basically, a distinction is made between the intestines

  • Small intestine
  • and colon

These two parts can in turn be divided into different sections.

The food pulp from the stomach is transported in so-called persital waves through the tube system of the intestine. In a healthy bowel, this usually only happens in one direction: from the mouth to the anus. Due to the wave movement, the food pulp is further mixed at the same time. In the beginning this is still quite liquid, but the further the food travels through the intestine, the firmer it becomes.

The loops of the small intestine lie loosely in the middle, while the large intestine runs along the outside like a frame

© W & B / Dr. Ulrike Möhle

The small intestine

The small intestine can be divided into the following sections:

  • Duodenum (medical: duodenum)
  • Jejunum (medical: jejunum)
  • Ileum


The duodenum begins directly after the exit of the stomach and is C-shaped in the upper abdomen. It is about 25 to 30 centimeters long - this corresponds to about twelve finger widths. Hence this section of the intestine has its name. The ducts of the gallbladder and pancreas open into the duodenum. Here the chyme from the stomach is mixed with the digestive juices and the first nutrients are absorbed. In addition, the very acidic stomach contents in the duodenum are somewhat neutralized. The duodenum opens into the rest of the small intestine with a slight kink.

Venom and ileum

Empty intestine and ileum (jejunum and ileum) make up the longest part of the intestine: a total of up to five meters of small intestine loops lie loosely in the abdomen. This is where most of the nutrients from food are absorbed. In the jejunum these are above all

  • water-soluble vitamins
  • Fats (lipids)
  • Salts (electrolytes)
  • and amino acids

The ileum is responsible for receiving

  • water
  • vitamin C
  • Vitamin B12 (important for blood formation)
  • Bile acids

The ileum usually ends in the right lower abdomen with a valve (also called Bauhin’s valve) in the first section of the large intestine: the appendix. There is a higher density of bacteria in the large intestine than in the small intestine. The valve is designed to prevent intestinal contents (and therefore also many bacteria) from flowing back from the large intestine into the small intestine.


The large intestine is like a frame around the loops of the small intestine. It is less flexible than the small intestine. In the large intestine, different sections are also distinguished that have special tasks. The colon is made up of

  • Appendix (caecum) and appendix (appendix vermiformis)
  • Colon (colon)
  • and rectum (rectum with anal canal)

Appendix and appendix

Behind the valve there is a bulge in the intestine in the lower right abdomen: the appendix (ceacum). It represents the transition to the large intestine. At the caecum there is a small, finger-like appendix (appendix vermiformis). This appendix can become inflamed and cause major problems, which - incorrectly - are known as "appendicitis".

The appendix is ​​also known as the "intestinal almond" because there are many immune cells in its wall. If you remove it because of inflammation, there is no disadvantage.

Colon (colon)

After the appendix, the colon (colon) begins. This has the task of removing the remaining water from the pulp so that stool is formed from it.

The colon is divided according to its course in the abdomen. These are in the order in which the porridge passes through the sections

  • ascending colon
  • Transverse colon
  • descending colon
  • and S-shaped colon (Colon sigmoideon or Sigma)


At approximately the level of the sacrum, the sigma passes into the rectum. Together with the anal canal, this forms the rectum and ensures the continence of bowel movements and intestinal winds. In this area there are many muscle layers that have to work well together so that a bowel movement (defecation) occurs or so that the bowel movement can be held back.

The bowel movement

For many people a shame-ridden topic, but an inevitable, very natural process. A healthy intestinal flora and regular bowel movements have an impact on our health and well-being. On average, a healthy person excretes around 100 to 200 grams of stool per day. You can find more information about bowel movements here.