Gut & IBS
Learn about the structure and function of the bowel, how a colonoscopy works, and other interesting facts about bowel disease and Irritable Bowel Syndrome.


Gut / Bowel: Anatomy and Function

Gut overview & function

The human intestine is five to seven meters long and is lined on the inside with mucous membrane. This is folded in a variety of ways, resulting in a large increase in surface area. This is important for nutrient absorption, the main function of the intestine. Different parts of the intestine have different functions. The intestine is basically divided into

  • small intestine

  • and large intestine

These two parts can be divided into different sections.

The food pulp from the stomach is transported through the intestinal tube system in so-called persitaltic waves. In a healthy intestine, this usually happens in only one direction: from the mouth to the anus. At the same time, the wave motion mixes the food further. At first, this is quite liquid, but the further the food travels through the intestine, the more solid it becomes.

The Small Intestine

The small intestine is divided into the following sections:

  • Duodenum (medical term: duodenum)

  • Oblong intestine (medical term: jejunum)

  • Crooked intestine (medical term: ileum)


The duodenum begins just after the stomach leaves the body and lies in a C-shape in the upper abdomen. It is about 25 to 30 centimeters long - the width of about twelve fingers. This is where it gets its name. The ducts of the gallbladder and pancreas open into the duodenum. This is where the food from the stomach mixes with the digestive juices and the first nutrients are absorbed. In addition, the very acidic stomach contents are somewhat neutralized in the duodenum. The duodenum opens with a slight bend into the rest of the small intestine.

Jejunum and ileum

The jejunum and ileum make up the longest part of the intestine: In all, up to five feet of loops of small intestine lie loosely in the abdominal cavity. Most of the nutrients from food are absorbed in this part of the intestine. In the jejunum, these are mainly

  • Water-soluble vitamins

  • Fats (lipids)

  • Salts (electrolytes)

  • and amino acids

The ileum is responsible for the absorption of

  • Water

  • Vitamin C

  • Vitamin B12 (important for hematopoiesis)

  • Bile acids

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

Large Intestine

The large intestine lies like a frame around the loops of the small intestine. It is less flexible than the small intestine. The large intestine is also divided into different sections that have specific functions. The colon consists of the cecum and the vermiform appendix.

  • Large intestine (colon)

  • Appendix and vermiform appendix

  • and rectum (rectum with anal canal)

Behind the valve is a bulge in the lower right abdomen called the cecum. It forms the transition to the colon. A small, finger-like appendix (vermiform appendix) is attached to the cecum. This appendix can become inflamed and cause major problems, which is called, not quite correctly, "appendicitis".

The vermiform appendix is also called the "intestinal tonsil" because it has many defensive cells in its wall. If it is removed because of inflammation, there is no harm in doing so.

A shameful topic for many people, but an unavoidable, very natural process. A healthy gut flora and regular bowel movements have an impact on our health and well-being. On average, a healthy person passes about 100 to 200 grams of stool per day. Learn more about bowel movements here.

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Diseases like constipation, diarrhea, anal pain, and IBS

Irritable Bowel Syndrome

If the normal passage of food pellets is disrupted, problems can occur. When stool takes too long to reach the anus, more water is removed from the stool in the large intestine. This leads to very hard stools: constipation. In the worst case, this can lead to a bowel obstruction. Constipation can have many different causes and symptoms.

If the chyme is transported too quickly, it remains very liquid: Diarrhea occurs. It contains too much water and is harder to pass than normal stool. Our video explains what helps with diarrhea.

Anal pain

A common cause of pain when you have a bowel movement can be problems right at the anus or in the anal canal. The skin and mucous membranes in this area are very sensitive, so many people experience a lot of pain. It is also a very taboo subject, which is why many people do not seek medical help until it is too late.

Chronic inflammatory bowel disease

It is estimated that more than 400,000 people in Germany suffer from chronic inflammatory bowel disease. These include Crohn's disease and ulcerative colitis. They can occur at different stages of life and cause different, sometimes life-threatening symptoms. Both diseases have in common that parts of the intestine become severely inflamed. There are several treatment options. Click here for more information.

"Irritable bowel syndrome is the most common gastrointestinal disorder. It affects women twice as often as men. Symptoms range from nausea, abdominal pain, bloating, and a feeling of pressure or fullness to diarrhea or constipation.

A specific trigger for the digestive symptoms is not found in most cases.

However, it is not uncommon for people with IBS not to be systematically screened for other conditions and to be prematurely diagnosed with IBS and left alone, experts say.

In fact, many people with such symptoms would find a treatable cause, such as an allergy.

Causes of IBS

When IBS is present, it can severely limit quality of life. For some people, stress literally affects their stomach and intestines. The intestinal nerves go into a kind of permanent state of excitement, interfering with the regulation of bowel movements and telling the brain: "Pain!

A disturbed intestinal flora can be partly responsible: Antibiotics or severe gastrointestinal infections disrupt the natural mix of beneficial bacteria in the gut. After a Salmonella infection, for example, the risk of irritable bowel syndrome increases eightfold, but other intestinal bacteria such as Yersinia, Campylobacter or EHEC can also trigger the symptoms.

If the intestinal flora is damaged over a longer period of time (so-called dysbiosis), the intestinal mucosa can also change. It gets "holes" and becomes more permeable to toxins and pathogens. As a result, some people with IBS have more immune cells and their pro-inflammatory messengers in the gut, which in turn irritates the nerves in the gut.

Rule out other conditions with similar symptoms

There is often a long road to IBS diagnosis. First, other conditions with similar symptoms must be ruled out - for example, recurrent infections, food intolerances (such as fructose intolerance, other or multiple intolerances), food allergies, colonization of the bowel by bacteria, viruses or fungi, chronic inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, or even tumors in the bowel or ovaries.

Several tests should be done: Gastroscopy and colonoscopy, abdominal ultrasound, a blood test with CBC, liver enzymes, salts, thyroid and kidney values. A stool test can rule out parasite infestation. Breath tests can detect intolerance to certain types of sugar.

If all these examinations reveal no organic findings, and if intestinal disorders with the described symptoms occur for at least twelve weeks within a year, the diagnosis is irritable bowel syndrome.

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Are you tired of feeling bloated, gassy and uncomfortable after every meal? Do you suffer from cramps, diarrhea or constipation?

Then talk to one of our Experts and let them guide you.