Basis for understanding resorption — histological structure of the gastrointestinal tract
In terms of developmental history, our digestive system is the oldest organ system in the body. The main role in digestion is played by the small intestine: it is here that — after the digestive enzymes have done the necessary preliminary work — the micro- and macronutrients that are so important for us are transported from the food into the body. To achieve the best possible absorption surface, nature has enlarged the inside of the small intestine many times over. Its mucosa lies in millions of folds that are about one millimeter in size (intestinal villi). As a result of this “folding” technique, the small intestine, which is about 4–6 meters long, has a total surface area of almost a tennis court (about 250 m2) — enough space to absorb vital nutrients and deliver them to the blood and lymphatic systems.
How is the intestine structured?
The intestine is roughly divided into the small intestine, large intestine and rectum. The long, multiply coiled small intestine begins directly behind the stomach and consists of the short duodenum, the jejunum and the ileum. The average length of the small intestine in an adult male is 6.9 m, and 7.1 m in an adult female. It can vary greatly, from 4.6 m to 9.8 m in length. The duodenum is where most of the chemical digestion takes place, as the bile and pancreatic fluids flow directly into it. The jejunum is where most of the carbohydrates and proteins are absorbed, and the ileum is where vitamin B12, bile salts and all other digestive products are absorbed.
At the end of the ileum in the right lower abdomen, the small intestine opens into the large intestine, which is about 1.5 meters long and surrounds the small intestine in the form of an inverted “U”. Above this opening, at the caecum and appendix, the colon begins to ascend (colon ascendens) to the right upper abdomen below the liver, it then runs horizontally (colon transversum) through the upper abdomen to below the spleen, and on the left abdomen it descends again (colon descendens) to the left lower abdomen. With an S-shaped curve, the sigmoid colon (colon sigmoideum), the large intestine finally passes into the rectum, which is closed by the anal sphincter.
Is the intestine smarter than our brain?
Before nature decided to form a brain as a control center for more complex organisms, the first nerve cell structures were already present in the digestive system. Today, the “abdominal brain” consists of about 100 to 200 million nerve cells that run in the muscle layers of the intestinal wall. In comparison, a dog — being a very intelligent animal — has only about 160 million nerve cells in its cerebral cortex.
The microscopic inhabitants that feel so at home in the intestinal mucosa have various tasks: They digest indigestible food components (dietary fiber) and produce substances that supply the top layer of the intestinal mucosa with energy. They form a protective shield against pathogenic germs and prevent them from entering the body.
The intestinal flora also interacts with the intestinal immune system. It trains the immune cells and stimulates the formation of defense substances, which benefit not only the intestine but also other areas such as the nasal mucous membranes. All this makes the intestine an important part of the immunological network. This is also reflected in figures: the small and large intestine contains 70% of all immune cells and is involved in almost 80% of all defense reactions. While primitive peoples, such as in the Amazon, have many different intestinal bacteria, people in more developed countries have already lost 40% of the species in their intestinal flora due to lifestyle and diet. This makes it all the more important to keep the intestine and its inhabitants as healthy as possible.
Gut good, everything good!
In the beginning, there is the intestine — not only developmentally, but also when it comes to our well-being and health. A gut-friendly diet is varied, unprocessed, organic, regional and plant-based. But what else can we actually do to make the gut and its housemates feel good?
What can we do to make our intestines and their inhabitants feel good?
- Intestinal bacteria love dietary fiber: Soluble dietary fiber, which is found primarily in plant foods, is broken down by bacteria in the colon. The dietary fiber serves as food for the good bacteria
- Prefer bitter: Certain plants that are rich in bitter substances, such as milk thistle or artichoke, can stimulate the liver and gall bladder and thus support the digestive function of the intestine
- A good supply of vitamins A, B2, B3 and biotin helps maintain normal mucous membranes
- Convenience products? No thanks! Ready-made products often contain a number of additives that can negatively affect the composition of the intestinal flora
- Less sugar: Sugar favors the less optimal types of bacteria and fungi in our intestines
- Regular exercise: If you do endurance sports (e.g. jogging or cycling) three times a week, you help to keep your circulation and intestines healthy. Improved blood circulation benefits digestion
- Caution: Germ-free! Cleanliness is important. No question about it. However, excessive hygiene can be detrimental to our microbiome. There is a reason children are allowed to play in the dirt as a precautionary measure
Text Sources:
(1) Franz, M., Gruber, K. 2007. Wunderwelt: Eine Geschichte des menschlichen Körpers. Verlagshaus der Ärzte, 1. Auflage.
(2) Grillpazer, M. 2006. KörperWissen: Entdecken Sie Ihre innere Welt. Gräfe und Unzer Verlag GmbH.
(3) https://www.medizinpopulaer.at/archiv/medizin-vorsorge/details/article/was-dem-darm-gut-tut.html
(4) https://www.mdr.de/wissen/darmhirn-100.html
(5) https://www1.wdr.de/wissen/mensch/bauch-zweites-gehirn-100.html
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