Intestinal structure
Life is not possible without intestines. It controls and ensures the vital digestion. Via the intestine, food and liquids enter the human body, and here the splitting into usable and non-usable ingredients of food takes place.
The human intestine is divided into numerous sections, which have correspondingly different tasks and proportions in the digestive process. The main division is the distinction between the small intestine and the large intestine. The small intestine with all its sections is connected to the stomach.
A distinction is made between the duodenum, which is directly connected to the stomach outlet. In it, the bile acids are transported from the gall bladder, where they are stored, to the food, which is already sufficiently reduced in size and mixed with liquid in the duodenum. It is now more like a chyme that forces its way through the narrow intestinal plexus by rhythmic muscle movements.
The chemical digestion of the chyme begins with the mixing of bile acids. Produced by the pancreas, enzymes enter the small intestine, which break down the various fats. The most important enzymes are lipase and amylase.
The duodenum is followed by the jejunum. It makes up about 40% of the small intestine. The remaining 60% are formed by the so-called ileum.
The main function of these sections of the small intestine is to knead the food and absorb nutrients. Thus, in addition to the required nutrients, folic acid, vitamin C and calcium are also removed from the chyme in the small intestine. Since food is also contaminated with bacteria to a not inconsiderable extent, a large part of the human immune and defence system is located in the intestine to quickly render corresponding pathogens and intruders harmless.
The defence system is in the form of lymphatic structures. The optimal resorption of nutrients is achieved by a mucosa that spreads in waves and slides out the entire inner wall of the small intestine. The villi protrude into the intestinal lumen and thus come into contact with the chyme which is pushed through the intestine.
Shortly after the duodenum, the villi are at their largest, the further down the intestine the flatter they become. Up to the large intestine they are almost invisible. The small intestine takes up a large area, which is also increased by the refined folding.
It also offers a large surface area for diseases. Common intestinal diseases can be autoimmune and are called ulcerative colitis or Crohn’s disease. Symptoms are severe diarrhoea, sometimes associated with blood and cramps.
The small intestine is followed by the large intestine, which is also known as the colon. Here there is no longer the anatomical elevation of the mucous membrane that protrudes into the chyme. The walls are flatter and smoother, and much of the nutrient utilization is already completed in this section of the digestive tract.
The colon begins at an anatomical structure that strictly separates the small intestine from the large intestine. This structure is also called Bauhin’s valve. It is followed by the appendix, which in most people is located in the lower right abdominal section.
While it was previously believed that this section of the intestine has no essential functions, it is now known that a large part of the immune response is generated in the appendix. Most people are familiar with this part of the intestine, possibly from their own experience, because the spinous process of the appendix can become inflamed and in most cases must then be surgically removed. By definition, the actual large intestine (colon) begins directly behind the appendix.
The colon is divided into an ascending part (pars ascendens), a transverse part (pars transversum) and a descending part (pars descendens). Seen from the front, the colon forms a kind of frame in the middle of which the small intestine is embedded. Seen from the outside, the large intestine is characterized by constrictions, also known as housetrenches.
Its main function is to absorb minerals and extract water from the chyme. In total, the large intestine can process 300 ml of chyme into 150 g of bowel movement. In addition to the absorption of important minerals, substances are also released into the intestine and thus excreted.
The most important of these are potassium and bicarbonate, which have important buffering functions and are excreted via the intestine in the event of increasing alkalisation of the body. In addition, many toxins are ultimately excreted through the large intestine and thus leave the body unnoticed. The intestine is by no means sterile and is flooded with numerous bacteria that belong to the intestinal flora.
The task of the numerous bacteria is to defend against pathogens through a natural barrier function, support the metabolism at the colon mucosa and accelerate exchange processes (exchange of nutrients etc. at the intestinal wall). They also stimulate intestinal activity and the mechanical movement of the intestine.
In addition, the stimulation of the immune system is also counted among the tasks of the bacteria. The intestinal flora maintains an optimal environment in the intestine, which maintains the exchange processes of nutrients and harmful substances. An imbalance of the intestinal flora leads to the upsetting of the balance and ultimately to diarrhoea. This is often observed after prolonged antibiotic use.