Functions of the Colon

Synonyms in a broader sense

Colon, interstitium grassum, rectum, rectum

English: colon


The main task of the large intestine is to absorb water from the stool and transport it to the anus.
At the same time, minerals are removed from the food residues and the stool is thickened.
The nutrients from food have already been absorbed in the small intestine, which lies in front of the large intestine.

The large intestine is also home to a large number of bacteria that digest food components that are indigestible for us. But the large intestine is not only important for digestion, it also plays a role in the immune system.

Functions of the Colon

The task / main task of the large intestine is to remove water from the intestinal contents (Absorption) so that the body does not lose large amounts of fluids. By giving up withdrawal from water and Minerals (Electrolytes) the chair becomes thicker and firmer as it passes. In order for the chair to move forward despite its increasing strength, the ability to slide must be guaranteed. For this purpose, the Goblet cells incessantly mucus produced. The absorption of fluid reduces the volume of the stool to 150-200 ml per day.

The rectum (rectum) then takes on the task as reservoir (Rectal ampoule), where the stool is temporarily stored. When a certain storage volume is reached, the Evacuation reflex (Defecation reflex) triggered and the stool emptied in a controlled manner. Of the Large intestine is also with bacteria (Microflora) that perform various tasks. These bacteria do one Barrier functionbecause they are partly the undesirable Penetration of foreign substances (allergens) in the intestinal wall prevent them from stimulating the Colon movement (Motility/peristalsis) on and stimulate that immune system. In addition, bacteria can themselves Make vitaminswhich the intestine can then absorb. Certain drugs (e.g .: Antibiotics), radioactive rays and malnutrition (e.g. too much sugar) can lead to disturbances of the microflora and complaints such as Flatulence, Metabolism, and immune defense problems arise.

Illustration of the large intestine

Figure large intestine: location of the digestive organs in the body cavity (large intestine-red)
  1. Colon, ascending part -
    Ascending colon
  2. Appendix - Caecum
  3. Appendix -
    Appendix vermiformis
  4. Right colon bend -
    Flexura coli dextra
  5. Large intestine, transverse part -
    Transverse colon
  6. Left colon bend -
    Flexura coli sinistra
  7. Large intestine, descending part -
    Descending colon
  8. Large intestine, s-shaped part -
    Sigmoid colon
  9. Rectum - Rectum
  10. Bulges of the
    Colon Wall -
    Haustra coli
  11. Liver - Hepar
  12. Stomach - Guest
  13. Spleen - Sink
  14. Gallbladder -
    Vesica biliaris
  15. Small intestine -
    Intestine tenue
  16. Esophagus -

You can find an overview of all Dr-Gumpert images at: medical illustrations

Role of the large intestine in digestion

True, be in the colon hardly any nutrients absorbed, with the exception of short-chain fatty acids, which are already absorbed in the small intestine, but nevertheless, the colon is important.

First and foremost, it is crucial to the Maintaining our water balance involved.
The colon takes up about 80-90% of the water in the stool. This prevents the body from losing too much fluid. There is only about 0.1 liter of water in the excreted stool.
If this function of the colon is disturbed, e.g. Due to bacterial toxins, the loss of water can lead to life-threatening diarrhea.

With the water the large intestine also removes salts from the stool, primarily NaCl. Sodium and chloride are necessary for numerous processes in the body and for maintaining the osmotic environment in the cells. That is why it is important to ensure adequate fluid and electrolyte intake when having diarrhea. A large amount of water and electrolytes are already absorbed in the small intestine.

It is even possible to live without a colon, however, more attention must then be paid to diet and fluid intake.
The last portion of the colon that Rectum, also has a Reservoir function for the bowel movement. Because of this and the thickened stool, people have an average of once a day bowel movements.

In contrast to the small intestine, the large intestine houses Lots of bacteria. The large intestine has the greatest density of these small creatures in the entire body.
Here you digest food components that our body cannot digest itself. Mostly this is fiber-rich food.
The bacteria release nutrients from these otherwise indigestible foods, which on the one hand feed the bacteria themselves and on the other hand can be absorbed by humans. Thereby the bacteria optimize our food intake. Dead bacteria are simply excreted and make up most of our stool.

Interestingly, today we assume ours Intestinal flora have an impact on our weight depending on which strains of bacteria we harbor in our large intestine. The intestinal flora can change in the course of our lives and probably also has an impact on our health.


Of the anus Occlusion prevents stool or gases from accidentally escaping from the bowel. Various mechanisms are required for this:

  1. Tasks of the internal anal sphincter (Sphincter ani internus): This sphincter is made up of smooth muscles and therefore cannot be controlled willingly,
  2. Tasks of the external anal sphincter (External ani sphincter): With this sphincter, which consists of transversely striped muscles, one can hold the chair and thus actively regulate the time of the bowel movement.
  3. Tasks erectile tissue (Corpus cavernosum recti): If the rectal ampoule is filled accordingly, this erectile tissue can fill up particularly heavily with blood and thus support the sphincter through increased sealing.