Function and tasks
In the large intestine, the intestinal contents are primarily thickened and mixed. In addition, the large intestine is responsible for the urge to defecate and the evacuation of stool. 1. motility By motility the physician understands the entirety of the movements of the large intestine.
They serve to thoroughly mix the food, but also to transport the contents of the bowel towards the rectum: a)Mixing movementsThey take up the main part of the movements in the colon and are rather slow with a maximum frequency of 15 movements/minute. In a normal and healthy adult, the food pulp remains in the colon for between 20 and 35 hours. However, this time varies considerably, so that depending on the food components and mental condition, the length of stay can increase to up to 70 hours!
The strong mixing of the intestinal contents ensures a sufficient reabsorption of important nutrients and water. b) Transport movementsTransport movements are rather rare in the large intestine. But they occur especially after meals as so-called “mass movements”.
They transport the intestinal contents into the rectum and are associated with the urge to defecate when the intestine is sufficiently filled. This is often followed by defecation with a total daily stool quantity of about 100-150g per day. 2. resumptionIn principle, the colon plays a rather subordinate role in the resumption of nutrients and water.
A large part of this happens already in the small intestine, so that the faeces are only finally thickened and covered with a slippery layer of mucus. 3. intestinal floraOur large intestine is naturally home to a large number of bacteria that perform indispensable functions in digestion. It is estimated that there are approximately 1011-1012 bacteria per milliliter of intestinal content! They break down undigested plant fibers (e.g. cellulose) and produce important nutrients such as biotin (vitamin B7) or vitamin K.
Stool reflex (defecation reflex)
When the rectal ampoule fills with feces, the intestinal wall is stretched at this point and the filling status is measured by receptors (feelers). The stretch receptors send signals via nerves to the circuit systems in the spinal cord and brain. If the defecation is “allowed” by the brain, a signal is sent to relax the outer anal sphincter muscle, thus initiating the defecation.
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