What is motility exactly?
In order for the body to be able to utilize the individual nutrients in the best possible way, it must break down the food into its smallest building blocks. Normally, the food stays in the stomach for about three hours before entering the small intestine and then into the colon. How fast the stomach is emptied depends also on the composition of the food.
In order to achieve the maximum effect, the digestive juices must already be well mixed with the food in the stomach. When the chyme reaches the intestines, it is further decomposed by the digestive enzymes from the pancreas. But that alone is not enough: In addition, it is essential that the decomposed food is transported in a controlled manner after each digestive step.
This is precisely why motility in the digestive tract plays such an important role: the stomach and intestine are able to move actively - in response to the position and amount of food to be digested.
The peristaltic contractions, wave-like muscle contractions, of the intestine assist in moving the chyme further along the gastrointestinal tract. This coordinated contraction and relaxation is reminiscent of the movement of an earthworm. How much the muscles move depends on the amount and position of the food. Segmental - limited to individual areas of the stomach or intestine - movements mix the food well. Gastric juice and digestive enzymes are distributed all over the chyme.
This motility is not coordinated directly by the brain, but rather by the enteric nervous system, that is the network of nerves in the digestive tract that comprises about as many nerve cells as the spinal cord. The enteric nervous system can act independently of the brain, but is - of course - connected to it and signals can be exchanged on both sides.