Peristaltic Motion in Digestion
Peristaltic motion is a kind of wave motion that occurs within tubular structures that force the movement of an object or medium. An excellent example of this occurs in the digestive tract where food is forced through the system by the contraction of successive muscles. Earthworms use this same process for locomotion.
Within the esophagus, peristaltic motion is used to force food into the stomach. It should be noted that in vomiting peristaltic motion does not go into reverse. Vomiting is caused by contractions of muscles in the abdomen. A primary peristaltic wave occurs when a bolus of food is initially swallowed. The straight wave lasts seven to ten seconds. The wave continues at the same rate whether or not the bolus actually moves with it. So it may happen that the bolus does not get to the stomach via the primary wave. Should this occur, the bolus will stimulate secondary peristaltic waves, which will continue until the bolus reaches its destination.
After processing in the stomach, food is let into the small intestines, where very small parastaltic motions occur. This helps to churn the content as well as slowly move it along. Much greater perastaltic motion occurs in the large intestines on a periodic basis, usually one to a few times per day. Which will finally cause the now processed food to be expelled from the digestive system.
Abnormal parastaltic movement can be a factor in irritable bowl syndrome, diarrhea, constipation, and other intestinal problems. It is thought that normal parastaltic movement may be aided by the consumption of green leafy vegetables, including lettuce. Some sources report that this may also be one of the health benefits of cilantro.