Peristalsis
From Freepedia
Peristalsis is the process of involuntary wave-like successive muscular contractions by which food is moved through the digestive tract.
The large, hollow organs of the digestive system contain muscle that enables their walls to move. The movement of organ walls can propel food and liquid and also can mix the contents within each organ. Typical movement of the Oesophagus, stomach, and intestine is called peristalsis. The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.
The process of peristalsis is used by peristaltic pumps.
Peristalsis is also used at oviducts, ureters and other tube-like organs.
In the digestive tract, the muscularis externa (which consists of circular and longitudinal muscle) propels the material along the alimentary canal. During a peristaltic movement, the circular muscles contract behind the digested material; then a contraction of the longitudinal muscle follows which pushes the digested food further along the oesophagus. (These peristaltic movements also occur in the large and small intestines.)
