The contraction and relaxation of smooth muscles of GI tract,
especially in esophagus that creates a wave to push the food
contents in forward direction is called peristalsis.
Circular smooth muscles are involved in peristalsis.
Peristalsis generates a one way directional wave.
The speech of food content propagation increases with
peristalsis.
Segmentation
The contractions of smooth muscles of GI tract, especially in
small intestine in order to mix the chyme with intestinal juices is
called segmentation.
Longitudinal smooth muscles are involved in segmentation.
The movement of food content occurs in both forward and
backward directions.
This process slows down the process of food content propagation
to allow digestion and absorption of nutrients.