Peristalsis is synchronized or coordinated contraction of the muscles that
surround tubular organs. Waves of peristalsis, for example, propel food
content through the gastrointestinal
tract (GI tract) to facilitate normal digestion and the absorption of nutrients. Peristalsis is dependent upon the coordination
between the muscles, nerves, and hormones in the GI tract. It is effected
by the autonomic nervous system plexuses acting on visceral muscle layers. The reverse process, antiperistalsis,
|The walls of the GI tract have an inner, circular
muscle fibre coat and an outer, longitudinal muscle fibre coat. As
the ball of food (bolus) formed in the mouth enters the pharynx, a
reflex action is initiated. This produces slow, wave-like contractions
in the walls of the esophagus and later along the whole length of
the tract. These peristaltic waves involve the contraction of the circular
muscle fibres behind the bolus (A) and their relaxation in front of
the bolus. Longitudinal muscles provide the wave-like action. The
two functions together push the ball down the tract (B).
Peristalsis also occurs in the ureter.