The intestine as a fluid propelling system

The ability of intestinal segments to propel fluid from their lumens can be characterized in dynamic terms by measuring the movement of luminal fluid ejected into attached systems that predispose the amount of work the segment must do to affect fluid transfer. Studies employing this approach have demonstrated that the propulsive capability intrinsic to intestinal and colonic segments is not uniform along the bowel. Differences in propulsive behavior observed to occur solely as the result of the operation of subsystems intrinsic to particular intestinal regions suggest (a) that external control inputs can alter the propulsive state of a region, and (b) that this altered state may exist for hours after the external input to the system is terminated. Consideration of the propulsive performance of segments as an emergent property of interactions among intrinsic subsystems has contributed to the formalization of precise questions heretofore not asked about the organization and function of intestinal subsystems and their associated interactions. Knowledge of propulsive behavior and its control is still in its infancy. Further studies employing basic concepts and procedures similar to those reviewed above will advance our understanding of intestinal propulsion and of the intestine as a complex system.