Introduction to Gut Motility and Sensitivity

Abstract

Whether or not one believes in the theory of evolution, it is apparent that some of the first multicellular organisms to have inhabited the earth, including the presumptive earliest ancestors of humans, were elongated structures with a core gut tube (The quest for food: a natural history of eating, New York, 2007; Genesis 46:605–13, 2008). In the absence of an obvious heart, brain, or liver, this core system helped sustain life by performing fundamental processes including respiration, the assimilation of nutrition, and metabolism. On this basis it is perhaps not surprising that the gastrointestinal (GI) tract has evolved to become one of the most complex and diverse organs of the human body, with an incredible repertoire of activities from digestion, absorption, and excretion to homeostatic, endocrine, and immune functions. Many of these processes are dependent on highly coordinated sensory and effector mechanisms, which monitor the GI lumen and wall and respond to specific cues. In conjunction with a drive to maintain homeostasis within the body, the effector mechanisms regulate blood flow, adjust the balance between absorption and secretion, and coordinate mixing and propulsion of luminal contents along the length of the bowel. This latter “motility” activity is executed by region-specific peristaltic contractions and emptying mechanisms, which are dependent on highly coordinated interactions among the components of the gut neuromusculature.