ABSTRACT
Physiology of Normal Motility Motility of the gastrointestinal tract has two major effects. One is to facilitate the absorption of nutrients. Both retrograde and normograde flow are required to optimize the absorption of nutrients. Retrograde flow most likely occurs intermittently over short distances to aid in mixing of ingesta and exposing nutrients to the mucosa for absorption. Although little work has been done in the horse to investigate the control of these mixing patterns, most likely feedback occurs from both absorption of nutrients and afferent input by mucosal sensory receptors that control these mixing motor patterns in a similar fashion to other species. The second major effect of motility is to maintain the aboral propagation of chyme and indigestible material. Because alteration of the normal aboral movement of ingesta causes immediate clinical consequences, the majority of motility investigation in the horse has centered around the control of aboral propagation of ingesta throughout the gastrointestinal tract and the pathophysiology associated with delayed aboral propagation. This chapter will review the basic mechanisms controlling normal motility patterns, review current thoughts as to the mechanisms underlying the pathophysiology of motility disturbances, in particular postoperative ileus, and finally, review prokinetics that are available to the equine practitioner.
