Generating bowel movements that facilitate nutrient absorption

Abstract

When nutrients enter the intestine from the stomach, the movements of the intestine caused by contractions of the intestinal musculature (“intestinal motility”) have to fulfill the function of mixing the content with digestive enzymes and optimizing absorption by exposing all content to the lining of the gut. Intestinal motility is performed by smooth muscle cells and orchestrated by intestinal pacemaker cells and by a nervous system that is unique to the intestine. Movements to promote mixing are called “segmentation”, and movements that propel content along are called “peristalsis”. Peristalsis and segmentation in the human intestine are rhythmic and are governed by pacemaker cells called “interstitial cells of Cajal” or “ICC”. With peristalsis, a network of pace­maker cells generates a wave of electrical activity that propagates into the musculature and deter­mines the rhythm and propagation of contraction, similar to the pacemaker system of the heart. A recent discovery published in Nature Communications revealed that the segmentation motor pat­tern is initiated by certain nutrients that activate a second network of pacemaker cells. This second pacemaker activity is an electrical rhythmic signal that interacts with the first pacemaker activity, modifying it in such a way that the musculature responds with a completely different motility pat­tern; it changes the nature of the contractions from peristalsis to non-propulsive segmentation.