During digestion, our intestines use two different patterns of muscle contraction to move food through our bodies. Scientists have long wondered why we have this added complexity. Using numerical simulations of the fluid flow created by these contractions, researchers have uncovered the answer.
Our intestines use peristalsis, a forward-with-occasional-backward flow pattern, as the main driver. The strength of the muscle contractions determines how fast the average flow speed is. When the speed is slow, our bodies have more time to absorb nutrients, but that also allows more time for bacteria to flourish on those same nutrients. The other flow pattern, segmentation, creates a weaker flow overall but with much more mixing, which again enhances nutrient uptake.
Switching between the two patterns, the researchers found, gives the body the best of both. Segmentation can enhance mixing and provide good nutrient uptake, then peristalsis can move the contents along quickly enough that bacteria don’t have time to grow before getting flushed out. (Image credit: Kindel Media; research credit: A. Codutti et al.; via APS Physics)
