Peristalsis

Peristalsis (/ˌpɛrɪˈstælsɪs/ PERR-ih-STAL-siss, US also /-ˈstɔːl-/ -⁠STAWL-)[1] is a type of intestinal motility, characterized by radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction.

[4] The word comes from Neo-Latin and is derived from the Greek peristellein, "to wrap around," from peri-, "around" + stellein, "draw in, bring together; set in order".

[6] The food bolus causes a stretch of the gut smooth muscle that causes serotonin to be secreted to sensory neurons, which then get activated.

Activated neurons of the retrograde pathway release substance molecules alsoP and acetylcholine to contract the smooth muscle behind the bolus.

The activated neurons of the anterograde pathway instead release nitric oxide and vasoactive intestinal polypeptide to relax the smooth muscle caudal to the bolus.

The churning movements of the stomach's thick muscular wall blend the food thoroughly with the acidic gastric juice, producing a mixture called the chyme.

Mass movements often tend to be triggered by meals, as the presence of chyme in the stomach and duodenum prompts them (gastrocolic reflex).

During ejaculation, the smooth muscle in the walls of the vasa deferentia contract reflexively in peristalsis, propelling sperm from the testicles to the urethra.

As a result, each segment is extended forward, then relaxes and re-contacts the substrate, with hair-like setae preventing backward slipping.