Rectum:The final section of the large intestine, terminating at the anus, where waste material is stored before it is expelled from the body.
Sphincter Muscles: Circular muscles that constrict or dilate to regulate the passage of substances through an opening; in this context, controlling the release of feces and gas from the anus.
Feces: Waste matter discharged from the bowels after food has been digested; essentially, solid bodily waste expelled through the rectum