A bowel movement is the process by which the body expels stool (also called feces) through the rectum and anus. It is the final step in the digestive process, where the indigestible parts of food, along with bacteria, mucus, and cells from the intestines, are eliminated from the body
. Stool is composed mostly of water (about three-fourths), with the remainder including bacteria, fats, fiber (undigested food), food wastes, mucus, salts, and bilirubin, which gives stool its brown color
. The digestive system absorbs nutrients and fluids from food, and the leftover waste forms the stool that is eventually passed during a bowel movement
. The movement of stool through the intestines is facilitated by muscular contractions called peristalsis, which push the waste through the colon to the rectum, where it is stored until elimination
. The process of defecation involves both involuntary and voluntary muscle control: the internal anal sphincter is involuntary, while the external anal sphincter is under voluntary control, allowing a person to control when to have a bowel movement
. Normal bowel movements vary in frequency from several times a day to a few times a week, and the stool should be firm, moist, and easy to pass
. Abnormalities such as diarrhea occur when stool passes too quickly through the large intestine, and constipation occurs when it moves too slowly
. In summary, a bowel movement is the body's natural way of eliminating waste products from digestion, essential for maintaining health by preventing the buildup of waste in the colon
