How the Digestive System Works

The digestive system begins at the mouth and ends at the rectum and anus, where solid waste is expelled from the body after water and nutrients have been absorbed.

The inside of the anus is lined with glands and four to six crypts, or pockets. Several muscles ring the anal canal and work together to control bowel movements. The inner muscle, just beneath the lining of the anal canal is called the internal involuntary anal sphincter. This muscle is usually contracted to close the anal canal. When a bowel movement occurs, the muscle relaxes to allow the stool to pass.

Anorectal Disorders

Anorectal disorders can be caused by body structure, diet, lifestyle and bacteria present in the waste produced by the body. The most common of these are:


Although many people are reluctant or embarrassed to see their doctors about anorectal disorders, doing so is a critical step to maintaining good health. Diseases, such as colon or anal cancer, have symptoms that can be mistaken for those of less serious anorectal disorders, such as hemorrhoids or fissures. Only a physician can make an accurate diagnosis of what is causing the symptoms. Some anorectal disorders, such as abscesses, can be lead to cancer of the colon, anus or rectum.