colon

Segment that makes up most of the large intestine. Though the two terms are often used interchangeably, the colon technically excludes the cecum (a pouch at the beginning of the large intestine), rectum, and anal canal. It runs up the right side of the abdomen (ascending colon), across it (transverse colon), and down the left side (descending colon); its last section (sigmoid colon) joins the rectum. It has no digestive function but lubricates waste products, absorbs remaining fluids and salts, and stores waste products until excretion. Problems involving the colon include ulcerative colitis, constipation and diarrhea, gas discomfort, megacolon (enlarged colon), and cancer.