The digestive system is made up of the esophagus (food pipe), stomach, and the small and large intestines. The upper 5 - 6 ft (1.5-1.8 m) of the large intestine is called the colon, and the last 6 - 8 in (15-20 cm) of the colon is the rectum. Colorectal cancer is a disease in which the cells of the tissues lining the colon and the rectum start to grow uncontrollably and form tumors.

The main function of the colon is to absorb water and the nutrients from the food already digested by the stomach and the small intestine. The waste material left behind goes into the rectum. From here, it is excreted out of the body through the anus. The colon has four sections: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon which extends to the rectum. Cancer can develop in any of the...