The bowel is part of our digestive system. It is divided into two parts, the small bowel and the large bowel. The large bowel is made up of the colon and rectum.

Once food has been swallowed, it passes down the gullet (oesophagus) to the stomach, where digestion begins. It then passes through the small bowel, where essential nutrients are taken into the body. The digested food then moves into the large bowel, and water is absorbed by the colon. The colon starts at the bottom, right-hand side of the abdomen. The first part goes up and is known as the ascending colon. It then goes across to the left side of the abdomen. This part is called the transverse colon. It then goes down to the bottom of the abdomen: this part is called the descending colon, and ends in the sigmoid colon, rectum and anus.

The remaining waste matter, known as stools or faeces, is held in the rectum (back passage) until it is ready to be passed from the body through the anus as a bowel motion (stool). Close to the bowel are lymph nodes, also known as lymph glands, which are about the size of a baked bean. The lymph nodes are part of the lymphatic system.

Nearly all bowel cancers develop in the large bowel – two-thirds of these are in the colon and one-third in the rectum.

You can find information about cancer of the small bowel later in this section.