Large intestine. Coloured X-ray of the large intestine (colon) and rectum, the final parts of the digestive system. This view is from the front. The ascending colon (left), transverse colon (top), and descending colon (right) lead to the rectum (bottom centre). Digested food passes from the small intestine to the large intestine. The main function of the large intestine is to absorb water and minerals, as well as reabsorbing water used to digest the food. The compacted faeces are then passed to the rectum to be expelled from the body. This X-ray is a double contrast X-ray, a technique that highlights the soft tissues, air spaces, and digested food of the intestines. The X-ray also shows the bones of the lumbar spine and the pelvis.