Caption

Large intestine. Coloured X-ray image of the human abdomen showing the large intestine (colon), after a barium enema. At centre are loops of the small intestine. These lead into the dilated colon, of which there are three regions. At left is the ascending region of the colon; at top, the transverse colon runs horizontally, leading to the descending colon (at right). At bottom centre is the rectum. The colon absorbs water and electro- lytes from digested food; periodic muscular contractions move the dehydrated contents (faeces) towards the rectum. A barium enema is a suspension of barium sulphate (which is opaque to X-rays) that is infused into the rectum.