False-colour x-ray of the abdomen showing the large intestine (colon). Contrast has been enhanced by a barium enema, whereby a suspension of barium sulphate (opaque to x-rays) is infused into the rectum. The colon begins at left (the small tail is the appendix) & consists of ascending, transverse, descending & sigmoid sections (the sigmoid colon is s-shaped & connects with the rectum). The colon is marked by haustra, compartments produced by infoldings of the mucular layer which supports the mucosal interior. The colon is responsible for water & electrolyte absorption; periodic muscular contractions move dehydrated contents towards the rectum.