About 10 hours after you have eaten, the undigested food reaches the large intestine. It may take another 20 hours to pass completely through the body. The large intestine is divided into three parts-the ascending colon, transverse colon and descending colon. They are called so because that they lead up, across and down. The waste material that gathers in the large intestine is called faeces. It consists mostly of dead cells from the gut wall, the remains of digestive juices, bacteria and some water, as well as hard indigestible bits of food, mainly the fibres from fruit, vegetables and grain. Bacteria in the large intestine produce certain vitamins that are absorbed into the blood. They also produce foul-smelling gases. The faeces are excreted around twenty-four hours after first being swallowed.