The colon (also known as the large intestine) is part of the digestive system in eukaryotes. It is bigger in diameter than the small intestine, but smaller in length. One of its functions is to excrete and absorb substances that when dissolved become charged, in this way controlling the water content and subsequent osmolarity of the blood. In addition, it acts as a storage for faeces (product of undigested material, mucus and dead cells), before ejecting them to the outside of the body via the anus. As well as storing the undigested material, it also secretes a layer of mucus for smoother transport of the material through the rectum.