Similar to the rest of the GI tract, the large intestine has a mucosa, submucosa, muscularis externa and serosa. The luminal surface of the mucosa appears relatively smooth because there are no villi in the large intestine.  There are, however, numerous crypts of Lieberkühn that extend all the way to the muscularis mucosae. The epithelium of the mucosa consists of simple columnar epithelium and some mucus-secreting goblet cells.  Note that the number of goblet cells increases in the crypts.