The epithelia of the villi extend down into the lamina propria where they form crypts. Many important cells reside in the crypts, including those involved in host defense and signaling. An intestinal gland (also crypt of Lieberkühn and intestinal crypt) is a gland found in the epithelial lining of the small intestine and colon. Intestinal crypts are found in the epithelia of the small intestine, namely the duodenum, jejunum and ileum. Intestinal crypts contain a base of replicating stem cells, Paneth cells of the innate immune system and goblet cells, which produce mucous. In the colon, crypts do not have Paneth cells.