In this 100x view of the duodenum  the villi are clearly evident as is the simple columnar epithelial lining with the abundant goblet cells.   At the base between each villus lies an intestinal crypt which is the source of the mucosa cells. Because these villi extend in all directions, many of these crypts bend into the tissue beneath the epithelium and appear as seen here.  At the mucosa boundary lies the  muscularis mucosae.