This post contains many high yield images that help to identify some of the identifying features of the duodenum. If you haven't already, be sure to read A Histology Tour of the GI Tract- Small Intestines Overview before continuing...
After food has traveled through and been partially digested in the stomach, the next stop is the duodenum. The duodenum is the first (and shortest) segment of small intestine, about 25 cm long.
Functions of the Duodenum
Villi have absorptive function