AbstractMucosal reduplications of the ampullary mucosa in the major duodenal papilla have been found to be of two types: (1) columnar‐shaped projections apparently related to the wall of the terminal bile duct in adults only, are structures acquired postnatally; (2) leaf‐like flaps that are generally transversely oriented along the caudal wall of the ampullary space both in adults and in fetuses are congenital structures concerned in guarding the orifice of the main pancreatic duct against the incursion of back‐flowing fluids.