Duct of Bellini is one of the main urinary ducts of the mammalian kidney acting as a common collecting duct receiving branches from a number of Malpighian bodies. All duct of Bellini then, open at the tip of the papilla or papillae into the pelvis. Ureters are narrow tubes with a thick muscular wall having an outer fibrous coat, a middle muscular coat and an inner mucous membrane.