Medulla: Papillary ducts

The papillary ducts of Bellini, the distal-most portions of medullary collecting ducts, are located in the deepest portion of the medulla. Papillary ducts have the tallest epithelium of the collecting ducts, consisting of pale staining principle cells and the less numerous, darker-staining, intercalated cells. Intercalated cells often bulge into the lumen of the tubule. Papillary ducts terminate at the area cribosa of the papilla, passing urine into the minor calyx. 10x, 400x

Principle cells are the major target for the hormone aldosterone, which regulates the tonicity of urine. These pale-staining principle cells also line connecting ducts and other portions of collecting ducts. Intercalated cells play an important role in acid-balance balance.

Principle cells are the major target for the hormone aldosterone, which regulates the tonicity of urine. These pale-staining principle cells also line connecting ducts and other portions of collecting ducts. Intercalated cells play an important role in acid-balance balance.