part_of part of part of has_part has part has part collecting duct of renal tubule nephron kidney epithelial tube kidney epithelium excretory tube uriniferous tubule Functional unit of the kidney that forms urine, consisting of two parts, the nephron and the collecting tubule. uberon FMA:17691 UBERON:0007684 functional unit of the kidney that forms urine, consisting of two parts, the nephron and the collecting tubule.