collecting tubule [L, colligere, to gather, tubulus, small tube] , any one of the many relatively straight tubules of the kidney that funnel urine into papillary ducts in the renal pelvis. The small collecting tubules play an important role in maintaining the fluid balance of the body by allowing water to osmose through their membranes into the interstitial fluid in the renal medulla. Antidiuretic hormone in the blood makes the collecting tubules permeable to water. If no antidiuretic hormone is present in the blood, membranes of the collecting tubules are practically impermeable to water. See also Bowman’s capsule, kidney.
