part of collecting duct medullary collecting duct 2010-02-16T10:27:23Z BTO:0004536 BrendaTissueOBO Medullary collecting ducts are divided into outer and inner segments, the latter reaching more deeply into the medulla. The variable reabsorption of water and, depending on fluid balances and hormonal influences, the reabsorption or secretion of sodium, potassium, hydrogen and bicarbonate ion continues here. mgr