In the presence of ADH, greatest fraction of the filtered water is reabsorbed from:
65%-70% of the filtered water is reabsorbed from the PCT. This is called obligatory water reabsorption and occurs irrespective of the osmolarity of ECF. In the complete absence of ADH action, 88% of the filtered water is reabsorbed from various segments of nephron. 10%-12% water is reabsorbed from collecting duct under the maximum action of ADH. This is called facultative water reabsorption. Water reabsorption from the collecting duct is determined by osmolarity of ECF.
PCT
Loop of Henle
DCT
Collecting duct
Excretory System (Kidney, Bladder) Acid-Base Balance