In the presence of vasopressin, which pa of the nephron reabsorbs greatest fraction of filtered water?
Proximal tubule is highly water permeable. Here, 65% of the filtrate is reabsorbed, driven by active transpo. As ions are reabsorbed water follows by osmosis. Vasopressin influences water permeability only in the distal and collecting tubules. It has no influence over the 80% of the filtered water that is reabsorbed without control in the proximal tubule and loop of henle. Ref: Fundamentals of Human Physiology By Lauralee Sherwood , Page 408; The Renal System at a Glance By Chris O'Callaghan, 3rd Edition, Page 33.
Proximal tubule
Distal tubule
Loop of Henle
Collecting duct