How is water drawn out of the collecting duct?

Hypertonic conditions draws water out by osmosis in the collecting duct amount released to be retained is controlled by the ADH ADH is released by the posterior pituitary when the solute conc is high which is detected by the hypothalamus ADH increases permeability of collecting duct which upregulates the production of aquaporins (water channels) less water = concentrated urine WHen hydrates = less AH = less water is reabsorbed = dilute urine ADH = Are DeHydrated