Nephron is the structural and functional part of the kidney. It consists of the renal corpuscle, and renal tubule. PCT is the main site of absorption as all essential nutrients and 70-80% of electrolytes and water are reabsorbed here. thus the filtrate remains isotonic here. The ascending limb of Henle's loop is impermeable to water and permeable to electrolytes.The filtrate from here passes into the DCT hence it is hypotonic to it.ADH hormone absorbs water from DCT and thus filtrate becomes hypertonic.