(June 2011). The nephron (from Greek νεφρός - nephros, meaning kidney) is the basic structural and functional unit of the kidney. Its chief function is to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine.June 2011). The nephron (from Greek νεφρός - nephros, meaning kidney) is the basic structural and functional unit of the kidney. Its chief function is to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine.