[1] Polychaetes typically release their gametes into the water column using nephridiopores.
[2] Nephridia are homologous to nephrons or uriniferous tubules found in the kidney of humans.
Body fluids are filtered in through the nephrostome and passed through the convoluted tubule system.
[3] Essential substances are reabsorbed through active mechanisms and waste products are secreted back into the lumen of the tube.
[4] The resulting excretory fluid or urine is passed out through the nephridiopore.