Nephridiopore

[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.