Female urinary system revealing posterior views of the kidneys, ureters, bladder and urethra. The urinary system is responsible for fluid balance and waste excretion. Blood enters the kidneys where waste products are excreted to form a fluid called filtrate. Filtrate continues to collect additional waste products and minerals as it travels through the winding tubules of the kidney. Eventually, the filtrate becomes urine as it is channeled out of the kidney, into the ureters, down to the bladder and eventually out through the urethra to the external body.