Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The urinary system (also called excretory system or the genitourinary system) is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder, the urethra, and the penis in males. The analogous organ in invertebrates is the nephridium. The kidneys are bean-shaped organs, which lie in the abdomen, retroperitoneal to the organs of digestion, around or just below the ribcage and close to the lumbar spine. The organ is about the size of a human fist and is surrounded by what is called Peri-nephric fat, and situated on the superior pole of each kidney is an adrenal gland.