In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammals. It is the organ that collects urine excreted by the kidneys prior to disposal by urination. Urine enters the bladder via the ureters and exits via the urethra.In males, the bladder is superior to the prostate, and separated from the rectum by the rectovesical excavation.In females, the bladder is separated from the rectum by the rectouterine excavation, and it is separated from the uterus by the vesicouterine excavation.