<P> For the urine to exit the bladder, both the autonomically controlled internal sphincter (in the male) and the voluntarily controlled external sphincter must be opened . Problems with these muscles can lead to incontinence . </P> <P> The human urinary bladder derives from the urogenital sinus, and it is initially continuous with the allantois . The upper and lower parts of the bladder develop separately and join together around the middle part of development . At this time the ureters move from the mesonephric ducts to the trigone . In males, the base of the bladder lies between the rectum and the pubic symphysis . It is superior to the prostate, and separated from the rectum by the recto - vesical pouch . In females, the bladder sits inferior to the uterus and anterior to the vagina; thus its maximum capacity is lower than in males . It is separated from the uterus by the vesico - uterine pouch . In infants and young children the urinary bladder is in the abdomen even when empty . </P> <P> Urine, excreted by the kidneys, collects in the bladder before disposal by urination (micturition). The urinary bladder usually holds 300 - 350 ml of urine . As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure . Urination is controlled by the pontine micturition center in the brainstem . </P> <P> Bacteriuria is the presence of bacteria in the urine which can indicate a urinary tract infection such as cystitis . </P>

Where is urine stored in the bladder wall