The bladder is a storage organ that sits in your pelvis. Urine is made by your kidneys and stored in the bladder until you are ready to empty it. When you go to the toilet your bladder outlet muscles (urethral sphincter and pelvic floor) relax and your bladder contracts (squeezes) emptying your bladder of urine. Your brain controls your bladder by sending messages to tell it when to hold on and when to empty.
Male pelvis anatomy
Female pelvis anatomy
A normal bladder:
People who experience accidental or involuntary loss of urine from the bladder may be suffering from urinary incontinence.