Urine is produced by the kidneys, drained through the ureters, stored in the bladder and expelled through the urethra.
Urine is held in by different muscles, which keep the urethra closed. When the bladder is full, stimuli are sent to the brain to urinate. The fuller the bladder, the greater the pressure inside it and the greater the effort required to contain the urine.
When we urinate, the bladder muscles contracts, squeezing the bladder and expelling the volume of urine inside. Meanwhile, our muscles relax allowing the urethra to open and the urine to be expelled.
Controlling loss of urine, like urinating, depends on the proper functioning and synchronisation of the bladder and urethra nerves and muscles.