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Where is urine stored?

The bladder is the common name for the urinary bladder, a hollow muscular organ that stores urine before expelling it from the body. The emptying of the urinary bladder is voluntarily controlled in most human beings and many other mammals. The bladder lies just behind the pubis. Urine drains continuously from the kidneys into the bladder through two tubes called ureters. It leaves the bladder through the urethra, a wider tube that leads out of the body. The place where the bladder and the urethra meet is called the neck of the bladder. A complex arrangement of muscles encircles the bladder neck. This ring, called the urethral sphincter, normally prevents urine from leaving the bladder. The bladder can hold more than 1/2 litre (1 pint) of urine.

We lose around 3 litres (5 pints) of water a day through our skin as sweat, and in our breath and urine. We also get rid of extra salt in sweat and we expel waste carbon dioxide gas when we breathe out.