Our bladder stores urine until you're ready to go to the toilet. Urine forms into thin tubes called ureters. Each kidney is joined to your bladder by a ureter.
Our bladder is like a ballon with muscles. It expands as it fills with urine, and contracts when you go to the toilet.
An adult bladder can hold between 300 and 500 millilitres of urine. Whm it's full, the muscular walls contract and force urine through a tube called urethra. An adult makes about 1.5 litres of urine a day. That's enough to fill two and half milk bottles. Because bladders expand and contract without bursting, they've had some strange jobs in the past. Some animal bladders have been used as bagpipes and water floats.