The bladder is a hollow, muscular, balloon-like organ that collects and stores urine. It sits in the lower part of the pelvis (the lower tummy area in between the hip bones).
The inside of the bladder is covered with a urine-proof lining called the urothelium. This lining stops urine being absorbed back into the body.
Urine is produced by the kidneys and travels to the bladder through tubes called ureters. The bladder stores the urine, which is made up of water and waste products that the body doesn’t need.
When the bladder is full, it sends messages (nerve signals) to the brain so that you feel the need to empty your bladder. The bladder muscle contracts and squeezes the urine out of the body through the urethra. The urethra is a short tube that lies in front of the vagina in women. In men, it passes through the prostate gland to the tip of the penis.