The bladder is a hollow, muscular, balloon-like organ with a flexible, muscular wall that collects and stores urine. It is found in the lower part of the abdomen (the pelvis).
The position of the bladder. Copyright © Pacific Edge Limited
The inside of the bladder is covered with a urine-proof lining (called the urothelium) which stops urine being absorbed back into the body. The cells of this lining are called transitional cells or urothelial cells.
Our kidneys produce urine, which is carried to the bladder by thin tubes called ureters, the bladder then collects and stores the urine. When the bladder is full, the muscles in the bladder wall tighten to get rid of the urine through another fine tube called the urethra. In women, the urethra is a very short tube that ends just in front of the vagina. In men, the urethra is longer. It passes through the prostate gland and the penis, and ends at the tip of the penis.