Urine is stored in an elastic, hollow organ called the urinary bladder. The kidneys produce urine, which passes into the urinary bladder where it is stored until disposal via urination.
The urinary bladder is located on the pelvic floor. It is a distensible organ that changes shape and size according to how much urine it contains. The human bladder is capable of holding an estimated 400 to 600 milliliters of liquid.
The bladder is lined with a layer of transitional epithelium and has folds called rugae. It is capable of expanding due to the rugae folds and the transitional epithelium lining. The bladder also has a submucosa layer made up of elastic fibers and connective tissue. The base of the bladder is called the fundus, and the detrusor muscle is a layer of smooth muscle fibers that prompts the body to dispel urine. The detrusor muscle contracts involuntarily, and having an overactive detrusor muscle causes urinary incontinence.
The bladder allows the storage of urine so that urination is infrequent and controllable. During urination, the bladder muscles contract and urine passes out of the bladder through the urethra. The urethra is longer in men than in women because it passes through the penis.
There are several conditions that can affect the bladder, including bladder cancer, hematuria, cystitis and overactive bladder.