 So transitional epithelium is a special type of epithelium that's found in the urinary bladder and the urethra. Of course the urinary bladder stores urine and as the urine fills up the bladder, the bladder has to be able to expand. When the bladder is empty, transitional epithelium appears to have many different layers. But as the bladder stores more and more urine, the number of layers in transitional epithelium appears to decrease. So this tissue is called transitional epithelium because it's able to undergo transitions as the bladder fills and empties.