Wiktionary
urothelium
n. (context anatomy English) The epithelium of the urinary bladder
Wikipedia
Urothelium
Urothelium (or uroepithelium) is an example of " transitional epithelium". It is the type of epithelium that lines much of the urinary tract including the renal pelvis, the ureters, the bladder, and parts of the urethra.