Urothelium lines all of the following renal structures, EXCEPT:
Ureters
Minor calyx
Urinary bladder
Collecting duct
The calyces, renal pelvis, ureter, and bladder have the same basic histologic structure, with the walls becoming gradually thicker closer to the bladder. The mucosa of these organs is lined by unique stratified transitional epithelium or urothelium.The urothelium is composed of the following three layers:A single layer of small basal cells resting on a very thin basement membrane,An intermediate region containing from one to several layers of more columnar cells,A superficial layer of very large, polyhedral or bulbous cells called umbrella cells which are occasionally bi- or multinucleated and are highly differentiated to protect underlying cells against the cytotoxic effects of hypeonic urine.