Light micrograph of a cross-sectioned human ureter stained with haematoxylin and eosin. Lining the lumen is the folded mucosa, formed by a transitional epithelium, or urothelium, with several layers of cells and the connective tissue lamina propria. Surrounding this are the muscular layers formed by fascicles of smooth muscle fibres that, unlike in the digestive tube, are not clearly arranged in layers.