Mucous membrane (mucosa)—transitional epithelium; lines the renal pelvis, ureters, bladder, and urethra.
Epithelial layer—contains no blood vessels or lymphatics.
Basement membrane—lies beneath the epithelial layer; single layer of cells separating the epithelial layer from the lamina propria; a sheet of extracellular material serving as a filtration barrier and supporting structure for the mucosal layer.
Submucous coat (lamina propria)—areolar connective tissue; interlaced with the muscular coat. This layer contains blood vessels, nerves, and in some regions, glands. A tumor which has spread to this layer can metastasize to the rest of the body via the lymphatics and blood vessels.
Muscular coat (muscularis propria)—three layers: inner longitudinal, middle circular, and outer longitudinal.
Adventitia—in areas on kidney and ureter where there is no serosa, the connective tissue between organs merges to become adventitia.
Regional diathesis, field defect—terms which mean a tendency for the lining of the urinary tract to develop multiple tumors; a generalized deterioration of the urothelium from the renal pelvis into the urethra showing premalignant changes. There is a 75% likelihood of subsequent bladder cancer with a diagnosis of diffuse upper urinary tract diathesis (involving both renal pelvis and ureter).