The 3D structure of the human urinary bladder mucosa: a scanning electron microscopy study

We performed a scanning electron microscopy study on the human urinary bladder tunica mucosa. Specimens from bladder biopsies were treated with OsO4 maceration and 1N NaOH maceration methods prior to SEM observation to disclose the three-dimensional organization of the lamina propria, basal lamina and urothelium. The lamina propria housed a well developed capillary plexus just below the basal lamina; the urothelium presented a typical three-layered organization with basal, intermediate and superficial cells. The intermediate cells appeared essentially similar to basal cells in their external features and stretched from the basal lamina up to the superficial layer. The most superficial cells appeared consistently flattened and interconnected by extensive junctional complexes. They showed a peculiar specialization, their apical plasmalemma being thickened with distinctive, stiff plaques, in contrast with the underlying globular or spindle-shaped cells whose plasmalemma was only covered by short microvillosities.