Urothelium 1

Urothelium 1 Thin section electron micrograph of luminal plasma membrane of superficial cell of dog urinary bladder. The outer leaflet is thicker than the inner leaflet. The plaques are joined by “hinges” of interplaque plasma membrane (arrowheads), where the membrane is sharply angulated. The intracytoplasmic asymmetric membrane also line fusiform vesicles (V). Cytoplasmic microfilaments (F) are attached to the plasma membrane. The thickness of the asymmetric unit membrane is due to unique membrane proteins that are seen in a freeze fracture electron micrograph (see Urothelium 2).