Figure 1924

Transmission electron micrograph of the apical portion of a transitional epithelial cell. a. The cytoplasm displays small vesicles, filaments, and mitochondria, but the most distinctive feature of the cell is its fusiform vesicles (FV). x27,000. b. The higher magnification shows that the membrane forming the vesicles appears to be similar to the plasma membrane of the cell surface (arrows). Both membranes are thickened and give the impression of possessing a degree of rigidity greater than that of plasma membrane in other locations. The thickened plasma membrane represents a sectioned view of a surface plaque. The fusiform vesicles are formed by the infolding of the plaques in the cells of the relaxed urinary bladder, x 60,000.

smooth muscle move the urine from the minor calyces through the ureter to the bladder.

Ureters

Each ureter conducts urine from the renal pelvis to the urinary bladder and is approximately 24 to 34 cm long. The distal part of the ureter enters the urinary bladder and follows an oblique path through the wall of the bladder. Transitional epithelium (urothelium) lines the luminal surface of interplaque interplaque

interplaque region
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