Histology and ultrastructure of the urothelium lining the ureter and the renal pelvis in sows.

The histology and ultrastructure of the urothelium lining the ureter and renal pelvis in sows was examined using light microscopy, and scanning and transmission electron microscopy. The epithelium of both the ureter and the renal pelvis were similar and consisted of the basal, the intermediate and the superficial cells. The luminal surface of the superficial cells was characterized by microplicae. Transmission electron microscopy showed that the luminal membrane of these cells showed trilaminar asymmetric unit membrane. Tight junctions linked the lateral parts of the superficial cells, while the intermediate and the basal cells were connected to each other and the basal cells with the basal membrane through desmosomes and hemidesmosomes, respectively. Clusters of mitochondria were observed throughout the urothelium. Unlike that of the basal cells, the Golgi complex and the endoplasmic reticulum were well developed in the superficial and intermediate cells. Lysosomes and vesicles were observed only in the superficial and the intermediate cells. Fine cytoplasmic filaments, although very few in the basal cells, were observed throughout the epithelium. The results are compared and discussed with the findings reported on the urotherlium of other mammalian species and humans.