The superficial cells are rounded and bulge into the lumen. This ureter was sectioned when empty. When the ureter fills, the folds expand. When the ureter is stretched, the epithelium is only three or four cells in thickness and the superficial cells become squamous. This allows the ureter, and especially the bladder, to change volume without rupturing the epithelium.
Some researchers believe that each epithelial cell extends to the basal lamina.
You are here to find macrophages. It has an irregular shape and several basophilic granules of various sizes. Notice also a neutrophil and a lymphocyte in this view. This one has phagocytosed two erythrocytes, which appear as large, darkly stained bodies. On your own explore other links to find additional examples of macrophages.