164 



NORMAL HISTOLOGY. 



interlaced with smooth muscular fibres, outside of which is the 

 external coat of fibrous tissue. 



3. The ureters closely resemble in structure the pelvis of the 

 kidney; but the muscular fibres have a somewhat more definite 

 arrangement, being disposed in an inner imperfect coat of longi- 

 tudinal and an external layer of circular fibres, outside of which 

 a few supplementary longitudinal fibres are, here and there, added 

 (Fig. 141). 



4. The bladder also has a lining of transitional epithelium (Fig. 



FIG. 141. 



Epithelial cells from the human ureter. (Rieder.) 



40), beneath which is a layer of fibrous tissue resembling that of 

 the renal pelvis, but of greater thickness. The muscular coat, 

 which comes next, is thick and composed of bundles of smooth 

 muscular fibres, interlacing in various directions or disposed in 

 more or less well-defined strata. External to the muscular coat 

 is a fibrous coat, which is covered by a reflection of the peritoneum 

 for a part of its extent, and in other situations passes into the sur- 

 rounding areolar tissue. 



The spear-shaped cells of the transitional epithelium of the blad- 

 der have thicker processes than those of the pelvis or ureter ; but 

 when detached and macerated in the urine it is often very difficult 

 to determine from their appearance from what part of the urinary 

 tract such cells were derived (Figs. 142 and 143). 



