270 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



outer fibrous, a middle muscular, and an inner mucous 

 layer. The latter has many longitudinal folds and 

 is lined by transitional epithelium of four or five 

 layers of cells. The superficial cells are flat, or low 

 cubical, and may contain two nuclei. Their lower 

 surfaces have depressions that fit upon the rounded 

 ends of the second layer, which consists of oval or 

 pear-shaped cells. Between the apices of the latter 

 are two or three rows of small, irregular interstitial 



cells. Mucous 

 glands have 

 been described 

 in the renal pel- 

 vis and so have 

 lymphoid nod- 

 ules, but the 

 presence of 

 glands in the 

 ureter of man 

 is doubtful. 

 The membrana 

 propria is com- 

 posed of areolar 

 tissue which 

 becomes gradually loose toward the muscularis. This 

 membrane is like others of its kind, having a limited 

 blood supply. The muscular coat is composed of 

 smooth muscle cells and consists chiefly of a circular 

 layer between two thin longitudinal layers, particu- 

 larly well defined in the lower part of the ureter. 

 The fibrous coat is relatively thick and strong, con- 

 tributing fibrous elements that interlace the muscle 

 tissue. 



Fibrous 

 coat. 



Fig. 204. Cross section of the ureter. 



