EXCRETION AND THE EXCRETORY ORGANS 



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from which it is expelled from time to time through (4) an exit 

 tube, the urethra. The general arrangement of these parts, as 



Ua 



FIG. 138. The renal organs, viewed from behind. R, right kidney; A, aorta; 

 Ar, right renal artery; Vc, inferior vena cava; Vr, right renal vein; U, right ureter; 

 Vu, bladder; Ua, commencement of urethra. 



seen from behind, is represented in Fig. 138. The two kidneys, 

 R, lie in the dorsal part of the lumbar region of the abdominal 



