THE KIDNEYS. 



1261 



presents an area along the medial part of its posterior surface adapted to the 

 anterior aspect of the psoas major muscle. .This part of the posterior surface 

 looks medially and slightly posteriorly. More laterally there is a larger area 

 which rests against the quadratus lumborum and looks more directly backwards. 

 These two areas are separated by a rounded ridge which fits into the angle be- 

 tween the muscles mentioned. Beyond the area in contact with the quadratus 

 lumborum is the thick lateral border of the kidney, which rests for the most 

 part on the tendon of the transversus abdominis and on the diaphragm. 



Towards the superior end of the kidney the posterior surface slopes somewhat 

 forwards and rests upon the diaphragm. Indeed the superior part of the kidney 

 is, as a whole, bent slightly forwards, following that part of the arch of the 

 diaphragm on which it rests, and thus a narrow interval is left, in which the pleural 

 cavity passes down behind the superior end of the kidney (Fig. 981). This relation- 



Area for 



diaphragm 



Area for eras of 

 diaphragm 



Area for 

 diaphragm 



Area for 

 quadratus 

 lumborum 



Area for psoas 

 majorf" 



Area for psoas 

 major 



982. THE POSTERIOR ASPECT OP THE KIDNEYS. Same specimen as Fig. 981. The dotted lines mark 

 out the areas in contact with the various muscles forming the posterior abdominal wall. 



a. Depression corresponding to the transverse process of the first lumbar vertebra. 



b. Depression corresponding to the transverse process of the second lumbar vertebra. 



c. Depression corresponding to the twelfth rib. 



ship of the pleural cavity to the kidney is of great importance in connexion with 

 surgical operations performed through a lumbar incision. The portions of the 

 diaphragm to which the kidney is applied are the crus and the parts arising from 

 the last rib and lumbo-costal arches. 



The posterior relationships of the kidney are well seen in Fig. 981. 



In addition to these surfaces, or "facets," for the muscles with which it is in contact, the 

 posterior aspect or lateral border of the kidney often shows a groove for the last rib, another for 

 the lateral lumbo-costal arch, and two or three depressions for the tips of the transverse processes 

 of the upper two or three lumbar vertebrae. In some cases also faint narrow grooves are to be 

 seen for the nerves which pass downwards and laterally between the kidney and quadratus 

 lumborum namely, the last thoracic nerve and the ilio-hypogastric and ilio-inguinal nerves. 



It is probable that some at least of the depressions on the posterior aspect of the kidney are 

 produced after death, and are caused by the weight of the other abdominal organs pressing the 

 kidney backwards against the more resisting structures of the abdominal wall, at a time when 

 the muscles behind the kidney have become flaccid. When much fat is present the posterior 

 aspect of the kidney is more uniformly convex. 



The lateral border in its middle and inferior part is rather a surface than a 

 border, and looks for the most part directly backwards. It rests on the diaphragm 

 and on the anterior surface of the tendon of the transversus abdominis, to the 



