KIDNEY 



317 



est being immediately beneath the capsule. Thus a single section of an 

 embryonic kidney shows various stages in the development of the tubules. 

 Sections of the Kidney. Since a radial section of the kidney shows both 

 cortex and medulla, it is the form usually made for pathological examina- 

 tions (Fig. 312). The tubules may be studied to better advantage, 

 however, in tangential sections, one through the cortex and the other 

 through the medulla. The tubules are then seen in cross section. The 



Capsule of the 

 glomerulus 

 (outer layer.) 



Thick segment of 

 the descending 

 limb of Henle's 

 loop. 



Proximal convoluted 

 tubule. 



\ 

 I 



Capillary. 

 Ascending limb of Henles' loop ; 



Collecting tubule. 



FIG. 313. TANGENTIAL SECTION OF THE CORTEX OF A HUMAN KIDNEY. X 200. (Schaper.) 

 The pars radiata is seen in the lower left corner. The line from "capsule of the glomerulus" passes between 



two distal convoluted tubules. 



rays of the cortex appear as islands of circular sections surrounded by the 

 irregular convoluted tubules, among which are the scattered renal cor- 

 puscles. The greater part of such an island is shown in the lower portion 

 of Fig. 313. The renal tubules are lined throughout with simple epithelium 

 and their characteristic features will now be considered, beginning with 

 the glomerular capsule. 



The glomerular capsule (of Bowman) consists of two layers. Its inner 



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