330 



THE ORGANS 



9. The straight or collecting tubule (Fig. 227,3) has at its commence- 

 ment at the apex of a medullary ray a diameter of from 40 to 50,". 

 As it descends it receives other arched tubules, and increases in 

 diameter until in the ducts of Bellini (Fig. 227, 4) of the papilla it has 

 a diameter of from 200 to 300/^ and a widely open lumen. The 

 epithelium is at first low and gradually increases in height. In the 



^v ^^ 











V'.-'VV:r:-'-:' "V.;-^; 



Fig. 228. — Cross Section Through Cortex of Human Kidney. X60. (Technic 2, 

 p. 338.) a, Convoluted tubules of cortical pyramid; b, interlobular arterj-; c, medullary 

 rays; d, ISIalpighian bodies. 



ducts of Bellini it is of the high columnar type. The cytoplasm of 

 these cells contains comparatively few granules, thus appearing 

 transparent in contrast with the granular cytoplasm of the ascending 

 arms of Henle's loops and of the convoluted tubules. 



Location in kidney 



Cortical labyrinth 



Portion of tubule Epithelium 



Bowman's capsule. . Flat with bulging nuclei. 



Neck Cuboidal, granular. 



First convoluted Pyramidal, granular; large cells 



with granules in rows, 

 giving striated appearance; 

 striated free border; indis- 

 tinct cell outline. 



Second convoluted. . Similar to preceding, but cells 



not so distinctly striated and 

 more regular in shape. 



