THE URINARY ORGANS. 



CHAPTER XI. 



THE URINARY ORGANS. 



THE KIDNEY. 



THE kidney is a highly-developed compound tubular gland, com- 

 posed of pyramidal lobules which correspond in number with the 

 renal papillae and Malpighian pyramids : in the adult, however, their 

 distinctness is lost, since 



they become blended to- FlG - 234 ~ 



gether. On laying open * 



the fresh organ by a 

 longitudinal section, 

 two regions are ap- 

 preciable, the cortex 

 and the medulla. The 

 cortex is readily distin- 

 guished as the periph- 

 eral granular zone em- 

 bracing the outer third, 

 while the medulla ap- 

 pears radially striated 

 and occupies the re- 

 maining two-thirds of 

 the gland. 



The inner surface of 

 the medulla, next the 

 pelvis, presents a num- 

 ber of eminences, or 

 papillae, at whose apices 

 open the large terminal 

 uriniferous tubules or 

 excretory ducts. Each 

 renal papilla is the cul- 

 minating point of a sys- 

 tem of dividing and sub- 

 dividing tubules, which 

 collectively form a pyramidal mass, the base of which corresponds 

 to the surface of the organ, while its apex is the papilla. These 

 pyramidal tracts constitute the lobules of which the kidney is com- 



Longitudinal section of human kidney, exhibiting general 

 relations of macroscopic details: A, renal artery; U, ureter ; 

 C, one of the calices into which a papilla projects; i, cortex 

 containing labyrinth (/) and medullary rays (m) ; 2, medulla ; 

 M, Malpighian pyramids, some obliquely cut at 3 ; b, bound- 

 ary layer; S, columns of Bertini ; 4, masses of adipose tissue; 

 5, branches of renal artery. (After Ifenle.) 



