FUNCTIONS OF THE KIDNEY 



85 



tention calls for relief, and the uretlira, or tube, or duct, 

 of the bladder through which the urine is voided. 



The kidney is a compound tubular gland which, when 

 split from outer to inner border, is seen to consist of an 

 outer or cortical portion; an inner pyramidal or medul- 

 lary portion and a deep concavity, the Jiilum, filled by 



Fig. 19. Longitudinal section through the kidney: /, Cortex; i' , med- 

 ullary rays; i" , labyrinth; 2. medulla; 2', papillary portion of medulla; 

 2", boundary layer of medulla; 3, transverse section of tubules in the 

 boundary layer; 4, fat of renal sinus; 5, artery; *, transverse medullary 

 rays; A, branch of renal artery; C, renal calyx; U, ureter (after Tyson and 

 Henle). 



blood vessels and the pelvis or beginning of the ureter. 

 The cortical area, about two-thirds of the organ, is the 

 active, secretory portion of the kidney, the remainder 

 being the collecting area. In the cortical portion are 

 found the glomeruli and convoluted tubules which re- 

 move the urine from the blood, while in the medullary 



