THE KIDNEY 



111 



pursue a characteristically straight course between the parallel tubules 

 of this region and are known as the arli'riolir r<>cl'. They branch freely 

 at acute angles and form a rich capillary plexus in the boundary zone, 

 the longest of the vessels reaching beyond the limits of this region to 

 supply a less abundant 

 plexus to the papillary 

 zone of the medulla. 



The cortical branches 

 of the arterial arcades are 

 vessels of considerable size 

 which enter the labyrinth 

 between the cortical rays 

 and as interlobular arteries 

 (cortical arterioles) pass 

 toward the surface of the 

 organ, a few of the longest 

 branches reaching the fi- 

 brous capsule with whose 

 vessels they anastomose. 

 Throughout their whole 

 course the interlobular ar- 

 teries give off numerous 

 short branches, w h i c h 

 leave the parent stem at a 

 wide angle, and pass di- 

 rectly to a renal corpuscle 

 as the afferent artery (ar- 

 teriole; vas afferens) to its 

 glomerulus. Here it sup- 



FIG. 407.- 



DISTRIBUTION OF THE LEFT RENAL 



ARTERY. 



Of the six arterise propria- renales, five enter in 

 front of the renal pelvis, and, lying upon the wall 

 plies the capillary plexus O f the calyces, are distributed from the arterial 

 ill the manner already de- arcade to both cortex and medulla. <i, ureter; b, 



renal artery; c, arteria? propria- renales; <i, the dark 

 border is the cortex, within which is the lighter 

 medulla. (After Brodel, from Szymonowicz and 

 MacCallum.) 



scribed (page 431). 



Certain of the afferent 

 arterioles are peculiar in 

 that (1) they give off 



small branches which supply capillaries directly to the convoluted tubules 

 of the cortical labyrinth; and (2) they occasionally form a small rete 

 mirabile before they reach the glomerulus. By far the greater portion 

 of the branches of the interlobular arteries, however, pass directly to the 

 glomeruli. The capillaries of the glomerulus reunite to form an efferent 



