THE KIDNEY 



441 



pursue a characteristically straight course between the parallel tubules 

 of this region and are known as the arteriolce recta. 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, which 

 leave the parent stem at a 

 wide angle, and pass di- 

 rectly to a renal corpuscle 

 as the afferent artery (ar- 

 tcriole; vas afferens) to its 

 glomerulus. Here it sup- 

 plies the capillary plexus 

 in the manner already de- 

 scribed (page 431). 



Certain of the afferent 

 arterioles are peculiar in 

 that (1) they give off 



sum II branches which supply capillaries directly to the convoluted tubules 

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

 mirabilc 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 



FIG. 407. THE DISTRIBUTION OF THE LEFT RENAL 

 ARTERY. 



Of the six arterise propriae renales, five enter in 

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

 of the calyces, are distributed from the arterial 

 arcade to both cortex and medulla, a, ureter; b, 

 renal artery; c, arteriae propriae renales; d, the dark 

 border is the cortex, within which is the lighter 

 medulla. (After Brodel, from Szymonowicz and 

 MacCallum.) 



