992 



THE URINARY ORGANS. 



The Renal Blood-vessels. The kidney is plentifully supplied with blood by 

 the renal artery, a large offset of the abdominal aorta. Previously to entering 

 the kidney, each artery divides into four or five branches, which are distributed 

 to its substance. At the hilum these branches lie between the renal vein and 

 ureter, the vein being in front, the ureter behind. Each vessel gives off some 

 small branches to the suprarenal capsules, the ureter, and the surround- 

 ing cellular tissue and muscles. Frequently there is a second renal artery, 

 which is given off from the abdominal aorta at a lower level, and supplies the 

 lower portion of the kidney. It is termed the inferior renal artery. The 

 branches of the renal artery whilst in the sinus give off a few twigs for the 

 nutrition of the surrounding tissues, and terminate in the arterice proprice renales, 

 which enter the kidney proper in the columns of Bertin. Two of these pass 

 to each pyramid of Malpighi and run along its sides for its entire length, 

 giving off as they advance the afferent vessels of the Malpighian bodies in the 

 columns. Having arrived at the bases of the pyramids, they make a bend in 

 their course, so as to lie between the bases of the pyramids and the cortical arches, 

 where they break up into two distinct sets of branches devoted to the supply of the 

 remaining portions of the kidney. 



The first set, the interlobular arteries (Figs. 551, 552, B), are given off at right 



angles from the side of the arteriae proprise 

 renales looking toward the cortical substance, 

 and, passing directly outward between the pyra- 

 mids of Ferrein, they reach the capsule, where 

 they terminate in the capillary network of 

 this part. In their outward course they give 

 off lateral branches ; these are the afferent ves- 

 sels for the Malpighian bodies (see page 988), 

 and, having pierced the capsule, end in the 

 Malpighian tufts. From each tuft the corre- 

 sponding renal efferent arises, and, having made 

 its egress from the capsule near to the point 

 where the afferent vessel entered, breaks up 

 into a number of branches which form a dense 

 venous plexus around the adjacent urinary 

 tubes (Fig. 553). 



The second set of branches from the arteriae 

 propriae renales are for the supply of the medul- 

 lary pyramids, which they enter at their bases ; 



FIG. 553. Diagrammatic representation 

 of the blood-vessels in the substance of the 

 cortex of the kidney, m. Region of the 

 medullary ray. b. Region of the tortuous 

 portion of the tubules, at. Arteria inter- 

 lobnlaris. vi. Vena interlobularis. va. Vas 

 afferens. gl. Glomerulus. ve. Vas efterens. -, - - . . -, t \ 



rz. Venous twig of the interlobularis. (From and, passing straight through their substance 



Ludvvig, in Strieker's Handbook.) , i i, 



to their apices, terminate m the venous plex- 

 uses found in that situation. They are called the arteriolce rectce (Figs. 551, 

 552, F). 



The renal veins arise from three sources the veins beneath the capsule, the 

 plexuses around the convoluted tubules in the cortical arches, and the plexuses 

 situated at the apices of the pyramids of Malpighi. The veins beneath the capsule 

 are stellate in arrangement, and are derived from the capillary network of the 

 capsule, into which the terminal branches of the interlobular arteries break up. 

 These join to form the vence interlobular es, which pass inward between the pyramids 

 of Ferrein, receive branches from the plexuses around the convoluted tubules, 

 and, having arrived at the bases of the Malpighian pyramids, join with the venae 

 rectse, next to be described (Figs. 551, 552, V). 



The Vence Rectce are branches from the plexuses at the apices of the medullary 

 pyramids, formed by the terminations of the arteriolse rectae. They pass outward 

 in a straight course between the tubes of the medullary structure, and joining, as 

 above stated, the venae interlobulares, form the proper renal veins (Figs. 551, 552, /). 



These vessels, Vena? Proprice Renales, accompany the arteries of the same name, 

 running along the entire length of the sides of the pyramids ; and, having received 



