i884 



HUMAN ANATOMY. 



Fig. 



1611. 



Two calyces 



Superior division 

 of pelvis 



Blood- Vessels. — Arteries. — The renal arteries — usually one to each kidney, 

 but not infrequently two, and in exceptional cases three or even four — are of unequal 

 length, the right one being the longer in consequence of the parent stem, the aorta, 

 lying to the left of the mid-line. Embedded within the subperitoneal tissue and 

 covered by the renal fascia (page 1872), they pass laterally, accompanied and more 

 or less masked by the renal veins, to the hilum of the kidney, during their course 

 giving of! small twigs to the capsula adiposa as well as to the suprarenal bodies. 

 Just before entering the kidney, or within the hilum, the renal artery divides into an 

 anterior (ventral) and a posterior (dorsal) branch, each of which embraces the pel- 

 vis and divides into four or five twigs that hug their respective wall of the sinus. 

 Preparatory to entering the kidney, each twig breaks up into from three to five 



smaller divisions which enter the 

 renal substance through the vascu- 

 lar foramina surrounding the pa- 

 pillae. On entering, they pass 

 along the sides of the papillae, their 

 course corresponding in position to 

 the original tracts of connective tis- 

 sue that separate the primary di- 

 visions of the foetal kidney (page 

 1876) ; they are therefore appro- 

 priately designated interlobar ar- 

 teries. The general expansion of 

 the branches derived from the an- 

 terior and posterior arteries is par- 

 allel to the corresponding ventral 

 and dorsal surfaces of the kidney ; 

 the intervening zone along the 

 convex border of the organ, about 

 I cm. on the posterior surface, 

 contains few, if any, of the larger 

 vessels and, in consequence, ap- 

 pears lighter in color. The vessels 

 supplying the kidney do not anas- 

 tomose, each such ' ' end ' ' artery 

 providing for a particular area of 

 renal substance. On reaching the 

 level of the bases of the renal 

 pyramids, each interlobar artery 

 breaks up into a tree-like bundle 

 of twigs, some of which pursue an 

 arched course across the bases of 

 the pyramids, thereby producing 

 the impression of a series of arcades 

 at the junction of the medulla and cortex. From these vessels two series of terminal 

 branches arise, one for the supply of the cortex, the other for that of the medulla. 



Inferior division of pelvis 



Ureter. 



Corrosion preparation of injected right kidney, 

 viewed from behind, showing relations of branches of 

 renal artery to divisions of renal pelvis. 



The cortical arterioles pursue a course generally perpendicular to the free surface, towards 

 which they run between the cortical lobules, giving off short lateral twigs that end as the vasa 

 afTerentia in the glomeruli of the Malpighian bodies. The latter are arranged in colunuis in 

 correspondence with the path of the interlobular cortical arterioles. Some of these, however, 

 do not give off vasa afferentia, but ascend to the kidney capsule, for the supply of which they 

 provide in conjunction with the direct branches from the renal artery. 



After traversing the capillary complex, the blood is carried from the glomerulus by the 

 vas ef?erens, which, smaller than the vas afferens, on its exit immediately breaks up into the 

 cortical capillaries that form net-works enclosing the tubules within the labyrinth, and, continuing, 

 surround those within the medullary ray, in the latter situation the meshes being relatively longer 

 and more open and containing blood that has already .supplied the proper uriniferous tubules. 



The medullary arterioles, derived in part from the terminal branches of the interlobar 

 stems at the bases of the pyramids, descend within the latter as bundles of radially disposed 



