THE URETERS 



1247 



tubule, which occupies the axis of the medullary ray. Then, descending into the subjacent 

 medullary pyramid, it unites with other collecting tubules, and finally opens into the renal pelvis 

 at the summit of a papilla. 



The tubules are lined with epithelium throughout, the cells being tesselated in the capsule, 

 irregularly cubical in the convoluted tubules and ascending limbs, flattened on the descending 

 limbs and loops of Henle, and columnar in the cortical collecting tubules and in the straight 

 tubules of the medulla. 



Vessels (fig. 1011).^ — The kidney is very vascular. The larger arterial branches, aTranged 

 in the sinus as has ah-eady been described, enter the substance of the kidney and pass up as the 

 interlobar arteries in the renal columns. On reaching the bases of the pyramids they bend so as 

 to run horizontally between these and the cortex, forming the arcuate arteries [arteriae arciformes] 

 from which interlobular branches pass up into the cortex and supply afferent branches to the 

 Malpighian glomeruh. From the arcuate arteries numerous branches, the arteriolce rectces, 



Fig. 1011. — Scheme of Tubules and Vessels op the Kidney. 



Fibrous capsule - 

 Cortical vein ' 



Renal corpuscle 



Cortexi -< 



Cortical vein 

 Arcuate artery 



Medullary artery 



Efferent vessel 



forming medullary 



plexus 



Medulla < 



Papillary plexus 

 surrounding the ^ 

 foramina papillaria 



Second convoluted 

 tube 



■Renal corpuscle 



First convoluted 

 tube 



Looped tube of 

 Henle 



Duct of Bellini open- 

 ing at the fora- 

 men papillare 



pass down mto the pyramids, supplying the tubules of which these are composed. Efferent 

 stems which issue from the Malpighian glomeruli break up into capillaries which supply the 

 tubules contained in the cortex. Veins corresponding to the arteriolae recta; and to the inter- 

 lobular, arcuate and interlobar arteries occur, opening into the renal veins, and, at the surface 

 of the kidney, arranged in star-hke groups, are the stellate veins [vena stellatte], which open 

 into the interlobular veins and also communicate with the veins of the adipose capsule. The 

 renal lymphatics may be divided into two sets, capsular and parenchymatous. They terminate 

 in the upper lumbar nodes. 



Nerves. — The nerves form a plexus accompanying the vessels, and are derived from the 

 sympathetic and vagus through the renal plexuses. 



Variations.— The kidney of a foetus differs from that of the adult in being divided into a 

 number of distinct renal lobes, each of which corresponds to the base of a renal pyramid and 



