THE URINARY SYSTEM. 



381 



The convoluted, spiral, and zigzag tubules are lined by columnar 

 or cubical cells, the lateral surfaces of which dovetail into each other ; 

 they are very granular, the granules tending to be arranged in rows at 

 right angles to the lumen, so that the cells have a rodded appearance. 

 The descending part of the loop of Henle is lined by clear, flattened 



Bowman's capsule. Neck. 1st convoluted tubule. 



Afferent vessel. 



Efferent vessel. 



Intertubular capillaries. 



Interlobular vein. 



Interlobular artery 

 Spiral tubule. 



Cortical substance. 



Henle's/ Ascending limb. , . -, ',,-,.-*, -nnv/a.----- -~- > * 



loop \ Descending limb. ^ f ,vK?s%&3lltK "^ ^--^>>^ I Boundary zone. 



Arterial arch. 

 Venous arch/ 



Duct of Bellini. 



FIG. 131. Scheme of renal tubule and its vascular supply. 

 (From Gray's Anatomy.} 



epithelium ; the cells of the ascending limb resemble those of the con- 

 voluted tubules. The collecting tubules are lined by clear, cubical 

 cells. Throughout the whole length of the tubules the cells rest upon 

 a well-marked basement membrane. The tubule thus consists of (1) 

 Bowman's capsule, (2) first convoluted and 'spiral tubule, (3) loop of 

 Henle, (4) zigzag and second convoluted tubule, and (5) collecting 

 tubule. 



The Blood Supply. The renal artery enters the kidney close to the 

 origin of the ureter, and divides into branches, which form incomplete 



