182 



ELEMENTARY PHYSIOLOGY 



LESS. 



free from granules ; the cells of the ascending limb, 

 though small, are somewhat granular and often striated 

 and thus present attinities to the cells of the convoluted 

 tubules. These two chief types of cells are shown in 

 Fig. 55. 



The artery which supplies the kidney enters at the 

 hilus and divides into branches which pass round the 

 pelvis and proceed outwards between the pyramids. At 



Fig. 55.— Types of the two chief kinds of Cells in the Tubules 

 OF the Kidney. 



A, tubules cut lengthwise ; B, tubules cut across. 

 a, type of (secreting) cell lining the convoluted (spiral and zigzag) 

 tubules ; b, type of cells lining the conducting, collecting and dis- 

 charging tubules ; n, nuclei ; c, in B, capillaries seen in section. 



the junction of the medulla and cortex the.se branches 

 spread out sideways and form arches. From these arches 

 branches run (i) straight out to the surface of the kidney 

 giving off smaller lateral branches, of which some pass to 

 the capsules while others supply the capillary network 

 round the tubules : (ii) down towards the pyramids, in 

 whose substance they break up into capillaries. The 

 veins also form arches at the junction of the cortex and 

 medulla, into which the blood flows from the capillaries, 



