RESPIRATION AND EXCRETION 



the points of the pyramids into the calices of the pelvis. 

 They extend back through the medulla and convolute 

 or wind about in the cortex. Here they form multitudes 

 of tiny capsules which surround a network of capillaries. 

 The branches of the renal artery pass into the connective tis- 

 sue of the cortex, giving off a few branches to the pyramids. 



FIG. 177. Longitudinal section through the kidney, (pelvis and a number 

 of renal calices). U, ureter; C, cortex; M, medulla; P, pelvis; 

 T, tubules; B, blood vessel (arterial branch); R. V., branch of renal 

 vein; R. A, branch of renal artery. O, O, pyramids. (Tyson after 

 Henley.) 



Then a branch enters each tiny capsule where it breaks up 

 into a little ball of capillaries called a glomerulus. From the 

 glomerulus a tiny vein passes to the tubules and there again 

 breaks up into capillaries. This network of capillaries finally 

 becomes the branches of the renal vein. These leave the 

 kidney to carry the blood back again to the heart by way 

 of the vena cava ascending. 



