2O4 



THE VITAL PROCESSES 



The uriniferous tubules are lined with secreting cells. 

 These differ greatly at different places, but they all rest 



upon a basement membrane and 

 are well supplied with capillaries. 

 These cells provide one means 

 of separating wastes from the 

 blood (Fig. 90). 



Blood Supply to the Kidneys. 

 The method by which the 

 kidneys do their work is sug- 

 gested by the way in which the 

 blood circulates through them. 

 The renal artery entering each 

 kidney divides into four branches 

 and these send smaller divisions 

 to all parts of the kidney. At 

 the outer margin of the kidney, 

 called the cortex, the blood is 



passed through two sets of cap- 

 FIG. 90 Diagram illustrat- illarigSm The first forms the 

 mg renal circulation, i. Branch 



from renal artery. 2. Branch clusters in the Malpighian Cap- 

 from renal vein. 3. Small artery Sules and receives the blood 



branches, one of which enters a directly from the smallest ar- 



Malpighian capsule (O- 6. Small , r~, j r 



. tenes. The second forms a 



vein leaving the capsule and 



branching into the capillaries (7) network around the uriniferous 



which surround the uriniferous tubules and receives the blood 

 tubules. 4. Small veins which which hag passe d from the Cap- 

 receive blood from the second set . . , , 



( -n c T u i u illary clusters into a system ot 



of capillaries. 8. Tubule show- 

 ing lining of secreting cells. small veins (Fig. 90). From the 



last set of capillaries the blood 



is passed into veins which leave the kidneys where the 

 artery branches enter, uniting there to form the main renal 

 veins. 



