METABOLISM AND TRANSPORT IN ANIMALS 



539 



Convoluted tubule 



Renal f Bowman's capsule — 

 corpuscle' Glomerulus 



Median section of kidney 



Cortex 



Cortex with 

 renal corpuscles 



Loop of Henle 

 Pyramid of 



medulla containing 

 collecting tubules 

 Renal artery 



Renal vein 

 Pelvis 



Medu 



Collecting 

 tubule 



Ureter 



Tip of pyramid 



Detail of renal 

 corpuscle and 

 collecting tubule 



Figure 390. Excretory system of man. Upper left, diagram of entire system. Lower left, kidney 

 in median section. Right, relations of renal corpuscle tubules, and blood vessels. Solid arrows, 

 path of blood; dotted arrows, path of excretion. 



glucose, pus, and blood. A urine analysis is 

 an index of bodily function and is of great 

 assistance in medical diagnosis. 



Although both kidneys are needed to 

 eliminate the wastes of a pregnant woman, 

 a kidney may be removed from certain indi- 

 viduals, with the remaining one ridding the 

 body of metabolic wastes satisfactorily. 



SECRETIONS 



Secretions are substances that are manu- 

 factured by the protoplasm within certain 

 cells and are used by the cells that synthesize 



them, or they are discharged from the cells 

 and used elsewhere in the body. During se- 

 cretion, oxygen is used up and carbon diox- 

 ide is produced, indicating that the process 

 requires the energy liberated by oxidation. 

 Secretory cells may discharge their products 

 continuously or store them until the proper 

 stimulus brings about their discharge at one 

 time. Usually these specialized cells contain 

 visible secretory granules. In some cases it 

 is difficult to distinguish between secretions 

 and excretions, but usually the former are of 

 use to the body, and the latter are waste 

 products that would bring about the death 

 of the animal if they were not eliminated. 



