STRUCTURE OF KIDNEY 



245 



The other abdominal organs are in front of or above and 

 below the kidneys, so the natural result of this arrangement is 

 that they are stationary, the only stationary organs in the abdomen, 

 the others all move in respiration, digestion, defecation, micturi- 

 tion, parturition. 



The kidney is hollow, the cavity within being called the sinus. 

 It is covered by a fibrous capsule which also lines the sinus. 



Left kidney 



Left ureter 



Right ureter 



FIG. 162. THE KIDNEYS. (Morris.) 



Structure. A kidney is a mass of minute tubes, the uriniferous 

 tubules lined with epithelial cells, which perform the real work of 

 the organ. At the beginning of each is a bulb-like enlargement, 

 indented to form a deep hollow (Bowman's capsule, Fig. 163) 

 which encloses a tuft of renal capillaries. The capsule and vessels 

 together constitute a Malpighian or renal corpuscle. As the 

 tubule leaves the bulb it twists and turns many times and is called 

 the convoluted tubule. It has a network of blood-vessels around it. 

 The convoluted tube finally becomes straight, and at last several 

 straight ones unite to form a collecting tube which opens into the sinus. 



Malpighian corpuscles and convoluted tubes occupy most of 

 the portion of the kidney near the surface, forming the cortex 



