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CHAPTER XIX 

 THE URINARY SYSTEM 



THIS system includes the kidneys, which are two large secret- 

 ing glands, together with their excretory passages, the ureters, 

 which conduct the urine to the urinary bladder, whence it is 

 voided through the urethra. 



THE KIDNEY 



Each kidney is a large secreting gland of the compound tubu- 

 lar type. Its secretion, the urine, is produced by the uriniferous 

 tubules, which are long tortuous canals beginning near the surface 

 of the kidney and finally ending at the hilum of the organ where 

 they pour their secretion into the calyces of the renal pelvis. The 

 uriniferous tubules are in intimate relation with the renal blood- 

 vessels which supply rich capillary plexuses to the entire extent of 

 the tubules. Each uriniferous tubule consists of both tortuous 

 and straight portions, and these are so regularly disposed as to 

 produce macroscopical variations in the appearance of the differ- 

 ent portions of the renal parenchyma according as the tortuous or 

 the straight portions of the tubules predominate. These varia- 

 tions result in the following topographical subdivisions. 



TOPOGRAPHY OF THE KIDNEY (Figs. 288 and 290). If the 

 kidney be divided parallel to its long axis by an incision extending 

 from its convex surface to the hilum, the cut surface shows that 

 the parenchyma is divisible into a superficial cortex and a central 

 medulla. The hilum of the organ forms a deep excavation which 

 is occupied by the renal pelvis and its subdivisions, the infundiv- 

 ula and calyces, into which the medulla projects in the form of 

 several conical pyramids. The pelvis of the kidney, the expanded 

 funnelform beginning of the ureter, toward the renal parenchyma 

 divides into two or three infundibula, which in turn subdivide 

 into several calyces, each of which incloses the conical apex of a 

 projecting medullary or Malpighian pyramid. 



