The; Urinoge;nital Systiim. 127 



VI. THE URINOGENITAL SYvSTEM. 



A. The Urinary Organs. 



The central organs of excretion, the kidneys (renes), occupy an 

 anterior position on the dorsal wall of the abdomen. The right kidney 

 is placed a little farther forward than the left, and is largely covered by 

 the right posterior lobule of the liver. In addition to a fibrous coat 

 immediately surrounding the kidney substance, each organ is imbedded, 

 in a mass of fatty material, the adipose capsule (capsula adiposa), and 

 is also held in position by the peritoneum, which is stretched across its 

 ventral surface. 



1. By removing the peritoneum and adipose capsule from the left 

 kidney, the external features and vascular connections may be made 

 out as follows: 



(a) The general convexity of contour. 



(b) The renal hilus (hilus renalis), a concavity of the medial sur- 

 face of the organ. 



(c) The ureter, or duct of the kidney, a white tube passing back- 

 ward from the hilus. 



(d) The renal artery (a. renalis), arising from the abdominal 

 aorta and entering the kidney at the hilus. A branch of this 

 vessel, the twelfth intercostal artery (a. intercostalis xii), 

 passes to the body- wall in front of the kidney, giving off a 

 small suprarenal artery to the suprarenal gland. 



(e) The renal vein (v. renalis), leaving the kidney at the hilus, 

 and joining the inferior cava. 



2. Divide the kidney, beginning the incision at the hilus and re- 

 moving the ventral half. Examine the cut surface of the dorsal half for 

 the following: 



(a) The renal pelvis (pelvis renalis), formed by the expanded 

 funnel-like end of the ureter, which is fitted into the renal 

 hilus. The enclosed space is largely occupied by a conical 

 projection of the kidney substance, the renal papilla (papilla 

 renalis). 



(b) The cortical substance (substantia corticalis) ; distinguish- 

 able as a narrow peripheral zone of the kidney substance. 



(c) The medullary substance (substantia medullaris), forming 

 the central and medial portion of the kidney, including the 

 renal papilla. It is distinguished by its radial striations. 



(d) The fibrous coat (tunica fibrosa) of the kidney may be 

 stripped from the surface. 



In the rabbit tlie kidney is not lobulated. Hence there is a single 

 renal papilla, and the division of the kidney substance into renal pyramids 

 is imperfectly expressed. The medullary substance, however, possesses 

 a slightly divided margin. 



