1242 



UROGENITAL SYSTEM 



than the lower [extremitas inferior] and is about 1 cm. nearer the median sagittal 

 plane of the body, owing to the long axis of the organ being directed obliquely 

 downward and laterally. The lateral border [margo lateralis] is narrow and con- 

 vex, and the medial border [margo medialis], which looks medially and ventrally, 

 is concave, its middle third presenting a slit-like aperture, the hilus. This opens 

 into a cavity, called the sinus (fig. 1006), which is about 2.5 cm. in depth and is 

 occupied mainly by the dilated upper extremity of the ureter, known as the renal 

 pelvis, the interval between this and the actual kidney substance containing adi- 

 pose tissue in which are imbedded the renal vessels and nerves. 



Size. — The length of the kidney in the male averages 10-12 cm., its breadth about 5.5 cm. 

 and its thickness 3 cm.; it weighs 115-150 grams. The dimensions of the female kidney are 

 nearly as great, but its weight is from one-seventh to one-fifth less. In the child the organ is 

 relatively large, its weight compared with that of the entire body being about 1: 133 at birth; 

 but its permanent relation, which is about 1:217, is usually attamed at the end of the tenth 

 year. 



Fig. 1005. — Diagr.\m showing Relation of Kidney to Capsule. (Gerota.) 



Aorta 

 Ureter 



Pararenal adipose- 

 body 



Aponeurosis of trans- 

 versus abdominis 



Fascia of quadratus 

 lumborum 



Renal fascia (posterior layer) Fascia of psoas 



Investment and fixation. — The surfa('(^ of the kidney is covered by a thin but 

 strong fibrous capsule [tunica fibrosa], which turns inward at the hilus to line the 

 walls of the sinus (fig. 1006). It may readily be peeled off from a healthy kidney, 

 except at the bottom of the sinus, where it is adherent to the blood-vessels entering 

 the kidney substance and to the terminal portions of the pelvis. External to 

 the capsule is a quantity of fat ti.ssue, the adipose capsule [capsula adiposa], 

 which forms a comph'te investment for the organ and is i)rolongcd through the 

 hilus into the sinus. 



'J'he peritoneum, which covers tlie ventral surface of the adipose capsule, has 

 usually been regarded as the ])rin('i{)al means of fixation of the kidney, but in 

 reality this is accomplished by means of a si)ecial renal fascia (fig. 1005), developed 

 from the subperitoneal areolar tissue (Gerota). 



Renal fascia. — Lateral to the kidney there occurs l)etwcen the transversalis fascia and the 

 peritoiicuiri a subperitoneal fascia, which, as it approaches the convex border of the kidney, 

 divides into two layers, one of which j)asses in front of and the other behind the kidney, enclos- 

 ing the adipose capsule. Traced medially, the anterior layer of the renal fascia passes in front 



