CHAPTEE XXXVIII 



THE URINARY APPARATUS 



THIS consists of the kidneys ; from each a tube called the ureter leads 

 to the bladder, in which the urine is temporarily stored ; from the 

 bladder a duct called the urethra 

 leads to the exterior. 



The Kidneys are situated in the 

 lumbar region of the abdomen on 

 either side of the spinal column 

 behind the peritoneum. In man each 

 is about 4 inches long, and weighs 

 about 4J oz. 



Structure. The kidney is covered 

 by a fibrous capsule, which is slightly 

 attached at its inner surface to the 

 proper substance of the organ by 

 means of very fine bundles of areolar 

 tissue and minute blood - vessels. 

 At the hilus of the kidney it becomes 

 continuous with the external coat of 

 the upper and dilated part of the 

 ureter (fig. 370). 



On dividing the kidney into two 

 equal parts by a section carried 

 through its long convex border, it is 

 seen to be composed of two portions, 

 called respectively cortical and medul- 

 lary ; the latter is composed of about 

 a dozen conical bundles of urinary 

 tubules, each bundle forming what is called a pyramid. The upper 

 part of the ureter is dilated into the pelvis ; and this, again, after 

 separating into two or three principal divisions, is finally subdivided 

 into still smaller portions, varying in number from about 8 to 12, 

 called calyces. Each of these little calyces or cups receives the 

 pointed extremity or papilla of a pyramid. The number of pyramids 

 varies in different animals ; in some there is only one. 



The kidney is a compound tubular gland, and both its cortical 

 and medullary portions are composed of tubes, the tubuli uriniferi, 

 which, by one extremity, in the cortical portion, commence around 



565 



FIG. 370. Kan of a longitudinal section 

 through the pelvis and substance of the 

 right kidney, : a, the cortical sub- 

 stance ; I, b, broad part of the pyramids 

 of Malpighi ; c, c, the divisions of the 

 pelvis named calyces, laid open ; c\ one 

 of those unopened ; d, summit of the 

 pyramid projecting into calyces ; c, e, 

 section of the narrow part of two 

 pyramids near the calyces ; p, pelvis 

 or enlarged portion of the ureter 

 within the kidney ; u, the ureter ; s, the 

 sinus ; h, the hilus. 



