FIG. 1603. 



I'.' 1-VCMd 



Convoluted tubules, cut transversely ami <>t>- 

 liquely, sllouiiiK rharac trr <il epithelial lining. 



I8 8o HUMAN ANATOMY. 



apparent. ** the dOM relations ,,f glomerulus and capsule result from the growth of the latter 

 around tin- vascular tuft and not from invagination of the dilated tubule. The capsule consists 



(,f a distinct membrana propna and a lining composed 

 of a single layer of flat, plate-like cells, the modified 

 epithelium of the uriniferous tubule. In sections pass- 

 ing through the afferent vessel and the neck the lumen 

 Of the capsule appears crescentic in outline, since the 

 space between its outer and inner walls is widest at 

 the neck and reduced to a mere slit where the two 

 layers are continuous around the narrow stalk tra- 

 versed by the afferent and efferent vessels. The inner 

 or "visceral" layer of the capsule, the thicker of the 

 t\\.>, is (irmly attached to the glomerulus by the deli- 

 cate intervening connective tissue, the entire complex 

 appearing rich in nuclei which belong to the epithe- 

 lium of tin- capsule, the endothelium of the capillaries, 

 and the connective-tissue cells. 



2. The Proximal Convoluted Tubule. After un- 

 dergoing the conspicuous constriction marking the 

 neck of the capsule, the uriniferous tubule abruptly 

 enlarges into the convoluted segment which forms ap- 

 proximately one-fifth of the length of the entire canal 

 and has a diameter of from .O4o-.o6o mm. In com- 

 mon with other parts of the tubule, its wall consists of a 

 membrana propria, apparently structureless, but com- 

 posed of a delicate reticulum and intervening homoge- 

 neous substance and a single layer of epithelial tells. 

 Although the histological details of the latter 

 vary in different, but not constant, parts of the convo- 

 luted segment, the lining cells present certain charac- 

 teristics, chief among which is the differentiation of 

 the cytoplasm of the cells into a broader outer and 

 a narrow inner /one. The former exhibits coarse radial striations, the so-called "rods," pro- 

 duced 1>\ rows of granules within the vertically disposed threads of spongioplasm (Rothstein) 

 which occupy approximately the pe- 

 ripheral half of the cell extending 

 from the membrana propria towards 

 the inner /one. The latter, next the 

 lumen, usually appears as a well- 

 defined narrow lx>rder which, when 

 ^flilly preserved, presents a 

 tin'- \ertical striation ("bristle bor- 

 th.n depends not upon rows 

 miles, as (In the rods of the outer 

 /one. but upon the dis|x>sition of 

 the threads of the spongioplasm. In 



< ..llse<|t|e|l. e i ,f lll.ICer.lt joll alld otlleT 



post-nu irtem changes, the inner /one 

 m. iv undergo partial disintegration 

 and break up into slu.rt hair-like rods 

 which h.ive In-en mistaken for cilia. 

 Although the spherical nuclei (.005- 

 iin. i of the epithelium of the 

 convoluted tubule are sharplv de- 

 fined, the demarcations bctueeii the 

 individual i ells an- ol>s. im- .md often 

 wanting, the tubule Ix-ing lined 1>\ a 



se.-millglv ( olltillUolls nucleated laver 

 MI \tllllll. The lumell is iu.t 



uniform throughout the convoluted 



tllbllle. Ill s, . tile places | K -illg U ide alld 



ill otliels reduced t. i Illi-re i lefts; these Blcxxl-v.-s-.i-l 



ditleren.es .l.p.nd chieflv upon the I', .i t ,, ,| nu-.lullary ray, sl.owinj; spiral an.l ,-olK-ctinK tubulos. X 400. 



varv ing height of the epithelial lining. 



; The Spiral Tubule, Following the tortuous path of the convoluted tubule, the canal is 

 usu.ilK continued into the medullarv PJ |.\ a segment u hi, h, while comparatively straight, de- 



FIG. 1604. 



Collecting 

 tubule 



-Spiral tubule 



