THE KIDNEY 



429 



1. Capsule of the renal corpuscle. 



2. K"eck of the tubule. 



3. Proximal convoluted portion. 



4. Descending limb of Henle's loop. 



5. Loop of Henle. Medullary loop. 



6. Ascending limb of Henle's loop. 



7. Distal convoluted portion. 



8. Arched collecting tubule. 



9. Straight collecting tubule. 

 10. Papillary duct. 



It should be borne in mind that all of these several portions form 

 only successive parts of a single uriniferous tubule. Those portions of 

 the urine which are secreted into the capsule of the renal corpuscle 

 must therefore find their way through each of these successive portions 

 before it can reach the excretory passages of the renal calyces, pelvis, 

 and ureter. 



1. The Renal Corpuscle (Malpighian Body). A renal corpuscle 

 consists of a spherical tuft of capillary vessels, the glomerulus, which in 

 the course of its development 

 is invaginated into the end of 

 the uriniferous tubule, and 

 thus comes to be enveloped by 

 a double layer of flattened epi- 

 thelial cells known as the glom- 

 erular capsule (of Bowman). 



The inner visceral layer of 

 the capsule closely invests the 

 entire surface of the glomeru- 

 lus, except at that point where 

 the afferent and efferent vessels 

 enter and leave the capillary 

 tuft; at this point the visceral FlG " 401. -RECONSTRUCTION OF A GLOMER- 



ULUS OF THE HUMAN KIDNEY. 

 epithelium is reflected outward 



and becomes continuous with 

 the parietal layer. The sur- 

 faces of these two layers are almost in apposition ; the narrow interval 

 between them which results from the slightly eccentric position of the 

 glomerulus forms the first portion of the lumen of the uriniferous tubule. 

 At that pole of the renal corpuscle which is opposite the entrance of its 



a, afferent arteriole; b, efferent arteriole; 

 c, capillaries. X 444. (After Johnston.) 



