THE UKDttFEKOUS TUBULES 



341 



281. RECONSTRUCTION OF A GLOMERULUS 

 OF THE HUMAN KIDNEY. 



a, afferent vessel ; J, efferent vessel ; c, capillaries. 

 x 444. (After Johnston.) 



1. The Malpighian Body. A Malpighian body consists of a 

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

 course of its development is invaginated into the end of the uri- 

 niferous tubule, and thus 

 comes to be enveloped by 

 a double layer of flattened 

 epithelial cells known as the 

 capsule of Bowman. 



The one layer of Bow- 

 man's capsule, the quasi- 

 visceral, closely invests the 

 entire surface of the glom- 

 erulus except at that point 

 where the afferent and effer- 

 ent vessels enter and leave 

 the capillary tuft; at this 

 point the visceral epithelium 

 is reflected outward and be- 

 comes continuous with the 

 quasi - parietal layer. The 

 surfaces of these two layers 



are almost in apposition; the narrow interval between them 

 which results from the slightly eccentric position of the glomeru- 

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

 At that pole of the Malpighian body which is opposite the en- 

 trance of its blood vessels the capsule opens, through a narrow 

 neck, into the first or proximal convoluted portion of the urinif- 

 erous tubule. 



The glomerulus is a true arterial rete mirabile? since it receives 

 an afferent artery, which, after forming the capillaries of the glom- 

 erulus, passes out as an efferent artery to again enter a capillary 

 plexus about the neighboring tubules of the renal cortex. The 

 afferent vessel is of somewhat larger caliber than the efferent, a 

 noteworthy fact because of its relation to the intraglomerular 

 blood pressure. 



On entering the glomerulus the artery divides into two vessels 

 which immediately subdivide with the formation of five branches 



* Retia mirabilia are formed by the rapid division of a blood vessel, the 

 resulting capillaries being as promptly reunited to form an efferent vessel of 

 the same character as the afferent. Retia mirabilia may be either arterial or 

 venous. 



