1352 



THE URINOGENITAL ORGANS 



The cortex is reddish brown in color and soft and granular in consistence. It lies imme- 

 diately beneath the capsule, arches over the bases of the pyramids, and dips in between adjacent 

 pyramids toward the renal sinus in the form of renal columns (columnae renales [Bertini]). If 

 a section of the cortex be examined with a lens, it will be seen to consist of a series of lighter 

 colored, ray-like prolongations of straight tubules from the medulla, called the medullary rays 

 (pars radiata). The darker colored intervening substance composing the remainder of the 

 cortex, from the complexity of its structure, is called the labyrinth (pars convoluta), and contains 

 the convoluted portions of the uriniferous tubules and the Malpighian corpuscles. The medul- 

 lary rays gradually taper toward the circumference of the kidney, but do not reach the capsule. 



The medulla consists of reddish, striated, conical masses, the medullary pyramids (pyramides 

 renales [Malpighii]), the number of which, varying from ten to twenty, corresponds to the number 

 of lobes of which the organ is composed in the fetal state. The pyramids are composed of 

 straight tubes which pass from the base to the apex. The sides of the pyramids are contiguous 

 with the renal columns, while the apices, known as the renal papillae, project into the minor 

 calices of the ureteral pelvis, each calix receiving one, two, or three papillae. Each papilla shows 



Boivman's 

 capsule, 

 outer layer 



Blood- 



Beginning of 



urinary 



tubule 



Convoluted 

 tubules 



FIG. 1097. A section through the cortex of an ape's kidney. A Malpighian corpuscle, together with the 

 beginning of the tubule, is shown. X 350. (Szymonowicz.) 



upon its apex a number (16 to 20) of minute orifices of the excretory ducts of the pyramid; this 

 perforated area of the apex is called the area cribrosa (Fig. 1095). 



The renal columns (of Bertin) separate the pyramids from one another and consist of cortical 

 masses extending toward the renal sinus. At the sinus ends they contain a considerable amount 

 of white fibrous and adipose tissue. They serve as a passageway for the main bloodvessels, 

 lymphatics, and nerves to and from the parenchyma of the organ. 



Minute Anatomy. The uriniferous tubules (tubuli renales) are in part very convoluted 

 and in part straight and regular. They arise in the cortex, pass into the medulla, return to the 

 cortex, and end at the area cribrosa of the renal papilla. Each tubule starts at the glomerulus 

 or renal corpuscle (Malpighian body), a small, round, reddish mass, which measures 120 to 

 200 //. Each of these little bodies is composed of two parts, a central glomerulus of vessels, 

 called a Malpighian tuft and a membranous envelope, the Malpighian capsule, or capsule of 

 Bowman, which is the small pouch-like commencement of a uriniferous tubule. 



The Malpighian tuft, or vascular glomerulus, is a network of convoluted capillary bloodvessels, 

 held together by scanty connective tissue. This capillary network is derived from a small arterial 

 twig, the afferent vessel, which pierces the wall of the capsule, generally at a point opposite to 

 that at which the latter is connected with the tube; and the resulting vein, the efferent vessel, 



