8tS 



A MANUAL OF ANATOMY 



Malpighian Pyramid 



Cortex 



Cahx 



- - Pelvis 



is prolonged inwards to line a cavity to which the hilum leads, called 

 the sinus, where it becomes continuous with the fibrous coats of 

 the calices. 



When a kidney is cut into two halves by a longitudinal incision 

 carried from the outer to the inner border, it is seen to be composed 

 of two parts — cortical and medullary. 



The medullary part, which is internal in position, is arranged in 

 conical bundles, termed the pyramids of Malpighi, which vary in 

 number from eight to eighteen, the average number being about 

 twelve. The bases of these pyramids are directed towards the cir- 

 cumference, whilst their apical parts, called papillce, project into the 

 sinus, where they are grasped by the calices. Each Malpighian 



pyramid is divided 

 into three parts, 

 namely, the boundary 

 zone or basal part, the 

 papillary zone, and 

 the apex. The bound- 

 ary zones of the pyra- 

 mids form collectively 

 the boundary or inter- 

 mediate layer of the 

 kidney. They abut 

 against the cortical 

 substance, which 

 sends prolongations 

 between them, called 

 septula renum or 

 columncB Bertini. 

 Ureter jhesc prolougatious 

 extend as far as the 

 commencement of the 

 apical parts of the 

 papillary zones, where 

 the}^ cease, so that 

 these apical parts project into the calices free from cortical in- 

 vestments. Each Malpighian pyramid is composed of straight, 

 slightly diverging uriniferous ■ tubules {tubuli recti) and straight 

 bloodvessels, the number of tubules being very much greater 

 in the boundary zone or basal part than elsewhere. This straight 

 arrangement of tubules and bloodvessels imparts to each pyramid 

 a longitudinally striated appearance from apex to base. The 

 boundary zones or basal parts have a dark reddish-brown colour, 

 which becomes brighter in the papillary zones. 



The cortical part of the kidney is mainly situated within the 

 fibrous capsule. It has a reddish-brown colour and, as already 

 stated, sends prolongations between the Malpighian pyramids. 

 Like tlie medullary part, it is composed of uriniferous tubules and 

 bloodvessels, but the tubules are principally convoluted (tubuli 



Fig. 



353. — Diagram of the Kidney in 

 Longitudinal Section. 



