CHAPTER VIII 

 UROGENITAL SYSTEM 



The urogenital system is composed of distinct urinary and genital glands 

 which, however, possess common ducts and have a common origin from the meso- 

 derm. \The excretory glands are the pronephros, mesonephros, and metanephros, 

 organs which develop in this order. The first two named are the temporary kid- 

 neys of the mammalian embryo, but are functional in adult fishes and amphibia. 

 The metanephros is the permanent kidney of reptiles, birds and mammals./ 



THE PRONEPHROS 



i The pronephros, when functional, consists of paired segmentally arranged 

 tubules, one end of each tubule opening into the ccelom, the other into a longitu- 



Antaquof 

 pranephrit duct 



En to derm 



.-Splanchnic 

 mesoderm 



\ Notochoi-d 



FIG. 197. Diagrams showing the development of the pronephric duct and pronephric tubules (modi- 

 fied from Felix). A shows a later stage than B. 



dinal pronephric duct which drains into the cloaca (Fig. 197 A). /Near the 

 nephrostome, the opening into the ccelom, knots of arteries project into the tubules, 



203 



