THE UROGENITAL SYSTEM 



437 



sinus. The septum, which is completed during the seventh week, becomes 

 the perineum of the adult. After the septum is formed the mesonephric 

 ducts and ureters retain their connexion with the urogenital sinus. Even 



NEPHROGENIC TISSUE 



Fig. 363. — A diagram illustrating the repeated branching of the collecting tubules 

 in a nine weeks (30 mm.) human embryo. The diagram also shows the origin of 

 secretory tubules from the nephrogenic tissue. (Redrawn from Braus, after 

 Kampmeier.) 



before the development of the septum is completed, in an 11 mm. embryo, 

 the urogenital sinus becomes subdivided into a vesico-urethral portion 

 into which the ureter and mesonephric ducts enter, and a phallic portion 



CONNECTIVE TISSUE CAPSULE 

 NEPHROGENIC TISSUE 



-COLLECTING TUBULE 



GLOMERULUS 

 BLOOD VESSEL 



Fig. 364. Section of the kidney of a 38 mm. human embryo. The section shows the 

 branching of the collecting tubules and the relation of their terminations to the nephro- 

 genic tissue from which the secretory tubules are derived. (Redrawn after Coming's 

 "Htunan Embryology.") 



which extends into the genital tubercle. By the time the embryo attains 

 a length of 25 mm. (2 months), the ureters and mesonephric ducts are 

 separated, the ureters open into the bladder, and the mesonephric ducts 

 into the urethra. The bladder, therefore, arises not from the allantois 



