DEVELOPMENT OF URINARY AND GENERATIVE ORGANS 1429 



groove, the genital groove, appears, and into its lips the mesoderm extends to form the inner 

 genital folds . After the rupture of the cloacal membrane this groove becomes continuous with 

 the urogenital sinus. With the formation of these parts the indifferent stage of the external 

 genital organs is reached. 



In the female this stage is largely retained; the lower part of the urogenital sinus persists as 

 the vestibule, the genital tubercle forms the clitoris, the labioscrotal folds the labia majora, and 

 the inner genital folds the labia minora. 



Umbilical cord. 

 Genital tubercle. 



Tail. 



Genital tubercle. 

 Labioscrotal fold. 

 Inner genital fold. 

 Genital groove. 



lans penis. 



Labioscrotal fold. 

 Inner genital fold. 

 Genital aroove. 

 Perineum. 



Anus. 



Glans clitoridis. 

 Labioscrotal jold. 

 Inner genital fold. 

 Genital groove. 



Perineum. 

 Anus. 



E 



Glans penis. 

 Genital groove 



Scrotum. 

 Raphe. 



ail- Anus. 



Prepuce. 

 Glans clitoridis. 



Labium ma jus. 

 Labium minus. 

 Vestibule. 

 Vaginal orifice. 



Anus. 



--T man . 



FIG 1189 Stages in the development of the external sexual organs in the male and female. (Drawn from 



the Ecker-Ziegler models.) 



In the male the changes are greater on account of the development of the penile portion of the 

 urethra. The genital tubercle enlarges to form the corpora cavernosa and glans penis, 

 lips of the inner genital folds meet and fuse from behind forward to form the penile urethra, 

 the bulb and the corpus spongiosum. The part of the urethral groove on the glans penis is 

 closed independently, and the last part of the urethral tube to be completed is that at the junction 

 of the glans and body of the penis. If the lips of the groove fail to close, the condition known as 

 hiipospadias results. . .. . 



The labioscrotal folds meet and unite in the middle line to form the scrotum, tl 

 union being indicated by the median raphe. 



