234 



UROGENITAL SYSTEM 



drical fold of the epithelium, incomplete on the anal side, grows down into the 

 end of the glans, which becomes the glans penis. By the disappearance of the 

 central cells of the epithelial downgrowth an outer cylindrical mantle, the pre- 

 puciiim or fore-skin, is formed about the spherical glans. Where the epithelial 

 downgrowth is incomplete the glans and foreskin remain connected, the persist- 

 ing connection being the frenulum 

 prcpucii. 



The urogenital sinus, as we have 

 seen, extends out into the phallus 

 and in the glans becomes the solid 

 urethral plate. With the great 

 elongation of the male phallus, the 

 open portion of the urogenital sinus 

 also is lengthened and forms the 

 greater part of the penile urethra. 

 In embryos of 70 mm. the groove- 

 like primitive urogenital opening, 

 located in the male near the glans 

 and distant from the anus, closes 

 and thus is formed a further por- 

 tion of the urethra. The failure of 

 this opening to close gives rise to 

 an anomaly known as hypospadias. 

 The lips of the urogenital opening, 

 it will be remembered, correspond 

 to the labia minora or nympkee of 

 the female. Finally at 100 mm. 

 the solid urethral plate of the 

 glans splits, forms a groove to the 

 tip of the glans and this groove in turn is closed, continuing the urethra to the 

 definitive opening at the tip of the glans. Owing to the rapid growth in 

 length of the penis, there is formed between its base and the anus an 

 unpaired area, termed by Felix the scrotal area as it is the anlage of the 

 scrotum. At 60 mm. this forms a median scrotal swelling continuous with 

 the paired genital swellings. When the scrotal sac develops in the scrotal area, 

 the dense tissue in the median line is compressed and forms the septum scroti. 

 The attachment of this septum forms an external median depression. The testes 



FlG. 230. — Four stages in the development of the 

 male external genitals (Tourneux in Heisler). r, 

 penis; 2, glans; 3, urogenital groove; 4, urogenital 

 swellings corresponding to labia majora of female; 

 5, amis; 6, coccygeal eminence; 7, scrotal area with 

 perineo-scrotal raphe. 



