THE ENDOCRINE SYSTEM 



629 



Both ovaries and testes develop from mesoderm, from the genital 

 ridge on the ventral side of the mesonephros (Fig. 30.11). It consists of 

 closely packed cells covered by a thickened mesothelium called the 

 germinal epithelium. During embryonic development certain cells of 

 the germinal epithelium enlarge, push into the mass of cells below, 

 and become primordial germ cells. According to one view, these cells 

 are not derived from the mesothelium, but originate in the epithelium 



MesONEPHROS 



.GENITAL RIDGE 



RETE PORTION 



WOLFFIAN 

 DUC 



CLOACA 



GERMINAL EPITHELIUM 



■SEX CORD 

 PORTION 



PRIMARY .^ , 



SEX CORDS — j^^\ 



RETE CORDS — (^ — - 



POSrSEXUAL PORTION 



GENITAL RIDGE 

 MESONEPHROS, 



MULLERIAN DUCT 

 WOLFFIAN DUCT 



CLOACA 



■APPENDIX TESTIS 



TESTIS ^ 

 (PRIMARY SEX^ 

 CORDS) 



GERMINAL EPITHELIUM 

 TUNICA ALBUGINEA 

 RETE TESTIS 



TUNICA ALBUGINEA 



Oi^ARlAN 

 MEDULLA 



(primary sex 



CORDS) 



^ OVARIAN CORTEX 

 (SECONDARY SEX CORDS) 



GERMINAL EPITHELIUM 



SEMINAL 

 VESICLE 



URINARY BLADDER 



PROSTATIC UTRICLE 

 PROSTATE GLAND 



GARTNER'S 

 DUCT 



PAROOPHORON 



'RETHRA 



Figure 30.11. The development of the genital system. A, Section through the 

 dorsal region of an early embryo. B, The Wolffian body and genital ridge in frontal 

 section. C, The indifferent stage. D, Differentiation of the male genitalia. E, Differen 

 tiation of the female genitalia. (Modified from Turner.) 



