Sexual Organogenesis

Abstract

The foundations that underlie our knowledge of sexual differentiation were built long ago. Some remain strong and secure, especially those concerning the sex ducts, the external genitalia, and the relations between the mesonephros and sex structures. Other long-accepted views have failed to be properly verified and dim our understanding of the real events; this assertion applies especially to the prob- lem of gonadal differentiation. Before entering into particulars, it probably is appropriate to recall some of the anatomical and embryological bases of the structures involved (Figure 1). Some sex structures are homologous in the male and female in that the same primordium differentiates into structures characteristic of either sex; such is the case for the derivatives of the urogenital sinus and of the genital tubercle. Other parts are not strictly homologous in both sexes as they derive from different primordia. Thus, the fetal Wolffian ducts (the excretory ducts of the transitory mesonephric kidney) produce the vasa deferentia, the epididymides, and the seminal vesicles in males; the fetal Mullerian ducts become the tubes and the uterus in females. It should be understood that the terms Wolffian and Mullerian ducts refer essentially to the inner epithelial lining of these ducts and that the mesenchyme that forms the connective chorion and the muscularis is common to both sexes