Development and Morphogenesis of Testis in Human Fetuses

Development and maturation of prenatal testis was studied on 104 human male fetuses. At 9 weeks, the testes were seen as elongated yellowish tissue superolateral to the developing urinary bladder and medial to mesonephros. The testis assumed ellipsoidal shape at 13 weeks. At about 16 weeks, the testes developed convexity on its anterior aspect. Epididymis and testis were at the same level until 20 weeks thereafter the upper testicular pole was encroached upon by the epididymis, with complete encroachment till its anterior aspect at 24 week. The sinus was also distinctly present between the two. The testis assumed miniature adult testis at term, but its size was approximately 1/15th of the adult. Cytoarchitecture of the testis at 9 weeks revealed radially disposed sex cords. At 13 weeks, tunica albuginea,tubular organization in the parenchyma and the Leydig cells were identifiable. At 17 weeks, tunica vasculosa and incomplete lobules were apparent. At 24 weeks, testis was marked by more but solid seminiferous tubules lined by 4-5 germ layers. Leydig cells were also identifiable till 24 weeks. Spermatogenic cells, both pale and dark type were distinguishable although pale spermatogonia were more numerous than dark cells. 28 weeks onwards tunica vaginalis and complete septa in the testicular parenchyma were evident. Moreover, the seminiferous tubules developed central vacuolation. By 30 weeks, seminiferous tubules became more complex as evident by their increase in number and coiled and tortuousity. At term, the fetal testis had not yet attained the cytoarchitecture of the adult testis suggesting that testicular maturation continues postnatally.