Morfogénesis del sistema reproductor del perro

Abstract

The objective of this report was to characterize the sequence of embryonic genital system in dogs to establish the stages of development and differentiation of the gonads. Many embryos at different developmental stages were isolated from twenty uteri. They were dissected, topographically and morphologically analyzed with a stereoscopic microscope in order to determine the gonadal differentiation stage. Tissue sections were taken from ovaries and testes, stained with hematoxylin and eosin and gonad organization was determined by light microscopy. Undifferentiated genital crests in stages 5 to 7 were observed medial to the mesonephros as elongated masses. The morphological differentiation between males and females was observed in stage 8. From stage 9 changes in gonads' position were noted due to metanephros emergence and mesonephros regression. The external genitalia were undifferentiated until stage 14. The histological organization showed that the ovaries had a thick cortex with nests of eggs and a medulla of connective tissue. In the testes a thin cortex and medullar testicular cords in formation were seen. In stage 6 Müller and Wolff ducts appeared in both sexes. In males the müllerian duct's regression was observed in stage 10 and its disappearance on stage 14. In females the Wolff duct showed regression in stage 14. In general, canine specie follows a similar morphological development line as seen in other mammals. Histological organization of the gonads showed earlier testicular differentiation compared to ovary differentiation.