Morphogenesis of penis and spongy urethra during human gestation.

Background. Every year, approximately 500,000 children in the world are born with congenital abnormalities of the urinary system and kidneys. Therefore, pediatricians and urologists must understand the normal processes that lead to male sexual differentiation. Objective. The aim of this study was to describe in detail the process that occurs during masculinization of the fetus, which leads to the formation of male structures under normal conditions. Methods. Fifty-four fetuses with gestation periods between four and 18 weeks were collected, which were considered normal, did not have any signs of external anatomic abnormalities or any alteration in their development, and were a product of spontaneous abortions and tubal pregnancies. The urogenital sinus region was collected and prepared for scanning electron microscopy and high-resolution optical microscopy to observe the cellular characteristics of the urogenital fold during external development in male embryos. Results. This work shows the formation of the glans and spongy urethra in a detailed manner from the eighth week of embryonic development, carefully describing the role of the labioscrotal folds and the fusion of the walls of the urogenital fold during the subsequent stages of development to form the proximal part of the urinary tract. Conclusion. The formation of the penile urethra from the urethral fold and its posterior fusion have a probable role of ectodermal cells, in addition to the endodermal origin established previously. [ABSTRACT FROM AUTHOR]