Seminiferous Tubules

The seminiferous tubules provide a unique environment for the production of germ cells. The structures involved in this process include germinal elements and supporting cells. The supporting cells include the peritubular cells of the basement membrane and the Sertoli cells. The germinal elements comprise a population of epithelial cells, including a slowly dividing primitive stem cell population, the rapidly proliferating spermatogonia, spermatocytes undergoing meiosis, and the metamorphosing spermatids. The seminiferous tubule also produces an environment known as "the blood-testis barrier". The testis is unique in that the differentiating germ cells are potentially antigenic, and recognizable as foreign; however, little immunological reaction is usually detectable within the testis.

Developmentally, the testis develops from the undifferentiated gonad. These primitive germ cells are referred to as gonocytes after the gonad differentiates into a testis by forming seminiferous cords. At this time, the gonocytes are located in a central position within the seminiferous cords. They are subsequently classified as spermatogonia after the gonocytes have migrated to the periphery of the tubule. From birth to approximately 7 years of life, there appears to be very little morphological change within the human testis. From 7 to 9 years of life, mitotic activity of gonocytes is detectable, with spermatogonia populating the base of the seminiferous tubule in numbers equal to those of the Sertoli cells. There appears to be little further morphological change in spermatogonia until spermatogenesis begins at the time of puberty. Further information regarding the maturation of gonocytes and their migration to the base of the seminiferous tubule, including the factors that may be responsible for these changes, may provide greater insight into the effects of cryptorchidism on fertility and impact on the appropriate timing of intervention for treatment of cryptorchidism.