Descent of the Testis
The testis develops on the posterior abdominal wall at the mesonephric ridge. To reach the adult position in the scrotum, it must decent. A fibrous cord form and runs from the lower pole of the testis down the posterior abdominal wall and on to the underside of the anterior abdominal wall. The latter part forms the inguinal fold. The terminal part of the fibrous cord (the gubernaculum) negotiates the layers of the anterior abdominal wall and passes into the scrotum where it ends. The function of the gubernaculum is believed to be that of anchoring the testis during the process of straightening. As it descends into the scrotum at approximately the 8th month of fetal life, it draws with it a tube of peritioneum, the processus vaginalis. The lower part of the processus vaginalis remains patent and becomes the tunicia vaginalis testis. The upper part becomes a fibrous cord. If the processus remains patent throughout its length, a congenital indirect inguinal hernia will result. If isolated stretches of the upper part persist, a hydrocele results.
Both testes should be in the scrotum at birth. If the descent of the testis becomes arrested in the abdomen or inguinal canal, undescended testis (cryptorchism) results. The interstitial cells of Leydig will function normally in this position; therefore the secondary male sex characteristics will appear at puberty, but the individual will be sterile because normal spermatogenesis cannot take place in the abdominal body temperature, as if can in its normal position in the cooler scrotum.