Development and descent of the testis

Abstract

Normal testicular descent is achieved by a residuum of primitive embryonic mesenchyme which is retained through into the fetal period; this is the gubernaculum testis. It forms a medium into which the cremaster muscles and the processus vaginalis can develop in anticipation of testicular descent. At the time of descent the gubernacular mesenchyme dilates, largely due to the uptake of fluid by the interstitial hyaluronic acid. By this means the scrotal sac is dilated and, with concurrent growth of related structures, all under the overall influence of maternal and chorionic gonadotrophic (luteinising) hormones, stimulating the testicular interstitial cells of the fetal testis, testicular descent is permitted.

Failure to maintain the undifferentiated gubernacular mesenchyme, as by invasion of differentiating tissues, mechanically prevents the necessary growth to normal descent and may thus produce ectopic testes. Failure of the fetus to respond to luteinising hormones either by testicular interstitial cellular response, or the other tissues' response to normally produced testosterone, leads to an essentially hormonal failure of descent (cryptorchidism). Commonly, the failure to descend is no more than a premature birth, so separating the fetus from its source of luteinising hormone before the descent process is complete. The replacement of that antenatal stimulus of luteinising hormone at an early postnatal stage appears the logical treatment of cryptorchidism. However, if a proper scrotal formation has not occurred, then the indication is that the gubernaculum has not carried out its initial dilating function and probably the testis is deficient in its interstitial cell secreting potential.