Normal Testicular Descent

The normal process of testicular descent is complex and multi-staged rather than being a simple, one-stage mechanism. Descent of the testis occurs only in mammals. A review of different species shows evolution of the position of the gonad from the urogenital ridge in the abdominal cavity first at the groin and then outside the abdominal wall and into a definitive scrotum (Williams and Hutson 1991b). Migration to an extra-abdominal site has enabled the testis to function at a temperature below that of the rest of the body, with the scrotal testis of the human adapted to 33°C (Zorgniotti 1991).