Testicular descent

Testicular descent occurs after the fourth month of fetal life. The testes are derived from the gonadal ridge medial to the mesonephric ridge of the intermediate cell mass. An elongated diverticulum of the peritoneal cavity, the processus vaginalis precedes the testis through the inguinal canal into the scrotum, and the testis moves down behind this. The processus becomes obliterated except at its lower end where the testis invaginates into it from behind to become the tunica vaginalis.

The timing of descent is as follows:

• 4 fetal month - near the deep inguinal ring
• 7 fetal month - within the deep inguinal ring
• in the next few days to weeks, it descends into the scrotum

Failure of the testes to descend may result in cryptorchidism. Failure of the obliteration of the whole processus vaginalis leads to the formation of an indirect inguinal hernia. Persistence of part of the processus leads to the formation of a hydrocele (of the cord or testis).