Testicular development and descent

Last revised by Henry Knipe on 24 Feb 2024

Testicular development and descent is an important topic due to the clinical gonadal manifestations seen in children and adults secondary to abnormal development.

The testes are derived from the gonadal ridge medial to the mesonephric ridge of the intermediate cell mass. 

By the 8th week of development, the testis is attached at its caudal pole to the gubernaculum, a mesenchymal linear band, to the lower abdominal wall in the inguinal region (between the internal and external oblique muscles).

As the intra-abdominal phase of descent starts, the gubernaculum grows inferiorly towards the scrotal swellings, pulling the testis down with it. At the same time, and completely independently, an elongated diverticulum of peritoneum from the anterior lower abdominal cavity develops, the processus vaginalis. This invaginates through the abdominal wall and together with the gubernaculum-driven testicular descent, forms the spermatic cord along with the inguinal canal, deep and superficial inguinal rings.

The testis envaginates into the peritoneal covering forming a pouch. The cranial part of the processus vaginalis then obliterates and the caudal part that envelops the testis and the tunica albuginea becomes the tunica vaginalis

The timing of descent is as follows:

  • 4th fetal month - near the deep inguinal ring

  • 7th 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). 

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