Testes: descent of the testes
Testes develop in the abdomen. The precursor to the testis is the gonadal ridge. The testes develop from mesothelium in the gonadal ridge and underlying mesonephros.
The testes develop at the superior end of a structure called the gubernaculum. The gubernaculum is a cord like structure (also called the caudal genital ligament) that is anchored to the scrotum inferiorly and pulls the testes down into the scrotum during fetal development.
The course of the gubernaculum is through what will become the inguinal canal into the scrotum. The first phase of scrotal migration is across the abdomen (trans-abdominal) and is typically the result of the abdominal cavity enlarging but the testis being anchored by the gubernaculum. The second part is the transinguinal phase where the testis moves through the inguinal canal into the scrotum.
In the transinguinal phase a finger like fold of peritoneum called the processus vaginalis descends along the course of the gubernaculum, starting at the deep inguinal ring, and takes with it the muscle layers of the abdominal wall that will eventually form the fascial layers of the testes. As the testis descends it pulls with it the vas deferens, blood vessels and lymphatics of the spermatic cord.
The processus vaginalis pinches off to become the tunical vaginalis layer covering the testes. The upper part of the gubernaculum degenerates whilst the lower part of the gubernaculum persists as the gubernaculum testis or scrotal ligament. The scrotal ligament anchors the testis to the scrotum limiting movement of the testes.
In females the ovaries descend in a similar way but their descent stops in the pelvis and the inguinal canal contains only the remnants of the gubernaculum.
The video below illustrates the descent of the testes.
The testes develop at the superior end of a structure called the gubernaculum. The gubernaculum is a cord like structure (also called the caudal genital ligament) that is anchored to the scrotum inferiorly and pulls the testes down into the scrotum during fetal development.
The course of the gubernaculum is through what will become the inguinal canal into the scrotum. The first phase of scrotal migration is across the abdomen (trans-abdominal) and is typically the result of the abdominal cavity enlarging but the testis being anchored by the gubernaculum. The second part is the transinguinal phase where the testis moves through the inguinal canal into the scrotum.
In the transinguinal phase a finger like fold of peritoneum called the processus vaginalis descends along the course of the gubernaculum, starting at the deep inguinal ring, and takes with it the muscle layers of the abdominal wall that will eventually form the fascial layers of the testes. As the testis descends it pulls with it the vas deferens, blood vessels and lymphatics of the spermatic cord.
The processus vaginalis pinches off to become the tunical vaginalis layer covering the testes. The upper part of the gubernaculum degenerates whilst the lower part of the gubernaculum persists as the gubernaculum testis or scrotal ligament. The scrotal ligament anchors the testis to the scrotum limiting movement of the testes.
In females the ovaries descend in a similar way but their descent stops in the pelvis and the inguinal canal contains only the remnants of the gubernaculum.
The video below illustrates the descent of the testes.