A 6 month old child is brought to the surgical clinic because of non descended testes. What is the main structure that determines the descent path of the testicle?
The gubernaculum is a ridge of mesenchymal tissue that connects the testis to the inferior aspect of the scrotum. Early in embryonic development the gubernaculum is long and the testis are located on the posterior abdominal wall. During foetal growth the body grows relative to the gubernaculum, with resultant descent of the testis.
Until the end of foetal life the testicles are located within the abdominal cavity. They are initially located on the posterior abdominal wall on a level with the upper lumbar vertebrae (L2). Attached to the inferior aspect of the testis is the gubernaculum testis which extends caudally to the inguinal region, through the canal and down to the superficial skin. Both the testis and the gubernaculum are extra-peritoneal.
As the foetus grows the gubernaculum becomes progressively shorter. It carries the peritoneum of the anterior abdominal wall (the processus vaginalis). As the processus vaginalis descends the testis is guided by the gubernaculum down the posterior abdominal wall and the back of the processus vaginalis into the scrotum.
By the third month of foetal life the testes are located in the iliac fossae, by the seventh they lie at the level of the deep inguinal ring.
The processus vaginalis usually closes after birth, but may persist and be the site of indirect hernias. Part closure may result in development of cysts on the cord.