Editing Undescended Testicle (section)

== Normal testicular descent ==

* '''Factors contributing to descent (5):'''
*# '''Testis'''
*# '''Genitofemoral nerve'''
*# '''Hormones'''
*# '''Gubernaculum'''
*# '''Processus vaginalis'''
** '''Genitofemoral nerve'''
*** Origin: L1, L2
*** Motor: genital branch innervates cremesteric muscle
*** Sensory: genital branch provides sensation from anterior scrotum; femoral branch provides sensation from upper anterior thigh
** '''Hormones'''
*** '''Descent is regulated by 2 Leydig cell hormones:'''
***# '''Insulin-like 3 (INSL3)''' via its receptor relaxin/insulin-like family peptide receptor 2 (RXFP2)
***# '''Androgens (testosterone)''' via the androgen receptor (AR)
**** Downstream pathways are poorly defined
**** '''These hormones peak at 14-17 weeks and stimulate development of the gubernaculum and testicular descent in the second and third trimesters'''
**** '''Altered expression or function of key molecules that participate in testicular and/or gubernacular development could potentially contribute to an increased risk of cryptorchidism'''
** '''Gubernaculum'''
*** '''Caudal gonadal ligament that faciltates gonadal descent in both sexes'''
**** No cranial gonadal ligament exists in humans as noted in other species
*** '''Develops in both sexes beginning at 7 weeks’ gestation'''
*** '''Swelling of the gubernaculum, which starts in the second trimester, provides space for passage of the testis'''
* '''<span style="color:#ff0000">The testis passes into the inguinal canal at 20 to 28 weeks’ gestation'''
** '''<span style="color:#ff0000">Majority of testes are scrotal by 27 weeks'''
** '''Time spent in the inguinal canal seems to be limited for the majority of human fetal testes'''