Cryptorchidism (over 90% in some studies). Even after orchiopexy, these may also affect sperm maturation and motility at an older age. The most common diagnostic dilemma in otherwise normal boys is distinguishing a retractile testis from a testis that will not descend spontaneously into the scrotum. Retractile testes are more common than truly undescended testes and do not need to be operated on. In normal males, as the cremaster muscle relaxes or contracts, the testis moves lower or higher ("retracts") in the scrotum. This cremasteric reflex is much more active in infant boys than older men. A retractile testis high in
Scrotum groove closes by week 12. Though the testes and scrotum form early in embryonic life, sexual maturation begins upon entering puberty. The increased secretion of testosterone causes the darkening of the skin and development of pubic hair on the scrotum. The scrotum regulates the temperature of the testes and maintains it at 35 degrees Celsius (95 degrees Fahrenheit), i.e. two degrees below the body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit). Higher temperatures affect spermatogenesis Temperature control is accomplished by the smooth muscles of the scrotum moving the testicles either closer to or further away from the abdomen dependent