cryptorchidism is the failure of the testes to descend into the scrotum at birth.
failure of the testes to descend into the scrotum at birth?
cryptorchidism
the testes remain high in the abdomen until the seventh month of gestation, when they move from the abdomen through the inguinal canals into the two sides of the scrotum. movement has been proposed to occur in two phases, under the control of somewhat different factors. the first phase, movement across the abdomen to the entrance of the inguinal canal, appears controlled (or at least greatly influenced) by anti-müllerian hormone (amh). the second phase, in which the testes move through the inguinal canal into the scrotum, is dependent on androgens (most importantly testosterone). in rodents, androgens induce the genitofemoral nerve to release calcitonin gene-related peptide, which produces rhythmic contractions of the gubernaculum, a ligament which connects the testis to the scrotum, but a similar mechanism has not been demonstrated in humans. maldevelopment of the gubernaculum, or deficiency or insensitivity to either amh or androgen can, therefore, prevent the testes from descending into the scrotum. some evidence suggests an additional paracrine hormone, referred to as descendin, may be secreted by the testes.
cryptorchidism
having the scrotum and testicles situated outside the abdominal cavity may provide additional advantages. the external scrotum is not affected by abdominal pressure. this may prevent the emptying of the testes before the sperm were matured sufficiently for fertilization. another advantage is it protects the testes from jolts and compressions associated with an active lifestyle. animals that move at a steady pace – such as elephants, whales, and marsupial moles – have internal testes and no scrotum. unlike placental mammals, some male marsupials have a scrotum that is anterior to the penis, although there are several marsupial species without an external scrotum. in humans, the scrotum may provide some friction during intercourse, helping to enhance the activity.
scrotum