Final answer:
Cryptorchid testes are underdeveloped and fibrotic primarily due to excessive heat exposure since undescended testes remain at the higher internal body temperature, leading to testicular dysfunction and impaired fertility.
Step-by-step explanation:
Cryptorchid testes are hypoplastic and fibrotic due to excessive heat exposure. Normal testicular descent into the scrotum is essential for providing a cooler environment for the testes, which is crucial for proper spermatogenesis and testicular development.
When testes remain undescended, as seen in cryptorchidism, they are subjected to the higher internal body temperatures, which leads to their underdevelopment (hypoplasia) and the buildup of fibrous tissue (fibrosis).
This condition can impair fertility and increase the risk of testicular cancer if not corrected in a timely manner. The scrotal location of the testes in many mammals, including humans, allows for temperature regulation that is essential for normal testicular function and spermatogenesis.
It is known from various studies and sources, including LibreTexts, that activities such as soaking in hot tubs and wearing tight clothing that increase the heat of the scrotal area can negatively impact fertility, although short-term heat exposure is typically temporary in its effects. However, cryptorchid testes are continuously exposed to high temperatures, which can cause long-term damage.