Final answer:
The scrotum and testes maintain a temperature around 2 to 4°C lower than body temperature to support sperm production, employing muscle contractions for temperature regulation. Viable sperm are produced under these conditions, with immobility at higher temperatures leading to infertility risks.
Step-by-step explanation:
The scrotum and testes maintain a lower temperature than the core body temperature to facilitate the production of viable sperm. Sperm production, or spermatogenesis, is optimal at temperatures around 2 to 4°C below the body's core temperature. The scrotum, a skin-covered muscular sack containing the testes, adjusts its temperature through the contraction and relaxation of the cremaster and dartos muscles, which respectively elevate the testes toward the body to warm them or allow them to hang further away to cool down.
This precise temperature regulation is crucial because sperm are immobile at body temperature and infertility may occur if the testes fail to descend into the scrotum during fetal development. As land mammals, humans' reproductive success depends on maintaining this cooler environment for the testes, which is external to the body's main cavity.