Final answer:
The testes are located outside the body in the scrotum to maintain a temperature approximately 2°C lower than core body temperature, which is vital for efficient sperm production and to prevent infertility.
Step-by-step explanation:
The testes need to maintain a temperature that is slightly cooler than the rest of the body for efficient sperm production and viability. Sperm production, or spermatogenesis, occurs at an optimal temperature, which is about 2 degrees Celsius lower than the body's core temperature. The scrotum, which houses the testes, facilitates this temperature regulation through the contraction and relaxation of its muscle layers, particularly the dartos and cremaster muscles.
The temperature of the scrotum and testes fluctuates with environmental conditions. When it is cold, the scrotal muscles contract to bring the testes closer to the body for warmth, and during warmer conditions, the muscles relax, moving the testes away from the body to avoid overheating. This precise temperature control is crucial because sperm are immobile at higher temperatures, and prolonged exposure to core body temperature can lead to infertility.