Final answer:
The scrotum helps to maintain an optimal temperature for sperm by adjusting its position relative to the body, contracting to absorb heat when it's cold and relaxing to cool down when it's warm, ensuring sperm viability and motility.
Step-by-step explanation:
The features of the male reproductive tract that help keep the sperm at an optimal temperature for viability include the scrotum, which is an external pouch that holds the testes and is located outside the body. This is crucial because sperm production in the seminiferous tubules is very sensitive to temperature.
The optimal temperature for spermatogenesis is about 2 degrees Celsius cooler than the body's core temperature. To maintain this temperature, the scrotum can adjust its position closer to or farther from the body to regulate heat exchange. When it's cold, the smooth muscles lining the scrotum contract, pulling the scrotum closer to the body to absorb body heat. Conversely, when it's warm, the scrotum relaxes, allowing the testes to be farther away from the body to cool down. This temperature regulation is vital for maintaining sperm motility and overall reproductive health.