What is the function of the Cowper's glands?

The Cowper's glands, also known as bulbourethral glands, play a crucial role in male reproductive health by secreting a clear, viscous fluid that helps to lubricate the urethra. This pre-ejaculatory fluid assists in neutralizing any acidity in the urethra and provides a smoother passage for sperm during sexual activity. This lubrication is critical as it facilitates ejaculation and minimizes discomfort by ensuring that the urethra is well-prepared for the passage of semen.

The other options pertain to different functions that are not associated with the Cowper's glands. For instance, while testosterone is essential for male reproductive functions, it is produced primarily by the testes. Similarly, the regulation of sperm production and control of ejaculation are functions associated with the testes and the nervous system, respectively, not the Cowper's glands. Therefore, the secretion of a lubricating fluid for the urethra is the primary and defining role of the Cowper's glands.