What is the primary function of the testes in the male reproductive system?

The primary function of the testes in the male reproductive system is to produce sperm and testosterone. The testes are responsible for spermatogenesis, which is the process of generating sperm cells. This occurs in the seminiferous tubules, where germ cells undergo division and maturation.

In addition to sperm production, the testes also play a critical role in endocrine function through the production of testosterone, which is essential for the development of male secondary sexual characteristics, male reproductive behavior, and overall male health. Testosterone influences traits such as muscle mass, body hair, and voice depth, as well as maintaining libido and sperm production throughout a male's life.

The other options highlight important aspects of the male reproductive system but do not encompass the primary functions attributed to the testes directly. Storing and maturing sperm occur in the epididymis, carrying sperm from the testes is the role of the vas deferens, and the protective and cooling function pertains to the scrotum, which helps maintain an optimal temperature for sperm production and preservation.