What function do the testicles serve in the male body?

The testicles, or testes, play a crucial role in the male reproductive system primarily through the production of sperm and testosterone. Sperm production occurs in the seminiferous tubules within the testicles, where germ cells undergo a complex process of meiosis, ultimately leading to the formation of mature spermatozoa. This process is essential for reproduction, as sperm are required for fertilization of the female egg.

In addition to sperm production, the testes are the main site for the synthesis of testosterone, the primary male sex hormone. Testosterone is vital for the development of male secondary sexual characteristics, such as increased muscle mass, body hair growth, and deeper voice. It also plays an important role in the overall regulation of various bodily functions, including libido and the maintenance of reproductive tissues.

The other options provided do not accurately reflect the functions of the testicles. The production of eggs and estrogen pertains to the female reproductive system. Storage of urine is a function of the bladder, and regulation of blood pressure is primarily managed by the cardiovascular system, not the testes. This highlights the unique and critical role of the testicles in male reproductive health and hormone production.