The onset of puberty may vary from 11 to 15 years of age for boys. This is a time of significant changes as he goes from childhood into adulthood. The effects of testosterone in these years include changes in body hair, deepening of the voice and rapid muscle growth. There is also an increase in sexual awareness. Hormone changes in body secretions, along with skin bacteria, can lead to a change in body odor.
Sperm production begins and there is rapid growth of the penis and testes.
There is a separate compartment for the right and left testicle. A wall separates the two testicles. The scrotum also has muscles in the walls, which hold the testes close to the body when the individual is cold, and allows the testes to swing away from the body when conditions are warm. Maintaining constant testis temperature is critical for sperm production. It is this cord that gets twisted by testis torsion, sometimes interrupting blood flow to the testis.