MALE BODY CLOCK
Puberty begins for boys between ages 10 and 14, and most often around ages 11 or 12. The onset of puberty is triggered by the male sex hormones testosterone and androgen. The sequence of physical changes is usually as follows:
1. Growth of testes (testicles) and scrotum. This is accompanied by reddening and wrinkling of scrotal skin. Testes are male reproductive glands that produce sperm and male hormones. Once they begin sperm production, it generally continues throughout a man's life unless he is hurt or ill.
2. Appearance of pubic hair. Long strands of straight pubic hair appear at the base of the penis, then spread over the scrotum and up the abdomen. Pubic hair is straight until after the first ejaculation - then it becomes curlier.
3. Growth spurt. Arms, legs and penis grow rapidly. A boy typically grows 3 to 5 inches taller within a year's time. The trunk grows approximately 1 year after the arms and legs so limbs appear lanky and awkward. The voice begins to deepen as a result of internal growth of the larynx. Boys who experience their growth spurt later than others may need reassurance that their bodies will develop.
4. First ejaculation. This occurs about 1 year after growth of testes and scrotum. Indicates that a boy is producing sperm and is capable of reproduction.
5. Underarm and coarser body hair appear. This generally occurs 2 years after pubic hair appears.
6. Facial hair (beard) develops and voice deepens. These badges of manhood are usually the last change to appear.
This order may vary, but not by much. It is the same for almost all boys. The different steps or stages of development may not be as distinct or easily recognized as this list would indicate - some changes may be so slight that they are unnoticed.
Adapted from In Between: A Family Life Education Curriculum