(a) The changes observed in boys during puberty are:

Hair grows under armpits, pubic region between the thighs, chest and face. Body becomes more muscular due to the development of muscles. The voice deepens. Chest and shoulder broaden. The penis and testes become larger. Feelings and sexual drives associated with adulthood begin to develop.

(b) Testes.

(c) Working of human male reproductive system: The human male reproductive system consists of:

(i) Testes: Are the primary reproductive organs in males which are in pair. These are oval shaped organs which lie outside the abdominal cavity. It makes the male sex cells called sperms and produces male sex hormones called testosterone.

(ii) Scrotum: Is a muscular pouch which houses the testes. It is present outside the abdominal cavity and maintains a lower temperature than the normal body temperature.

(iii) Epididymis: The sperms formed in the testes goes into a coiled tube called epididymis which stores the sperms temporarily.

(iv) Vas Deferens (sperm duct): It is a long tube which carries the sperms from epididymis to another tube called urethra.

(v) Seminal vesicles and prostrate gland: Both these glands are present along the path of vas deferens and add their secretions to sperms which allows them to transport easily.

(vi) Penis: It is an organ which passes the sperms from the man’s body into the vagina in the women’s body during mating.

(d) The secretions of seminal vesicles and prostrate gland provide nutrition to the sperms and also make their transportation easier by secreting a thick liquid.

The male reproductive system in humans (side view).