Primary sex organs are those organs of reproductive system, which directly participate in the process of reproduction. In humans males, the primary sex organs are testes, and in females, the primary sex organs are ovaries. Apart from producing sperms and ovum, these organs also release some reproductive hormones, namely, testosterone (from testis) and oestrogen and progesterone (from ovaries), which control the growth, function and maintenance of other reproductive system organs, like epididymis, vas deferens (in males) fallopian tube and uterus (in females), also called the secondary sex organs. Hence primary sex organs control the growth, function and maintenance of secondary sex organs.