The gonads are the primary reproductive organs of both male and female. The Y chromosome determines differentiation of the gonads. If the Y chromosome is present, testicular development will occur about six weeks after fertilization. However, if the Y chromosome is not present, the embryonic cells in the gonadal region will develop into the ovaries. The gonads produce the sex cells, called gametes, and secrete gonadotropic hormones. The gonadotropic hormones stimulate gametogenesis, the transformation of immature sex cells into mature gametes. Once gametes mature, the male gametes, or sperm, are capable of fertilizing a female egg called an ovum.

The testes, or male gonads, are paired structures that produce sperm. The testes, also known as the testicles, are oval structures that are about 1.6-1.96 in. (4-5 cm) in length and 0.98 in. (2.5 cm) in diameter. The scrotum is a pouch of...