The male and female reproductive organs have evolved over millions of years to propagate the species. Both male and female organs arose from common embryonic origins. In the presence of active male-determining genes on the Y-chromosome, the developmental program for the male reproductive system is activated. In the absence of a Y-chromosome or if male-determining genes are not functional, the female reproductive system develops.
Testicles and Ovaries
Male and female have comparable organs to produce the reproductive cells and hormones they need for reproduction. In men, the externally located testicles produce the predominant male hormone testosterone and produce sperm cells. Women have internal gonads called ovaries, which produce the female hormones, estrogen and progesterone and the female gametes, eggs. In their review, "Onset of Sex Differentiation: Dialog Between Genes and Cells", published in the Archives of Medical Research, Doctors H. Merchant -Larios and N Moreno-Mendoza describe the discovery of the SRY gene on the Y-chromosome and it's role in producing the male gonad. The primordial gonad in the early embryo develops into an ovary unless the embryo inherited a Y-chromosome and active SRY-genes, unleashing a cascade of gene activation and cell signaling that directs the formation of a testicle. Male hormone produced by this organ further pushes the development of both internal and external male genitalia. In the absence of the Y-chromosome with functional SRY-genes, the ovary develops.
Mullerian Duct
The early embryo has parallel duct structures called Mullerian and Wolffian ducts that give rise to either male or female internal transport ducts or genitalia, depending on the genetic and hormonal sex of the embryo, according to the John Hopkins Children's Center website information on "Normal Sex Differentiation". In the female, the Mullerian ducts give rise to the fallopian tubes, uterus and the upper part of the vagina. The fallopian tubes connect the ovary to the uterus where the embryo will implant. Fertilization of the egg and the early days of embryo development occur in the fallopian tube until the embryo has become ready to implant in the uterus. The vagina provides an opening to the female reproductive tract for sperm to enter and find their way to the egg. The uterus provides a place for the developing embryo to implant and produce a placenta, which promotes the nourishment of the developing fetus for the next nine months until birth.
Wolffian Duct
In the male, the Mullerian duct withers away and the Wolffian ducts flourish, according to Dr. P.C. Sizenko, in his article, "Human Sexual Differentiation", published by the Geneva Foundation for Medical Education and Research. The Wolffian ducts give rise to the vas deferens, epididymis and seminal vesicles. The vas deferens is comparable to the fallopian tubes because the vas deferens connects the testicles to the ejaculatory duct in the penis, so that sperm produced in the testis can become transported out of the male body during sexual intercourse. The seminal vesicles produce fluids that make up the fluid part of the semen. The epididymis is a small storage organ located on top of the testicles in which newly formed sperm travel and undergo final processing to make them fully capable of fertilizing an egg when they are ejaculated.
External Gentalia
The external genitalia develop from structures arising from the a embryonic structure called the urogenital sinus and parts of either the Mullerian or Wolffian ducts according to Dr. P.C. Sizenko, in his article, "Human Sexual Differentiation", published by the Geneva Foundation for Medical Education and Research. The lower part of the vagina, cervix and clitoris arises from the lower part of the Mullerian tube and the upper part of the urogenital sinus. The cervix is a small organ, which joins the uterus to the vagina, acting as a gateway to the uterus and producing thick protective mucous during non-fertile periods.The clitoris is a small structure which provides pleasurable sensations during intercourse.
In the male, the urogenital sinus grows and enlarges into the duct structures that will ultimately form the ejaculatory ducts, the prostate, the scrotum and penis. The prostate grows around the ejaculatory duct and produces another kind of fluid, which proves an essential component in the semen. The penis is the sexual organ that enters the vagina and aids sperm transport between the sexes. The scrotum is a protective sac that holds the testicles, epididymis and vas deferens outside the body, keeping the testicles at a slightly cooler temperature for optimal function.
