The reproductive organs of humans, while ostensibly quite different from males to females, actually share most of their developmental roots. Early fetuses have identical reproductive systems, despite the fact that a baby's gender is determined from the moment of its conception. Under the influence of male hormones, fetal reproductive organs develop into those associated with the human male, while the absence of these hormones produces female reproductive anatomy. Despite similarities in developmental origin, the reproductive organs of men and women are different in both form and function.
Gonads
The gonads, explains Dr. Lauralee Sherwood in her textbook "Human Physiology," are the organs responsible for producing male or female hormones and sex cells in men and women respectively. Male gonads, called testes, produce the male hormone testosterone, as well as sperm cells. Female gonads, or ovaries, make estrogen and progesterone, as well as producing egg cells. While the gonads of both sexes are similar in size and shape and develop from identical fetal tissues, they're quite different in their interior anatomy and function. Ovaries are filled with millions of egg cells from the time of a baby girl's birth, while testes are full of small ducts that begin producing sperm at the onset of puberty.
Ducts
While the gonads produce sex cells, it's the reproductive ducts that are responsible for delivery and housing of those sex cells. In males, the reproductive ducts include the epididymis, the vas deferens, and the seminal vesicles. These collectively move sperm from the testes into the urethra, mix the sperm with seminal fluid, and prepare it for ejaculation. Dr. Gary Thibodeau, in his book "Anatomy and Physiology," explains that the male reproductive ducts develop from fetal tissues called the Wolffian ducts, which develop under the influence of testosterone and wither in its absence. A different set of fetal ducts, called the Mullerian ducts, develop into the female reproductive tract in the absence of testosterone, notes Dr. Thibodeau. These form the uterus and fallopian tubes. The tubes transport an egg from the ovaries to the uterus, which is the receptacle for implantation should fertilization of the egg occur.
External Genitalia
Perhaps the most obvious reproductive organ difference between men and women lies in the appearance of the external genitalia. Despite the fact that a penis and scrotum look so distinct from a set of labia and clitoris, however, Dr. Sherwood explains that these organs arise from identical fetal tissues. Testosterone causes a group of cells to form the head of the male penis, while absence of that hormone leads the cells to become the clitoris in women. Labial cells in female fetuses instead fuse into a single sac---the scrotum---in male fetuses, which eventually houses the testes. The purposes of the external genitalia in men versus women are as distinct as their outward appearances---in men, they are designed to deliver sperm deep into the female reproductive tract, while in women, they allow entry of the penis and protect the opening to the vagina.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
