Biomedicine and Health: Reproductive System

Introduction

The human reproductive system is a group of organs and structures, different in males and females, which allows two people to combine their genetic material and produce offspring. The reproductive system also produces hormones that cause the development of the secondary sexual characteristics such as body shape, facial hair, depth of voice, breasts, and degree of muscle mass. Though not necessary to sustain life, it influences many other organ systems in the body through its production of sex hormones.

The major task of the reproductive system is to produce fertile offspring that will be able to sustain the species. To accomplish this, the organs of the reproductive system produce and mature sex cells, (sperm and ova) transport them to the site of fertilization, and, in females, gestate the fertilized ovum through pregnancy and expel the offspring during birth.

Historical Background and Scientific Foundations

The study of the reproductive system has long been influenced by religious and philosophical ideas. One of the most significant was the longstanding prohibition against human dissection, which was common in the ancient and medieval worlds. Medieval Christianity discouraged study of the reproductive system as a subject that would expose its scholars to sin.

The Greek philosopher Aristotle (384–322 BC) taught that the “superior” male sex provided the impetus for conception by contributing sperm; the female only contributed crude bodily matter. The Romans also approached gender and reproduction from a male-centered point of view, regarding the concept of “female” as simply that which was not fully male, leading to the idea that female reproductive organs were simply inferior versions of male organs. This produced an idea that became dominant idea in the Middle Ages: that both males and females produce semen; the union of these two substances led to conception.

Ancient physicians such as Hippocrates of Cos (460–375 BC) and Galen of Pergamum (AD 129–c.216) used careful observations to inform their opinions about the human reproductive system. Galen, a Greek living in the second century AD, was particularly interested in discovering the details of anatomy through autopsy. Through his work as a physician at a gladiator school, he was able to make great advances in the study of medicine. However, Roman laws against autopsy led to erroneous notions regarding the female reproductive tract. Galen recognized that despite their dissimilar appearance, male and female reproductive organs have parallel functions, including producing reproductive cells. Unfortunately, Galen still adhered to the idea that the female reproductive organs were lesser versions of male organs.

During the period known as late antiquity and the Dark Ages in Europe, the disintegration of the Roman Empire led to a general decline in scholarship. At the same time, however, science and medicine flourished in the Islamic world, where scholars often read (and improved upon) the works of Greek and Roman physicians. These physicians were also bound by a strict ethical code that required them to observe and record symptoms and to use the best treatment. The Iranian physician Avicenna (AD 980–1037) believed that conception was not unlike the process of making cheese: i.e., sperm creates a “clot” in the female's fluid. Several physician authors produced diagrams of the pregnant human body, including Persian physician Mansur ibn Ilyas (fl. late 14th c.).

Although there was sporadic importation of Islamic medical knowledge into Europe during the Middle Ages, much of the work produced at this time relied on philosophy or supposition. Commonly believed inaccuracies stemmed directly from Galen's work and the continuing prohibition against human autopsy. The Renaissance saw some improvement in medical knowledge, likely because authorities, particularly in Italy, allowed a few autopsies. The view of female reproductive organs as a deviation from male norms continued, however, often leading to wild conjecture about their shape and function.

The uterus was a particular object of speculation from the time of the ancient Greeks. It was said to wander throughout the body, spreading noxious fumes and causing a particularly female malady known as “hysteria” (from the Greek hystera, “womb.”) Relying on philosophical ideals, some physicians declared that the womb had several chambers. Some favored two, one for each gender; others seven, for the days of the week. This led to the belief that women could sustain up to seven pregnancies at once, an extremely rare accomplishment even today. The supposed shape of the uterus was determined from the shape of a cow's or horse's uterus, which has two upper “horns,” a feature that the human uterus lacks.

Scholarship began to improve when physicians began to look upon the female reproductive system as something other than a variation of the male. In the mid-sixteenth century, physicians began to question the assumed wisdom of previous generations. The idea of uterine horns fell from favor when French physician Laurent Joubert (1529–1582) wondered why they were so difficult to see. As more attention was paid to the female anatomy, organs were given their own names and their functions were described, rather than being called after male counterparts. In the seventeenth and eighteenth centuries, the study of anatomy led to a greater understanding of both the male and female reproductive systems. By the nineteenth century, established medical colleges and a secure supply of corpses for autopsy led to the solid canon of anatomical data that was received in the twentieth century.

The Urogenital System

The urogenital systems in both males and females develop from early embryonic urogenital ridges composed of mesodermal cells. Although the sex of the embryo is fixed at birth by its sex chromosomes (XX for females and XY for males), for a considerable period in embryonic development, male and female embryos are anatomically ambisexual and thus share a number of features in common.

Gonads—ovaries in females and testes in males—both arise from thickening areas of cells of the urogenital ridge. Initially very much alike in their path of development (the indifferent stage of development), the ultimate development of ovaries and testis is an example of the phenotypic (outward) expression of karyotype or genotype (the actual genes and chromosomes present).

The full development of males and females involves a coordinated series of developmental steps that take place throughout gestation. Throughout the course of development, primitive embryonic structures give rise to sexually characteristic structures. The embryonic Mullerian duct develops into the appendix of the testis in males. In females, the Mullerian duct develops into the uterus, uterine tube, and the cervix, which separates the vaginal canal from the uterus.

In both males and females, an anatomically similar portion of the urogenital sinus, the vesical portion, develops into the urinary bladder. In males, another corresponding region, the pelvic region of the urogenital sinus, develops into the prostatic urethra and a portion of urethra, while in females, it develops into the urethra. The pelvis region of the urogenital sinus develops into the vagina and hymen in the female, and the penile urethra in the male.

The female clitoris and male penis are derived from the same embryological tissue, the genital tubercle. In males, this tissue also develops into penile corpus spongiosum and corpora cavernosa tissue, which when engorged with blood causes penile erection. In females, the clitoris—with smaller amounts of and less developed erectile tissue—is capable of a much smaller erectile state. In males, the scrotum and a portion of the penis (crus of the penis) develop from the ambisexual outer genital folds. In females, the outer genital folds ultimately form the labia majora and crus of the clitoris. The labia minora in females forms from the inner genital folds. In males, the inner genital folds contribute to the development of the penile urethra and corpus spongiosum.

Modern Cultural Connections

Throughout human history discriminatory laws and practices have emphasized the difference between men and women, most often to the distinct disadvantage of women. This long history of speculation contributed to inaccurate folk wisdom and rumors about the reproductive system, some of which persist to this day. Although the phenomenon peaked in the 1890s, the idea of female “hysteria” was treated until the 1940s.

With the rise of mass media culture Western society sought to explore sexuality from multiple perspectives and with a new openness. For example, by establishing a commonality of embryological origins an argument was advanced that the sexual differences between men and women were to be understood in terms cell differentiation and morphological development. Women were not “absent” sexual organs but rather had their own developmental expression of tissues and cells in common with men (e.g. rather than being thought of as absent a penis, the clitoris was properly understood to be the embryological homologue for the male penis). Such studies provide powerful evidence of the commonality of humanity and serve to defeat mystical assertions that men and women are so fundamentally different that social inequities have a fundamental basis in biology “from the moment of conception.”

Yet there is still argument over whether young people should even study human reproduction, lest it cause them to commit immoral acts. Most of the controversy focuses on whether sex education in schools should be taught as “abstinence only” or as some variation of comprehensive sex education. Among the benefits of today's better understanding of the human reproductive system are increased ability to treat disease, lower mortality rates for both mother and baby during childbirth, and the ability to treat some causes of infertility.

See Also Biology: Comparative Morphology: Studies of Structure and Function; Biology: Sociobiology; Biomedicine and Health: Embryology; Biomedicine and Health: Hormonal Regulation of the Body; Biomedicine and Health: Human Gross Anatomy; Biomedicine and Health: Physiology.

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René Nougayrède