Structure and Functions (Magill’s Medical Guide, Sixth Edition)
The reproductive system in each sex includes the organs that produce the gametes, called the gonads, and those that transport the gametes. In addition, the female mammary glands are also considered reproductive organs since they produce milk to nourish the newborn, a critical step in survival of the species.
The male gonads are the testes, which are located within the scrotum, a pouch of skin and muscle that is suspended from the body wall. In the adult, each egg-shaped testis measures about 2.5 centimeters by 4.0 centimeters. Internally, the testes contain seminiferous tubules, hollow tubes in which the sperm develop. Besides the sperm cells, the seminiferous tubules also contain Sertoli cells, large cells in which the developing sperm are embedded. The Sertoli cells produce hormones, pass nutrients to the sperm, protect them from blood-borne toxins, and control their development. In spaces between adjacent seminiferous tubules are the interstitial cells of Leydig, which produce testosterone and other hormones.
Lying near each testis within the scrotum is the epididymis. Sperm undergo several stages of development within the testis, then move into the epididymis, where they proceed through further steps in maturation, including the development of the swimming ability that is necessary for fertilization of an ovum.
The narrow end of the epididymis is continuous with the long (45-centimeter) tubule...
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Disorders and Diseases (Magill’s Medical Guide, Sixth Edition)
Abnormalities may exist in either the male or the female reproductive tract as a result of deviations during embryonic development, injury, or disease. Anatomical abnormalities in the reproductive system often can be corrected surgically.
In hypospadias, a problem during embryonic development of the male reproductive organs causes the urethral opening to be on the underside of the penis rather than at its tip. Hypospadias can occur independently or can be a sign of more serious problems. Urethral stricture or stenosis refers to a narrowing of the urethra; this can occur anywhere along its length, from the tip of the penis back to the prostate gland. Urethral stenosis causes difficulty in urination; it may be present from birth or result from later damage or infection. Cryptorchidism is the presence of one or both testes in the abdominal cavity instead of in the scrotum. In the male embryo, the testes begin development in the body cavity near the kidneys and then migrate into the scrotum during the last month or two before birth. In some male infants born with undescended testes, the testes will spontaneously move into the scrotum shortly after birth. If not, then the cryptorchidism must be corrected surgically, usually within the first year of life, in order to prevent later infertility and other complications.
In females, problems during embryonic development can also lead to malformed reproductive organs. The...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Rituals involving alteration of the reproductive organs have been performed since ancient times. Castration (removal of the testes) has been carried out for various reasons. In early times, men who were guards of noble women were castrated to control their sexual activity. During the Renaissance, castration of boys was performed to produce singers who would retain their clear, high-pitched voices, since it is testosterone that causes the deepening of the voice at puberty. More recently, castration has been espoused as a “treatment” for habitual rapists: Some judges sentence convicted sex offenders to castration, despite the fact that many authorities believe that rape is a manifestation of violent tendencies, rather than the result of excessive sexual desire.
In the United States and elsewhere, it is common for boys to undergo circumcision, or the removal of the foreskin, a flap of tissue that covers the glans of the penis. Parents have their sons circumcised in order to conform to religious and cultural practices. In the United States, the procedure is usually performed shortly after the boy’s birth, but in other cultures circumcision may occur during puberty rituals. One rationalization for performing circumcision is that removal of the foreskin helps to prevent the buildup of smegma, a thick secretion produced by glands located under the base of the foreskin. In fact, some studies have shown that...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Ammer, Christine. The New A to Z of Women’s Health: A Concise Encyclopedia. 6th ed. New York: Checkmark Books, 2009. A respected classic that covers the full spectrum of women’s health issues, including reproduction, the aging process, methods of contraception, childbearing, and advances in infertility research and hormone therapy. Includes helpful charts and illustrations.
Berek, Jonathan S., ed. Berek and Novak’s Gynecology. 14th ed. Philadelphia: Lippincott Williams & Wilkins, 2007. A standard text covering all aspects of gynecology with an emphasis on diagnosis and treatment. Topics include biology and physiology, family planning, sexuality, early pregnancy loss, malignant diseases of the reproductive tract, and breast cancer.
Jones, Richard E., and Kristin H. Lopez. Human Reproductive Biology. 3d ed. Burlington, Mass.: Academic Press/Elsevier, 2006. This college-level textbook provides comprehensive coverage of all biological aspects of human reproduction.
Manassiev, Nikolai, and Malcolm I. Whitehead, eds. Female Reproductive Health. New York: Parthenon, 2004. Blending basic science with clinical information, this text covers the entire range of reproductive health. Topics include anatomy and physiology, sexually transmitted diseases, hormone therapy, breast conditions, and sexual function and dysfunction, among many others.
Marieb, Elaine N....
(The entire section is 396 words.)
Reproductive System (Encyclopedia of Science)
The reproductive system is a group of organized structures that make possible the creation, or reproduction, of new life for continuation of a species. Human reproduction is sexual, meaning that both a male and a female contribute genetic material in the creation of a new individual. During puberty, usually occurring between the ages of nine and fourteen, the reproductive systems of both sexes mature. The ovaries of a female release eggs (female sex cells) and a male's testes produce sperm (male sex cells). Reproduction occurs when a sperm unites with an egg, a process called fertilization.
The male reproductive system
The main tasks of the male reproductive system are to produce sperm cells and to introduce sperm into the female reproductive tract. Sperm are produced in the testes, the pair of male reproductive glands located in the scrotum, a skin-covered sac that hangs from the groin. Within each testis are hollow tubules called seminiferous tubules where sperm cells are produced. The testes also secrete the male hormone testosterone, which stimulates development of the reproductive structures and secondary sexual characteristics (such as deepened voice) at puberty.
After production, sperm cells move to a highly coiled tube called the epididymis, where they mature and are stored. During ejaculation (the ejection of sperm from the penis...
(The entire section is 997 words.)