reproductive

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reproductive

 [re″pro-duk´tiv]
subserving or pertaining to reproduction.
reproductive organs, female the ovaries, fallopian tubes, uterus, vagina, and vulva (external genitalia) of a female. The breasts are a secondary sex character, enclosing the mammary glands (see also Plates).



The ovaries link the reproductive system to the body's system of endocrine glands. Besides producing the ova, they secrete the female sex hormones estrogen and progesterone, which influence the body's development and general functioning as well as the sexual function. The two ovaries, each about the size of a small plum, lie one on each side of the pear-shaped uterus at its wide upper part. When a female is born, her undeveloped ovaries already contain the specialized cells that can eventually become ova. At puberty these ova begin to ripen, one a month; usually the ovaries alternate in producing them. As the undeveloped egg cell, called a follicle, begins to ripen, it makes its way to the ovary's surface, breaks through its own outer covering, and is released. Release of an egg cell, called ovulation, occurs about once every 28 days.

After its separation from the ovary the ovum is drawn into the nearby fallopian tube through its fringed, flared opening, and is moved along by rhythmic contractions of the tube's walls and by the cilia of its mucous membrane lining. In the course of its passage the ovum ripens fully, and if fertilization occurs it usually takes place while the ovum is moving through the fallopian tube.

The other end of the tube opens directly into the uterus, a muscular organ capable of stretching to contain a fertilized ovum growing through the 9 months of pregnancy. The mucous membrane lining the uterus is also specially adapted to hold the fetus securely and nourish it. When the ovum arrives, the hormones estrogen and progesterone produced in the ovary have previously stimulated the uterus to prepare its lining with extra blood vessels. If the egg has not been fertilized, it loses its vitality, the hormone supply ceases, and the extra blood and tissues are discharged from the body through the vagina, in the menstrual flow. If fertilization has taken place, the growth of a new life has begun; menstruation does not occur, and in fact ceases entirely during the 9 months (approximately 280 days) of pregnancy.

The lower end of the uterus forms an opening called the cervix (neck), which protrudes into the vagina. Enclosed by muscles and lined with mucous membrane, the vagina measures on the average about 8 cm (3 in) in length. In coitus it receives the penis (male copulatory organ) and the discharge of sperm during ejaculation. Like the uterus, the vagina undergoes changes during pregnancy that enable it to stretch to many times its usual size, allowing the infant to pass through it in childbirth.

The exterior opening of the vagina and the surrounding organs make up the vulva; this consists of the labia majora, labia minora, vestibule, and clitoris. Anterior to the vulva is a triangular fatty pad covered with pubic hair, the mons pubis. Between the clitoris and the entry to the vagina is the opening of the urethra, from which urine is excreted. The anus lies to the rear of the vaginal opening. In a virgin, a membrane called the hymen usually closes off a part of the opening to the vagina.

The labia majora envelop the labia minora, and these join together at the clitoris, a diminutive penislike organ that has a purely erotic function. Like the penis, the clitoris has a foreskin and many nerve endings. The vestibule is the area surrounding the entry to the vagina and within the labia minora; at each side of the vaginal opening and elsewhere in the vestibule, glands secrete lubricating fluids to facilitate coitus.

A woman's breasts serve to provide milk for the newborn infant. At puberty the breasts increase in size; during pregnancy they become much larger and start to secrete milk shortly after childbirth.
Disorders of the Female Reproductive Organs. Bacterial and other infections, tumors, and birth injuries can affect the female reproductive tract and organs. Growths or tumors can develop in any part of the tract; they are usually benign and may not require treatment but should be examined periodically in case they grow large and affect the organs, or become malignant. The most prevalent bacterial diseases of a woman's reproductive organs are the venereal diseases (diseases usually contracted during coitus). The most serious of these are syphilis and gonorrhea.
reproductive organs, male the external genitalia, accessory glands that secrete special fluids, and the accompanying ducts in the male (see also Plate 13).
External Genitalia. These include the penis, testes, and scrotum. The penis is the organ through which semen is transferred into the female during coitus; semen is a carrier for the spermatozoa produced in the testes. The testes also produce the male hormone testosterone, which gives a sexually mature male his distinctively masculine characteristics and his sexual energy and drive. The testes are suspended from the spermatic cord, which also connects the testes with the other parts of the reproductive system. This cord consists of blood vessels, nerves and ducts, all enclosed in connective tissue.
Accessory Glands. The accessory reproductive glands include the prostate, two seminal vesicles, and two bulbourethral glands (also known as Cowper's glands). The prostate is located below and against the urinary bladder and completely surrounds the urethra. It produces a thin, clear, slightly alkaline fluid that neutralizes the normal acidity of the urethra caused by the continual passage of urine and enables the spermatozoa to pass through the urethra unharmed. The seminal vesicles are two glands located just above and to the rear of the prostate; they consist of many small sacs, or pockets, in which is produced and stored the thick, milky fluid that is ejaculated during the male orgasm. The fluid serves as the carrier for the sperm and is the major constituent of the semen. The two bulbourethral glands, about the size of peas, secrete a clear, sticky fluid that lubricates the urethra and makes it easier for the semen to pass through it during the process of ejaculation.
Ducts. The spermatozoa are led from the testes to the urethra through a system of ducts. First is a convoluted tube (one on top of each testis and connected directly to it), called an epididymis, where mature spermatozoa produced in the testes are stored. Each epididymis is connected to a ductus deferens (called also vas deferens), a part of the spermatic cord that conducts the spermatozoa to the duct lying close to the bladder. These ducts join with ducts leading from the seminal vesicles just before the urethra; the combined duct, called the ejaculatory duct, passes through the prostate and joins with the urethra. The urethra then conducts the semen through the penis.
Discharge of Semen. The tissues that form the mass of the penis are called erectile tissue. This tissue is spongy in nature and filled with innumerable hollow spaces. There is also a network of veins and arteries within the penis. Sexual excitement causes the muscles surrounding the veins to contract, thereby restricting the flow of blood from the penis. At the same time, the muscles surrounding the arteries relax, permitting the free flow of blood into the penis at the full pressure of the circulatory system. The result is that the spongy tissue fills with blood and the penis swells in size and becomes stiff and erect.



Sexual excitement also stimulates the accessory glands to secrete larger amounts of their fluids. When the sexual tension becomes acute enough, as a result of coitus, masturbation, or purely mental stimulation (as in nocturnal emissions or “wet dreams”), there is a series of reflex contractions of the reproductive organs. The muscles surrounding the seminal ducts, the prostate, and the seminal vesicles contract convulsively; this causes the semen to be ejaculated forcibly from the penis. There is first an ejaculation of the fluid from the prostate, followed immediately by the semen. About 2 or 3 ml of semen are ejaculated. This volume of semen is believed to contain between 200 and 500 million sperm, only one of which is necessary to fertilize the ovum.
Disorders of the Male Reproductive Organs. For disorders that affect particular organs, see penis, prostate, and cryptorchidism. Since the male reproductive organs are connected so closely with each other, an infection in one is likely to spread throughout the entire reproductive system. This is particularly true of venereal diseases (those usually contracted through coitus), such as syphilis and gonorrhea.

re·pro·duc·tive

(rē'prō-dŭk'tiv),
Relating to reproduction.

reproductive

(rē′prə-dŭk′tĭv)
adj.
Of, relating to, or capable of reproduction: reproductive organs.
n.
Zoology A reproductive organism, especially a sexually mature social insect.

re′pro·duc′tive·ly adv.
re′pro·duc′tive·ness n.

reproductive

[rē′prəduk′tiv]
Etymology: L, re + producere, to produce
pertaining to the process of reproduction.

reproductive

subserving or pertaining to reproduction.

reproductive behavior
see sexual behavior.
reproductive cycle
in all mammalian species other than humans the reproductive cycle is an estrous cycle.
reproductive efficiency
fertility or efficiency in terms of input, e.g. services per conception, bull serving capacity estimates.
reproductive failure
infertility; failure to produce viable offspring; the end-stage of reproductive inefficiency.
reproductive fitness
a pre-mating examination of cows in an intensive herd health program; includes manual examination of genitalia per rectum, cervical sample for microbiological examination, blood sample for locally relevant abortogenic diseases, manual examination of udder, milk cell count and composite bacteriological examination of milk.
reproductive history
computerized or card-based record of individual cow's complete breeding record including all services and identity of donor or naturally mated bull.
reproductive organs (female)
the ovaries, which produce the ova, or eggs; the uterine tubes; the uterus; the vagina, or birth canal; and the vulva, comprising the external genitalia. The udder is a secondary sex character, enclosing the mammary glands.
reproductive organs (male)
the testes, external genitalia and accessory glands that secrete special fluids and the ducts through which these organs and glands are connected to each other and through which the spermatozoa are ejaculated during coitus.
reproductive performance
the productivity of the animal or herd or flock in terms of offspring produced, can be expressed in many ways, e.g. live piglets per litter or per year or per sow-year or per cubic meter of shed space.
reproductive rate
viable, full-term offspring produced per female per year.
reproductive senescence
the end of cyclic reproductive activity in primates; not recognized in domestic animals.
reproductive system
the genital tract plus the endocrinal control systems, especially the hypothalamus, pituitary, gonads and placenta, the products of pregnancy and the mammary glands.
reproductive tract
see reproductive organs (above).