Female Reproductive System
Reproduction is the process by which organisms produce more organisms like
themselves. All living things, including humans, reproduce: it's one of the things that set
us apart from nonliving matter. And because all living things eventually die, new
creatures of the same kind must constantly be born to perpetuate a particular species.
Interestingly, although the reproductive system is essential to keeping a species alive,
unlike other body systems, it is not essential to keeping an individual being alive.
How Is the Female Reproductive System Important for Living?
Without the female reproductive system, there would be no perpetuation of life. Although
the female is dependent on the male for fertilization of her egg, it is she who carries the
offspring through pregnancy and childbirth. Through the reproduction process, children
are born, and families are continued. If people didn't reproduce, families would die out
and the human race would cease to exist.
Humans, like other organisms, transmit certain characteristics of themselves to the next
generation through their genes, the special carriers of human traits. The genes parents
pass along to their children are what make children similar to others in their family, but
they are also what make each child unique. These genes come from the father's sperm and
the mother's egg, which are produced by their respective reproductive systems.
Basic Anatomy
Most species have male and female organisms. Each sex has its own unique reproductive
system. They are different in shape and structure, but both are specifically designed to
produce, nourish, and transport either the egg or sperm.
Unlike its male counterpart, the female reproductive system is almost entirely hidden
within the pelvis. It consists of organs that enable a woman to produce eggs (ova), to
have sexual intercourse, to nourish and house the fertilized egg (ovum) until it is fully
developed, and to give birth.
Females also have external organs collectively called the vulva (which means
"covering"). Located between the legs, the outer parts of the vulva cover the opening to a
narrow canal called the vagina. The fleshy area located just above the top of the vaginal
opening is called the mons pubis. A thin sheet of tissue called the hymen partially covers
the opening of the vagina. Two pairs of skin flaps, the labia (which means "lips")
surround the vaginal opening. The clitoris, which is located toward the front of the vulva
where the folds of the labia join, is a small cylindrical structure similar to the male penis;
it also contains erectile tissue. Inside the labia are openings to the urethra (the canal that
carries urine from the bladder to the exterior of the body) and vagina. The outer labia and
the mons pubis are covered by pubic hair in the sexually mature female.
The female internal organs are the vagina, uterus, fallopian tubes, and ovaries. The
vagina is a 3- to 6-inch-long tubular structure that extends from the vaginal opening to
the uterus. It has muscular walls lined with mucous membrane, and it serves as the
female organ of copulation (sexual intercourse) as well as the birth canal. It connects with
the uterus, or womb, which houses the fetus during pregnancy. About 3 inches long and
2 inches wide and shaped like an inverted pear, the uterus is a muscular, expandable
organ with thick walls.
At the lower part of the uterus is the cervix, which opens into the vagina. At the upper
part, the fallopian tubes connect the uterus with the ovaries, two oval-shaped organs that
lie to the right and left of the uterus. They produce, store, and release eggs through the
fallopian tubes into the uterus. The ovaries also produce the hormones estrogen and
progesterone. Also part of the reproductive system are the breasts. Mammary glands
inside the breasts secrete milk after childbirth.
Normal Physiology
The organs of sexual reproduction are the gonads, which are the ovaries in females and
the testes in males. Females produce female gametes, or eggs; males produce male
gametes, or sperm. Sexual reproduction is the fertilization of a female gamete by a male
gamete. When a female is born, each of her ovaries has hundreds of thousands of eggs,
but they remain dormant until her first menstrual cycle, which occurs during puberty. At
this time, during adolescence, the pituitary gland secretes hormones that stimulate the
ovaries to produce female sex hormones, including estrogen, which helps the female
develop into a sexually mature woman.
Also at this time, females begin releasing eggs as part of a monthly period called the
menstrual cycle. Approximately once a month, during ovulation, an ovary discharges a
tiny egg that reaches the uterus through one of the fallopian tubes. Unless fertilized by a
sperm while in the fallopian tube, the egg dries up and is expelled about 2 weeks later
from the uterus during menstruation. Blood and tissues from the inner lining of the uterus
combine to form the menstrual flow, which usually lasts from 3 to 5 days.
If a female and male have sexual intercourse within several days of ovulation,
fertilization can occur. When the male ejaculates, about one tenth of an ounce of semen is
deposited into the vagina. Between 200 and 300 million sperm are in this small amount of
semen, and they "swim" up from the vagina through the cervix and uterus to meet the egg
in the fallopian tube. It takes only one sperm to fertilize the egg.
About a week after the sperm fertilizes the egg, the fertilized egg has become a
multicelled blastocyst, a pinhead-sized hollow ball with fluid inside, now housed in the
uterus. The blastocyst burrows itself into the lining of the uterus, called the endometrium.
Estrogen causes the endometrium to thicken and become rich with blood, and
progesterone, another hormone released by the ovaries, maintains the thickness of the
endometrium so that the blastocyst can attach to the uterus and absorb nutrients from it.
This process is called implantation.
As cells from the blastocyst take in nourishment, the embryonic stage of development
begins. The inner cells form a flattened circular shape called the embryonic disk, which
will develop into a baby. The outer cells become thin membranes that form around the
baby. The embryonic cells multiply thousands of times, move to new positions, and
eventually become the embryo. After approximately 8 weeks, the embryo is about the
size of an adult's thumb, but all of its parts - the brain and nerves, the heart and blood, the
stomach and intestines, and the muscles and skin - have formed.
During the fetal stage, which lasts from 9 weeks after fertilization to birth, development
continues as cells multiply, move, and differentiate. The fetus floats in amniotic fluid
inside the amniotic sac. Its oxygen and nourishment come from the mother's blood via the
placenta, a disk-like structure that adheres to the inner lining of the uterus and is
connected to the umbilical cord. The umbilical cord attaches the embryo at its navel to
the mother's uterus. The umbilical arteries in the cord carry blood from the fetus to the
placenta, and an umbilical vein returns blood from the placenta to the fetus. The amniotic
fluid and membrane cushion the fetus against bumps and jolts to the mother's body.
Pregnancy lasts an average of 266 days. When the baby is ready for birth, its head presses
on the cervix, which begins to relax and widen to get ready for the baby to pass into and
through the vagina, which has enlarged to become the birth canal. The mucus that has
formed a plug in the cervix loosens, and with amniotic fluid, comes out through the
vagina when the mother's "water" breaks.
When contractions begin, the uterine walls contract as they are stimulated by the pituitary
hormone oxytocin. The contractions cause the cervix to widen and begin to open. After
several hours of this widening, the cervix is dilated (opened) enough for the baby to come
through. The baby is pushed out of the uterus, through the cervix, and along the birth
canal. The baby's head usually comes first; the umbilical cord comes out with the baby
and is cut after the baby is delivered.
The last stage of the birth process involves the delivery of the placenta, which is now
called the afterbirth. It has separated from the inner lining of the uterus, and through
further contractions of the uterus it is expelled with its membranes and fluids.
Diseases, Conditions, Disorders, and Dysfunctions
Like all body systems, the female reproductive system is at risk for certain diseases and
conditions. The following are some examples.
Disorders of the Vulva and Vagina
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Vulvovaginitis, an inflammation of the vulva and/or vagina, is the most common
childhood gynecological problem. In young girls, it is most often caused by
irritating substances (such as laundry soaps or bubble baths), and may be
exacerbated by poor personal hygiene (such as wiping from back to front after a
bowel movement). Symptoms include redness and itching in the vaginal area and
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sometimes vaginal discharge. Vulvovaginitis can also be caused by an overgrowth
of candida, a yeast-like fungus normally present in the vagina, although yeast
infections are more common in teenagers and adults.
Vaginal bleeding, when it occurs in premenstrual girls, is most commonly due to
the presence of a foreign body in the vagina, such as wadded-up toilet paper. Less
often it may be due to urethral prolapse, a condition in which the mucous
membranes of the urethra protrude into the vagina and form a mass that bleeds
easily. It can also be due to an injury or sexual abuse.
Labial adhesions, the adherence (sticking together) of the labia in the midline,
usually appears in infants and young girls. Although there are usually no
symptoms associated with the condition, labial adhesions can lead to an increased
risk of urinary tract infection. It is sometimes treated with a topical estrogen
cream to help separate the labia.
Disorders of the Ovaries
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Tumors, although relatively rare in childhood, can occur. In adolescents, the most
common type of gynecological tumor is the ovarian teratoma, and it may be either
benign or malignant. Tumors are usually detectable as masses in the abdomen and
may be accompanied by abdominal pain; they are usually removed surgically.
Ovarian cysts are noncancerous sacs filled with fluid or semi-solid material.
Although they are common and generally harmless, they can become a problem if
they grow very large. Large cysts may push on surrounding organs, causing
abdominal pain. In most cases, cysts will disappear spontaneously and treatment
is unnecessary. However, if the cysts are painful, birth control pills may be used
to alter their growth, or they may be removed surgically.
Ovarian torsion, or twisting of the ovary, is a fairly uncommon condition that
can occur when an ovary becomes twisted or because of a developmental
abnormality or disease. This blocks blood from flowing through the blood vessels
that supply and nourish the ovaries. The most common symptom is lower
abdominal pain. Surgery is usually necessary to correct the condition.
Polycystic ovary syndrome is a hormonal disorder in which an overproduction
of male hormones (androgens) by the ovaries causes the ovaries to become
enlarged and develop fluid-filled sacs, or cysts. It often first appears during
adolescence, and associated problems may include obesity, acne, erratic menstrual
periods, and the appearance of masculine characteristics such as hair growth on
the face and chest. Depending on the type and severity of the condition, it may be
treated with drugs that work against the effects of the male hormones and possibly
birth control pills to regulate hormone balance and menstruation. It is associated
with a higher risk of infertility later in life, particularly if untreated.
Menstrual problems. Both common and varied, menstrual problems range from
dysmenorrhea (painful periods) and menorrhagia (heavy periods) to oligomenorrhea
(missed and/or infrequent periods). Treatments may include pain medication and
hormone pills.
Sexually transmitted diseases. These include infections and diseases such as HIV/AIDS
(Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome), human
papiloma virus (HPV, or genital warts), syphilis, chlamydia, gonorrhea, and herpes
genitalis. They are spread from one person to another by sexual intercourse and other
genital contact involving the sexual organs and other body parts.
Toxic shock syndrome. This rare illness is caused by a bacterial infection that is more
likely to develop if a tampon is left in too long. It can produce high fever, diarrhea,
vomiting, and shock.
Glossary
afterbirth: Placenta and fetal membranes that are expelled after delivery.
amniotic fluid: Fluid in the amniotic sac, the membrane that surrounds the developing
fetus.
blastocyst: Early stage of embryo development; pinhead-sized hollow ball with fluid
inside.
cervix: Lower end of the uterus that opens into the vagina.
clitoris: Small cylindrical structure at the top of the vaginal opening; contains erectile
tissue similar to the male penis.
egg: Female sex cell; also called an ovum.
embryo: The developing human from the time of implantation to the end of the eighth
week after conception.
endometrium: Inner lining of the uterus.
fallopian tubes: Tubes through which eggs (ova) pass from the ovaries to the uterus.
fertilization: The joining of male and female sex cells (ovum and sperm) to form a new
organism.
fetus: Developing human from the ninth week after conception until birth.
gamete: Sex cell that joins with another gamete of the opposite sex to produce a new
organism.
gonads: Sex organs that contain the gametes and produce sex hormones.
hymen: Thin tissue that partially covers the vaginal opening.
implantation: The process of attachment of the embryo to the inner wall of the uterus.
labia: Two pairs of skin flaps surrounding the vaginal opening.
mammary glands: Milk-producing glands in the female breasts.
menstrual cycle: Monthly maturation and release of an egg (ovum) from an ovary.
mons pubis: Fleshy area located just above the top of the vaginal opening.
ovaries: Structures in which female eggs (ova) are located.
ovulation: Release of a mature egg (ovum) from an ovary.
oxytocin: Hormone that stimulates contractions in the uterus during the birth process.
placenta: Structure attached to the umbilical cord that provides nourishment for the
developing fetus and removes its waste by an exchange with the mother's bloodstream.
semen: Fluid containing sperm that is ejaculated by the male.
sperm: Male sex cell(s).
urethra: Canal that carries urine from the bladder to the exterior of the body.
uterus: Muscular, pear-shaped internal female reproductive organ in which the embryo
and fetus develop during pregnancy; also called the womb.
vagina: Muscle-walled tube that serves as the birth canal and entrance to the internal
female reproductive tract.
vulva: Female external sex organs.