SIKLUS
MENSTRUASI
Pubertas tercapai pada usia 12-16 tahun dipengaruhi oleh
keturunan, bangsa, iklim & lingkungan. Pertama kali menstruasi disebut
dengan menarche. Pertumbuhan payudara pertama kali disebut thelarche.
Tumbuhnya rambut kemaluan disebut dengan pubarche.
Siklus menstruasi normal dapat dibagi menjadi 2 segmen
yaitu, siklus ovarium (indung telur) dan siklus uterus (rahim). Siklus indung
telur terbagi lagi menjadi 2 bagian, yaitu siklus folikular dan siklus luteal,
sedangkan siklus uterus dibagi menjadi masa proliferasi (pertumbuhan) dan masa
sekresi.
Sistem hormonal yang mempengaruhi siklus menstruasi adalah:
- FSH-RH
(follicle stimulating hormone releasing hormone) yang dikeluarkan
hipotalamus untuk merangsang hipofisis mengeluarkan FSH
- LH-RH
(luteinizing hormone releasing hormone) yang dikeluarkan hipotalamus untuk
merangsang hipofisis mengeluarkan LH
- PIH
(prolactine inhibiting hormone) yang menghambat hipofisis untuk
mengeluarkan prolaktin
Gambar Siklus Hormonal
SIKLUS
MENSTRUASI
Menstruasi
dipengaruhi oleh :
Gn RH Ã merangsang pelepasan FSH, LH,
prolaktin
Prolaktin Ã
prod. o/ sel α
hipofisis ant., memulai & mempertahankan prod. progesteron
FSH & LH Ã
prod. o/ sel β
hipofisis ant.,sekresi estrogen
Estrogen & Progesteron Ã
mempengaruhi perubahan endometrium
Siklus
ini dibagi menjadi 4 tahap, yaitu :
1.
STADIUM
MENSTRUASI
•
Endometrium
mengalami peluruhan sehingga menyebabkan perdarahan. Lapisan yg tertinggal
disebut stratum basale, berlangsung selama 4 hari.
•
Saat haid akan
keluar darah, potongan-potongan endomettrium & lendir serviks
•
Darah tidak
membeku karena ada fermen yang mencegah pembekuan darah & mencairkan
potonga-potongan mucosa
•
Banyaknya darah
keluar selama haid normal ±50 cc
2.
STADIUM
PROLIFERASI (5-14)
Dibagi menjadi 2 tahap :
a.
Proliferasi
Dini
·
Endometrium
tumbuh tebal ± 2 mm
·
Kelenjar lurus,
epitelnya kubus rendah, intinya basal
b.
Stadium
Proliferasi Lanjut
·
endometrium
lebih tebal karena bertambahnya stroma akibat pemecahan sel-sel
3.
STADIUM SEKRESI
(14-28)
a.
Sekresi Dini
·
Lebih tipis
dari fase sebelumnya
·
Hal ini karna
kehilangan cairan, tebalnya ± 4-5 mm
·
endometrium
sudah dapat dibedakan :
(stratum
compactum) saluran kelenjar yang sempit, lumennya berisi sekret, stroma
yang berlebihan & memperlihatkan oedem
(stratum
spongiosum) banyak lubang-lubangnyaà terdapat rongga dari kelenjar-kelenjar yang banyak,
melebar & berkelok-kelok dengan stroma yang sedikit diantaranya
stratum basale berbatasan
dengan otot, inaktif kecuali mitosis pada kelenjar
b.
Sekresi Lanjut
·
tebalnya ± 5-6
mm
·
Ada peningkatan
dari fase sebelumnya, dimana endometrium menjadi sangat vaskuler, kelenjar
berkelok-kelok & kaya glikogen
·
Ideal untuk
nutrisi & perkembangan ovum
·
Sel stroma
sitoplasmanya bertambah
·
Ibu hamil à stroma à desidua akibat
pengaruh progesteron
4.
STADIUM PRE
MENSTRUIL
·
Stroma
mengalami disintegrasi, dgn hilangnya cairan & sekret maka terjadi kolaps
dari kelenjar & arteri à terjadi vasokonstriksi à mengalami relaksasi à pecah
·
Masa dari hari
pertama haid sampai hari pertama haid berikutnya disebut siklus
·
Siklus haid
normal 28 hari (3-5 mg)
·
Lama haid ± 4-5
hari
SIKLUS OVARIUM
Ovarium merupakan organ reproduksi wanita terletak di dalam tubuh, dilapisi
oleh selapis sel epitel dan jaringan ikat padat disebut tunika albugenia.
Ovarium mempunyai jaringan penggantung disebut mesovarium.
Fungsi Ovarium:
1.
Sebagai kelenjar eksokrin
menghasilkan sel telur atau ovum
2.
Sebagai kelenjar endokrin
menghasilkan hormon estrogen dan progesteron
Pengaruh
Hormon dalam Oogenesis
Kelenjar hipofisis mengeluarkan
hormon Folikel Stimulating Hormon (FSH) yang merangsang pertumbuhan
sel-sel folikel di sekeliling ovum. Ovum yang matang diselubungi oleh sel-sel
folikel yang disebut Folikel de Graaf,
Folikel de Graaf mengeluarkan hormon estrogen. Hormon
estrogen merangsang kelenjar hipofisis untuk mensekresikan hormon Luitinizing
Hormon (LH), hormon LH merangsang terjadinya ovulasi.
Selanjutnya folikel yang sudah
kosong dirangsang oleh LH membentuk badan kuning atau korpus luteum
Korpus luteum mengeluarkan hormon
progresteron yang berfungsi menghambat sekresi FSH dan LH
Kemudian korpus luteum mengecil dan
hilang, sehingga akhirnya tidak membentuk progesteron lagi, akibatnya FSH mulai
terbentuk kembali, proses oogenesis mulai kembali.
·
Follicle Stimulating Hormone (FSH)
- Oosit
awalnya dilapisi oleh folikel primordial. Sel folikel akan mengadakan
proliferasi sehingga terbentuk beberapa lapisan.
- oosit
dilapisi 1 lapis sel folikel à folikel primer,
- 2
lapis à folikel sekunder,
- 3
lapis /> Ã folikel tersier
- antara
ovum dengan sel folikel terdapat ruang/rongga yang disebut antrum fase ini
disebut folikel de Graaf.
·
Luteinizing hormone (LH)
- LH
bersama-sama dengan FSH akan merangsang pematangan ovum dan ovulasi
· Estrogen
(hormon ovarium)
- Fungsi estrogen: proliferasi dan penebalan dinding
endometrium & sel-sel spesifik di dalam tubuh yang bertanggung jawab
pada perkembangan karakteristik seks sekunder wanita, seperti pembesaran
payudara, pinggul, tumbuh rambut pada alat vital dan di ketiak.
- Estrogen = hormon seks wanita, dibawah pengaruh
hormon ini terjadi penebalan dinding endometrium, sehingga fase ini
disebut fase proliferasi.
- Efek estrogen
Pubertas :
ü merangsang
pertumbuhan organ reproduksi internal, genetalia eksterna dan mammae
ü merangsang
pertumbuhan rambut tubuh
ü merangsang
pertumbuhan tulang panjang dan penutupan dini epifise
ü merangsang
distribusi lemak wanita
·
Progesteron
·
Dibentuk oleh
korpus luteum setelah terjadi ovulasi
·
Dapat diisolir
kecuali dari plasenta juga dari kelenjar suprarenalis dan darah yang berasal
dari V. Ovarica
·
Kadar tertinggi
pada urine dijumpai pada hari ke-20-21 setelah M dan menurun sampai hilang 2
hari sebelum M
·
Pengaruh terhadap uterus :
Endometrium
bersekresi ® tebal dan oedematus ® mempermudah nidasi
Fase sekresi ® endometrium tertimbun glikogen dan
mineral (Ca) penting untuk makan ovum dan mempertahankan kehamilan (kalau
kurang ®mudah abortus)
Terhadap dinding uterus :
mengurangi kontraksi dari pengaruh
oksitosin
·
Terhadap mammae
: pertumbuhan acini dan lobuli kelenjar
mammae seperti pada fase post ovulatoir dan selama kehamilan
·
Rangsangan sekresi kelenjar
endometrium
·
Induksi mukus cervix yang kental
& lengket
·
Menurunkan proliferasi sel epitel
vagina
·
Menghambat efek “milk – inducing”
dari prolaktin
·
Memberikan efek feedback pada
hipotalamus dan hipofisis anterior.
Menstruasi Ovulatoir adalah
menstruasi yang didahului oleh ovulasi (M yang normal). Menstruasi
Anovulatoir adalah menstruasi tanpa didahului ovulasi (tidak terjadi
korpus luteum dan pembentukan progesteron) ® endometrium tetap dalam stadium
proliferasi sampai terjadi Menstruasi.
http://missheni.blogspot.com/2011/01/siklus-menstruasi.html
The Reproductive System of the
Female
A woman's reproductive system produces
sex hormones and functional gametes and also must be able to protect and
support a developing embryo and nourish the newborn infant. The principal
organs of the female reproductive system are the ovaries , the uterine tubes ,
the uterus , the vagina , and the components of the external genitalia
As in males, a variety of accessory
glands release their secretions into the female reproductive tract.
The ovaries, uterine tubes, and uterus are enclosed within an extensive
mesentery known as the broad ligament . The uterine tubes run along the
superior border of the broad ligament and open into the pelvic cavity lateral
to the ovaries. The mesovarium, a thickened fold of mesentery, supports and
stabilizes the position of each ovary.
Several other ligaments assist the
broad ligament in supporting and stabilizing the position of the uterus and
associated reproductive organs. These ligaments lie within the mesentery sheet
of the broad ligament and are connected to the ovaries or uterus. The broad
ligament limits side–to–side movement and rotation, and the other ligaments
(described in our discussion of the ovaries and uterus) prevent superior–
inferior movement.
The Ovariesare small, lumpy,
almond–shaped organs near the lateral walls of the pelvic cavity. The ovaries
perform three main functions: (1) produce immature female gametes, or oocytes,
(2) secrete female sex hormones, including estrogens and progestins, and (3)
secrete inhibin, involved in the feedback control of pituitary FSH
production.
A typical ovary is a flattened oval
about 5 cm in length, 2.5 cm in width, and 8 mm in thickness and weighs 6–8 g
(roughly 0.25 oz). An ovary is pink or yellowish and has a nodular consistency.
The visceral peritoneum, or germinal epithelium , covering the surface of each
ovary consists of a layer of columnar epithelial cells that overlies a dense
connective–tissue layer called the tunica albuginea .
We can divide the interior tissues, or stroma ,
of the ovary into a superficial cortex and a deeper medulla. Gametes are
produced in the cortex.
Oogenesis
Ovum production, or oogenesis begins before a
woman's birth, accelerates at puberty, and ends at menopause
Between puberty and menopause,
oogenesis occurs on a monthly basis as part of the ovarian cycle .
Unlike spermatogonia, the oogonia, or stem
cells of females, complete their mitotic divisions before birth. Between the
third and seventh months of fetal development, the daughter cells, or primary oocytes , prepare to undergo meiosis. They
proceed as far as the prophase of meiosis I, but at that time the process comes
to a halt. The primary oocytes then remain in a state of suspended development
until the individual reaches puberty, when rising levels of FSH trigger the
start of the ovarian cycle. Each month thereafter, some of the primary oocytes
will be stimulated to undergo further development. Not all primary oocytes
produced during development survive until puberty. The ovaries have roughly 2
million primordial follicles at birth, each containing a primary oocyte. By the
time of puberty, the number has dropped to about 400,000. The rest of the
primordial follicles degenerate in a process called atresia.
Although the nuclear events under way in the ovaries during meiosis are the
same as those in the testes, the process differs in two important details:
The cytoplasm of the primary oocyte
is unevenly distributed during the two meiotic divisions. Oogenesis produces
one functional ovum, which contains most of the original cytoplasm, and two or
three polar bodies , nonfunctional cells that
later disintegrate
The ovary releases a secondary oocyte rather than a mature ovum. The
secondary oocyte is suspended in metaphase of meiosis II; meiosis will not be
completed unless and until fertilization occurs.
Oogenesis.
In oogenesis, a single primary oocyte produces an ovum and two or three
nonfunctional polar bodies.
The Ovarian Cycle
Ovarian follicles are specialized structures
in which both oocyte growth and meiosis I occur. The ovarian follicles are
located in the cortex of the ovaries. Primary oocytes are located in the outer
portion of the ovarian cortex, near the tunica albuginea in clusters called egg
nests .
After sexual maturation, a different
group of primordial follicles is activated each month. This monthly process is
known as the ovarian cycle .
The ovarian cycle can be divided into a follicular
phase , or preovulatory phase , and a luteal
phase , or postovulatory phase .
Follicle formation is stimulated by
FSH from the anterior pituitary gland. The ovarian cycle begins as activated
primordial follicles develop into primary follicles .
In a primary follicle, the follicular cells enlarge and undergo repeated
divisions that create several layers of follicular cells around the oocyte.
These follicle cells are now called granulosa cells .
As layers of granulosa cells develop
around the primary oocyte, microvilli from the surrounding granulosa cells
intermingle with those of the primary oocyte. The microvilli are surrounded by
a layer of glycoproteins; the entire region is called the zona pellucida . The microvilli increase the surface
area available for the transfer of materials from the granulosa cells to the
rapidly enlarging oocyte.
The conversion from primordial to
primary follicles and subsequent follicular development occurs under FSH
stimulation. As the granulosa cells enlarge and multiply, adjacent cells in the
ovarian stroma form a layer of thecal cells around
the follicle. Thecal cells and granulosa cells work together to produce sex
hormones called estrogens .
The Formation of Secondary
Follicles. Although many primordial follicles develop into primary follicles,
only a few will proceed to the next step. The transformation begins as the wall
of the follicle thickens and the granulosa cells begin secreting small amounts
of fluid. This follicular fluid , or liquor
folliculi , accumulates in small pockets that gradually expand and separate the
inner and outer layers of the follicle. At this stage, the complex is known as
a secondary follicle .
The Formation of a Tertiary
Follicle. Eight to 10 days after the start of the ovarian cycle, the ovaries
generally contain only a single secondary follicle destined for further
development. By the 10th to the 14th day of the cycle, that follicle has formed
a tertiary follicle , or mature Graafian follicle , roughly 15 mm in diameter. This
complex spans the entire width of the ovarian cortex and distorts the ovarian
capsule, creating a prominent bulge in the surface of the ovary. The oocyte
projects into the antrum , or expanded central
chamber of the follicle.
Instead of producing two secondary
oocytes, the first meiotic division yields a secondary oocyte and a small,
nonfunctional polar body. The secondary oocyte then enters meiosis II, but
stops once again on reaching metaphase. Meiosis II will not be completed unless
fertilization occurs.
Generally, on day 14 of a 28–day cycle, the secondary oocyte and the
surrounding granulosa cells lose their connections with the follicular wall.
The granulosa cells immediately surrounding the secondary oocyte now drift free
within the antrum and are known as the corona radiata.
Ovulation. At ovulation , the tertiary follicle releases the
secondary oocyte. The distended follicular wall ruptures, discharging the
follicular contents, including the secondary oocyte and corona radiata, into
the pelvic cavity.
The Formation and Degeneration of
the Corpus Luteum. The empty tertiary follicle initially collapses, and
ruptured vessels bleed into the antrum. The remaining granulosa cells then
invade the area, proliferating to create an endocrine structure known as the corpus luteum , named for its yellow color. This
process occurs under LH stimulation.
The lipids contained in the corpus
luteum are used to manufacture steroid hormones known as progestins principally the steroid progesterone. Although moderate amounts of estrogens
are also secreted by the corpus luteum, levels are not as high as they were at
ovulation, and progesterone is the principal hormone in the interval after
ovulation. Its primary function is to prepare the uterus for pregnancy by
stimulating the maturation of the uterine lining and the secretions of uterine
glands.
Unless Fertilization Occurs, the
Corpus Luteum Begins to Degenerate Roughly 12 Days After Ovulation.
Progesterone and estrogen levels then fall markedly. Fibroblasts invade the
nonfunctional corpus luteum, producing a knot of pale scar tissue called a corpus albicans. The disintegration, or involution ,
of the corpus luteum marks the end of the ovarian cycle. A new ovarian cycle
then begins with the activation of another group of primordial follicles.
Age and Oogenesis
At puberty, each ovary contains
about 200,000 primordial follicles. Forty years later, few if any follicles
remain, although only about 500 will have been ovulated during the interim.
A woman in the United
States has a 1 in 70 chance of developing ovarian cancer in her lifetime. In
2002, an estimated 23,300 ovarian cancers were diagnosed, and 13,900 women died
from this condition. Although ovarian cancer is the third most common
reproductive cancer among women, it is the most dangerous because it is seldom
diagnosed in its early stages. The prognosis is relatively good for cancers
that originate in the general ovarian tissues or from abnormal oocytes. These
cancers respond well to some combination of chemotherapy, radiation, and
surgery. However, 85 percent of ovarian cancers develop from epithelial cells,
and sustained remission can be obtained in only about one–third of the cases of
this type.
The Uterine Tubes ( Fallopian tube
or oviduct ) is a hollow, muscular tube measuring roughly 13 cm (5 in.) in
length. Each tube has 3 segments:
The Infundibulum. The
end closest to the ovary forms an expanded funnel, or infundibulum , with
numerous fingerlike projections that extend into the pelvic cavity. The
projections are called fimbriae. The inner surfaces of the infundibulum are
lined with cilia that beat toward the middle segment of the uterine tube,
called the ampulla .
The Ampulla. The
thickness of the smooth muscle layers in the wall of the middle segment, or
ampulla , of the uterine tube gradually increases as the tube approaches the
uterus.
The Isthmus. The ampulla
leads to the isthmus, a short segment connected to the uterine wall.
Pelvic inflammatory
disease (PID) in women is a major cause of sterility (infertility). An
infection of the uterine tubes, PID affects an estimated 850,000 women each
year in the United States. In many cases, sexually transmitted pathogens are
involved. As much as 50–80 percent of all first cases may be due to infection
by Neisseria gonorrhoeae , the organism responsible for symptoms of gonorrhea, a
sexually transmitted disease. Invasion of the region by bacteria that normally
reside in the vagina can also cause PID.
Recently, another
sexually transmitted bacterium, belonging to the genus Chlamydia , has been identified as
the probable cause of up to 50 percent of all cases of PID. Despite the fact
that women with this infection may develop few, if any, symptoms, scarring of
the uterine tubes can still produce infertility.
The Uterus provides mechanical
protection, nutritional support, and waste removal for the developing embryo
(weeks 1–8) and fetus (from week 9 to delivery). In addition, contractions in
the muscular wall of the uterus are important in ejecting the fetus at the time
of birth.
The uterus is a small, pear–shaped
organ about 7.5 cm (3 in.) long with a maximum diameter of 5 cm (2 in.). It
weighs 30–40 g (1–1.4 oz). In its normal position, the uterus bends anteriorly
near its base, a condition known as anteflexion. In this position, the uterus
tilts anteriorly, covering the superior and posterior surfaces of the urinary
bladder.
Suspensory Ligaments of the Uterus
In addition to the broad ligament, three pairs of suspensory ligaments
stabilize the position of the uterus and limit its range of movement.
Internal Anatomy of the Uterus
We can divide the uterus into two anatomical regions: the body and the cervix.
The uterine body , or corpus , is the largest
region of the uterus. The fundus is the
rounded portion of the body superior to the attachment of the uterine tubes.
The body ends at a constriction known as the uterine isthmus
. The cervix is the inferior portion of the uterus that
extends from the isthmus to the vagina.
The tubular cervix projects about
1.25 cm (0.5 in.) into the vagina. Within the vagina, the distal end of the
cervix forms a curving surface that surrounds the cervical
os ( os , an opening or mouth), or external orifice of the uterus. The
cervical os leads into the cervical canal , a
constricted passageway that opens into the uterine cavity
of the body at the internal os , or
internal orifice .
The arteries to the uterus are
extensively interconnected. This arrangement helps ensure a reliable flow of
blood to the organ despite changes in its position and the changes in uterine
shape that accompany pregnancy. Numerous veins and lymphatic vessels also
supply each portion of the uterus.
The Uterine Wall The wall has a thick, outer, muscular myometrium and a thin, inner, glandular endometrium, or mucosa .
The endometrium contributes about 10
percent to the mass of the uterus. The glandular and vascular tissues of the
endometrium support the physiological demands of the growing fetus. Vast
numbers of uterine glands open onto the endometrial surface and extend deep
into the lamina propria, almost to the myometrium. Under the influence of
estrogen, the uterine glands, blood vessels, and epithelium change with the
phases of the monthly uterine cycle .
The myometrium, the thickest portion
of the uterine wall, forms almost 90 percent of the mass of the uterus. Smooth
muscle in the myometrium is arranged into longitudinal, circular, and oblique
layers. The smooth muscle tissue of the myometrium provides much of the force
needed to move a large fetus out of the uterus and into the vagina.
Cervical cancer is the
most common cancer of the reproductive system in women age 15–34. Roughly
12,800 new cases of invasive cervical cancer are diagnosed each year in the
United States, and approximately 33 percent of the individuals will eventually
die of the condition. Another 34,900 patients are diagnosed with a less
aggressive form of cervical cancer.
The Uterine Cycle or menstrual cycle
, is a repeating series of changes in the structure of the endometrium. The
uterine cycle averages 28 days in length, but it can range from 21 to 35 days
in healthy women of reproductive age. We can divide the cycle into three
phases: (1) menses , (2) the proliferative phase , and (3) the secretory phase
.
The uterine cycle begins with the
onset of menses, an interval marked by the
degeneration of the functional zone of the endometrium. This degeneration
occurs in patches and is caused by the constriction of the spiral arteries,
which reduces blood flow to areas of endometrium.
Deprived of oxygen and nutrients, the
secretory glands and other tissues in the functional zone begin to deteriorate.
Eventually, the weakened arterial walls rupture, and blood pours into the
connective tissues of the functional zone. Blood cells and degenerating tissues
then break away and enter the uterine lumen, to be lost by passage through the
cervical os and into the vagina.
The sloughing off of tissue is
gradual, and at each site repairs begin almost at once. Nevertheless, before
menses has ended, the entire functional zone has been lost. The process of
endometrial sloughing, called menstruation,
generally lasts from one to seven days. Over this period roughly 35 to 50 ml of
blood is lost. The process can be relatively painless. Painful menstruation, or
dysmenorrhea , can result from uterine
inflammation and contraction or from conditions involving adjacent pelvic
structures.
The Proliferative Phase The basilar
zone, including the basal parts of the uterine glands, survives menses intact.
In the days after menses, the epithelial cells of these glands multiply and
spread across the endometrial surface, restoring the integrity of the uterine
epithelium. Further growth and vascularization result in the complete
restoration of the functional zone. As this reorganization proceeds, the endometrium
is in the proliferative phase . The
restoration occurs at the same time as the enlargement of primary and secondary
follicles in the ovary. The proliferative phase is stimulated and sustained by
estrogens secreted by the developing ovarian follicles.
The Secretory Phase During the secretory phase of the uterine cycle, the
endometrial glands enlarge, accelerating their rates of secretion, and the
arteries that supply the uterine wall elongate and spiral through the tissues
of the functional zone. This activity occurs under the combined stimulatory
effects of progestins and estrogens from the corpus luteum. The secretary phase
begins at the time of ovulation and persists as long as the corpus luteum
remains intact.
Secretory activities peak about 12 days after ovulation. Over the next day or
two, the glandular activity declines, and the uterine cycle comes to a close as
the corpus luteum stops producing stimulatory hormones. A new cycle then begins
with the onset of menses and the disintegration of the functional zone. The
secretory phase generally lasts 14 days. As a result, you can determine the
date of ovulation by counting backward 14 days from the first day of menses.
Menarche and Menopause The uterine
cycle begins at puberty. The first cycle, known as menarche,
typically occurs at age 11–12. The cycles continue until age 45–55, at menopause (MEN–o–pawz), the last uterine cycle. In
the interim, the regular appearance of uterine cycles is interrupted only by
circumstances such as illness, stress, starvation, or pregnancy.
If menarche does not appear by age
16, or if the normal uterine cycle of an adult woman becomes interrupted for
six months or more, the condition of amenorrhea
exists. Primary amenorrhea is the failure to initiate menses. This condition
may indicate developmental abnormalities, such as nonfunctional ovaries, the
absence of a uterus, or an endocrine or genetic disorder. It can also result
from malnutrition: Puberty is delayed if leptin levels are too low. Transient
secondary amenorrhea can be caused by severe physical or emotional stresses. In
effect, the reproductive system gets "switched off." Factors that
cause either type of amenorrhea include drastic weight loss, anorexia nervosa,
and severe depression or grief. Amenorrhea has also been observed in marathon
runners and other women engaged in training programs that require sustained
high levels of exertion and severely reduce body lipid reserves.
In endometriosis, an
area of endometrial tissue begins to grow outside the uterus. The cause is
unknown; because this condition is most common in the inferior portion of the
peritoneum, one possibility is that pieces of endometrium sloughed off during
menstruation are in some way forced through the uterine tubes into the peritoneal
cavity, where they reattach. Treatment
of endometriosis may involve hormonal therapy to suppress uterine cycles or
surgical removal of the endometrial mass. If the condition is widespread, a hysterectomy (removal of the
uterus) or oophorectomy (removal of the
ovaries) may be required.
The Vagina
The vagina is an elastic, muscular tube
extending between the cervix and the vestibule , a space bounded by the female
external genitalia.
It serves as a passageway for the
elimination of menstrual fluids.
It receives the penis during sexual
intercourse and holds spermatozoa prior to their passage into the uterus.
It forms the inferior portion of the
birth canal , through which the fetus passes during delivery.
The vagina and vestibule are
separated by the hymen, an elastic epithelial
fold that partially or completely blocks the entrance to the vagina before the
initial sexual intercourse. The two bulbospongiosus muscles extend along either
side of the vaginal entrance, which is constricted by their contractions. These
muscles cover the vestibular bulbs , masses of erectile tissue on either side
of the vaginal entrance. The vestibular bulbs have the same embryological
origins as the corpus spongiosum of the penis in males.
The vagina contains a population of
resident bacteria, usually harmless, supported by nutrients in the cervical
mucus. The metabolic activity of these bacteria creates an acidic environment,
which restricts the growth of many pathogens. Vaginitis, an inflammation of the
vaginal canal, is caused by fungi, bacteria, or parasites. In addition to any
discomfort that may result, the condition may affect the survival of
spermatozoa and thereby reduce fertility. An acidic environment also inhibits
the motility of sperm; for this reason, the buffers in semen are important to
successful fertilization.
The External Genitalia is the vulva, or pudendum. The paraurethral
glands , or Skene's glands , discharge into the urethra near the
external urethral opening. Anterior to this opening, the clitoris projects into the vestibule. A small,
rounded tissue projection, the clitoris is the female equivalent of the penis,
derived from the same embryonic structures. Internally, it contains erectile
tissue comparable to the corpora cavernosa of the penis. The clitoris engorges
with blood during sexual arousal. A small erectile glans sits atop it;
extensions of the labia minora encircle the body of the clitoris, forming its prepuce , or hood .
During sexual arousal, a pair of
ducts discharges the secretions of the greater
vestibular glands ( Bartholin's glands ) into the vestibule near the
posterolateral margins of the vaginal entrance. These mucous glands have the
same embryological origins as the bulbourethral glands of males.
The Mammary Glands are specialized organs
of the integumentary system that are controlled mainly by hormones of the
reproductive system and by the placenta , a temporary structure that provides
the embryo or fetus with nutrients.
The glandular tissue of the mammary
gland consists of separate lobes, each containing several secretory lobules.
Ducts leaving the lobules converge, giving rise to a single lactiferous duct in
each lobe. Near the nipple, that lactiferous duct enlarges, forming an expanded
chamber called a lactiferous sinus .
The inactive, or resting , mammary
gland is dominated by a duct system rather than by active glandular cells. The
size of the mammary glands in a nonpregnant woman reflects primarily the amount
of adipose tissue present, not the amount of glandular tissue. The secretory
apparatus does not complete its development unless pregnancy occurs. The active
mammary gland is a tubuloalveolar gland, consisting of multiple glandular tubes
that end in secretory alveoli.
Breast cancer is a
malignant, metastasizing cancer of the mammary gland. It is the leading cause
of death in women between the ages of 35 and 45, but it is most common in women
over age 50. Approximately 39,600 deaths will occur in the United States from
breast cancer in 2002, and approximately 203,500 new cases will be reported. An
estimated 12 percent of women in the United States will develop breast cancer
at some point in their lifetime, and the rate is steadily rising. The incidence
is highest among Caucasian–Americans, somewhat lower in African–Americans, and
lowest in Asian–Americans and American Indians. Notable risk factors include
(1) a family history of breast cancer, (2) a first pregnancy after age 30, and
(3) early menarche (first menstrual period) or late menopause (last menstrual
period). Breast cancers in males are very rare, but about 400 men die from the
disease each year in the United States.
Despite repeated
studies, no links have been proven between breast cancer and oral contraceptive
use, estrogen therapy, fat consumption, or alcohol use. It appears likely that
multiple factors are involved.
Hormones and the Female Reproductive
Cycle
hormonal control that involves an
interplay between secretions of both the pituitary gland and the gonads. But
the regulatory pattern in females is much more complicated than in males,
because it must coordinate the ovarian and uterine cycles. Circulating hormones
control the female reproductive cycle ,
coordinating the ovarian and uterine cycles to ensure proper reproductive
function. If the two cycles cannot be coordinated in a normal manner,
infertility results. A woman who fails to ovulate cannot conceive, even if her
uterus is perfectly normal. A woman who ovulates normally, but whose uterus is
not ready to support an embryo, will be just as infertile.
Hormones and the Follicular Phase
Follicular development begins under FSH stimulation; each month some of the
primordial follicles begin to develop into primary follicles. As the follicles
enlarge, thecal cells start producing androstenedione , a steroid hormone that
is a key intermediate in the synthesis of most sex hormones Androstenedione is
absorbed by the granulosa cells and converted to estrogens. In addition, small
quantities of estrogens are secreted by interstitial cells scattered throughout
the ovarian stroma. Circulating estrogens are bound primarily to albumins, with
lesser amounts carried by gonadal steroid–binding globulin (GBG).
Three estrogens circulate in the
bloodstream: (1) estradiol, (2) estrone, and (3) estriol. All have similar
effects on their target tissues. Estradiol is
the most abundant estrogen, and its effects on target tissues are most
pronounced. It is the dominant hormone prior to ovulation. In estradiol
synthesis, androstenedione is first converted to testosterone, which the enzyme
aromatase converts to estradiol. The synthesis of both estrone and estriol
proceeds directly from androstenedione.
Estrogens have multiple functions
that affect the activities of many tissues and organs throughout the body.
Among the important general functions of estrogens are (1) stimulating bone and
muscle growth, (2) maintaining female secondary sex characteristics, such as
body hair distribution and the location of adipose tissue deposits, (3)
affecting central nervous system (CNS) activity (especially in the
hypothalamus, where estrogens increase the sexual drive), (4) maintaining
functional accessory reproductive glands and organs, and (5) initiating the
repair and growth of the endometrium.
Hormones and the Luteal Phase
The high LH levels that trigger ovulation also promote progesterone secretion
and the formation of the corpus luteum.
Although moderate amounts of estrogens are secreted by the corpus
luteum, progesterone is the main hormone of the luteal phase. Its primary
function is to continue the preparation of the uterus for pregnancy by
enhancing the blood supply to the functional zone and stimulating the secretion
of the endometrial glands.
Progesterone levels remain high for
the next week, but unless pregnancy occurs, the corpus luteum begins to
degenerate. Roughly 12 days after ovulation, the corpus luteum becomes
nonfunctional, and progesterone and estrogen levels fall markedly. The blood
supply to the functional zone is restricted, and the endometrial tissues begin
to deteriorate. As progesterone and estrogen levels drop, the GnRH pulse
frequency increases, stimulating FSH secretion by the anterior lobe of the
pituitary gland, and the ovarian cycle begins again.
The hormonal changes involved with the ovarian cycle in turn affect the
activities of other reproductive tissues and organs. At the uterus, the
hormonal changes maintain the uterine cycle.
Hormones and the Uterine Cycle The
declines in progesterone and estrogen levels that accompany the degeneration of
the corpus luteum result in menses. The sloughing off of endometrial tissue
continues for several days, until rising estrogen levels stimulate the repair
and regeneration of the functional zone of the endometrium. The proliferative
phase continues until rising progesterone levels mark the arrival of the
secretory phase. The combination of estrogen and progesterone then causes the
enlargement of the endometrial glands and an increase in their secretory
activities.
Hormones and Body Temperature
The monthly hormonal fluctuations cause physiological changes that affect the
core body temperature. During the follicular phase, when estrogen is the
dominant hormone, the basal body temperature , or the resting body temperature
measured on awakening in the morning, is about 0.3 deg C lower than it is
during the luteal phase, when progesterone dominates. At the time of ovulation,
the basal body temperature declines noticeably, making the rise in temperature
over the next day even more noticeable. As a result, by keeping records of body
temperature over a few uterine cycles, a woman can often determine the precise
day of ovulation. This information can be important for individuals who wish to
avoid or promote a pregnancy, because fertilization typically occurs within a
day of ovulation. Thereafter, oocyte viability and the likelihood of successful
fertilization decrease markedly.
Birth Control
Strategies
Sterilization is a
surgical procedure that makes an individual unable to provide functional
gametes for fertilization. Either sexual partner may be sterilized. In a
vasectomy, a segment of the ductus deferens is removed, making it impossible
for spermatozoa to pass from the epididymis to the distal portions of the
reproductive tract. After a vasectomy, the man experiences normal sexual
function, because the secretions of the epididymis and testes normally account
for only about 5 percent of the volume of semen. Spermatozoa continue to
develop, but they remain within the epididymis until they degenerate. The
failure rate for this procedure is 0.08 percent.
The uterine tubes can be
blocked by a surgical procedure known as a tubal ligation. The failure rate for
this procedure is estimated at 0.45 percent. Because the surgery requires that
the abdominopelvic cavity be opened, complications are more likely than with
vasectomy.
Oral contraceptives
manipulate the female hormonal cycle so that ovulation does not occur. The
contraceptive pills produced in the 1950s contained relatively large amounts of
estrogen and progestins. These concentrations were adequate to suppress
pituitary production of GnRH, so FSH was not released and ovulation did not
occur. In most of the oral contraceptive products developed subsequently,
smaller amounts of estrogens have been used. Current combination pills differ
significantly from the earlier products in that the hormonal doses are much
lower, with only one–tenth the progestins and less than half the estrogens.
The failure rate for the
combination oral contraceptives, when used as prescribed, is 0.24 percent over
a two–year period. Birth control pills are not risk free: Combination pills can
worsen problems associated with severe hypertension, diabetes mellitus,
epilepsy, gallbladder disease, heart trouble, and acne. Women taking oral
contraceptives are also at increased risk of venous thrombosis, strokes,
pulmonary embolism, and (for women over 35) heart disease.
Three progesterone–only
forms of birth control are now available: the system, and the progesterone–only
pill. Depo–provera is injected every 3 months. Uterine cycles are initially irregular, and
in roughly 50 percent of women using this product they eventually cease. The
major problems with this contraceptive method are (1) a tendency to gain weight
after three or more years of using it and (2) a slow return to fertility (up to
18 months) after injections are discontinued. The (silicone rubber) tubes of
the Norplant system are saturated with
progesterone and inserted under the skin. This method provides birth control
for approximately five years, but to date the relatively high cost has limited
its use. Because it does not supply estrogen, it produces fewer hormonal side
effects than combination pills do. Fertility returns immediately after the
removal of a Norplant device. Both Depo–provera and the Norplant system are
easy to use and are extremely convenient. The progesterone–only pill is taken
daily and may cause irregular uterine cycles. Skipping just one pill may result
in pregnancy.
Although pregnancy is a
natural phenomenon, it has risks, and the mortality rate for pregnant women in
the United States averages about 8 deaths per 100,000 pregnancies. That average
incorporates a broad range: The rate is 5.4 per 100,000 women under 20, but 27
per 100,000 among women over 40. Although these risks are small, for pregnant
women over age 35 the chances of dying from complications related to pregnancy
are almost twice as great as the chances of being killed in an automobile accident
and are many times greater than the risks associated with the use of oral
contraceptives. For women in developing nations, the comparison is even more
striking: The mortality rate for pregnant women in parts of Africa is
approximately 1 per 150 pregnancies. In addition to preventing pregnancy,
combination birth control pills have been shown to reduce the risks of ovarian
and endometrial cancers and fibrocystic breast disease.
Menopause typically occurs at age
45–55, but in the years preceding it, the ovarian and uterine cycles become
irregular. Menopause is accompanied by a
decline in circulating concentrations of estrogen and progesterone and a sharp
and sustained rise in the production of GnRH, FSH, and LH. The decline in
estrogen levels leads to reductions in the size of the uterus and breasts,
accompanied by a thinning of the urethral and vaginal epithelia. The majority
of women experience only mild symptoms, but some individuals experience acutely
unpleasant symptoms in perimenopause or during or after menopause. For most of
those individuals, hormone replacement therapies involving a combination of
estrogens and progestins can prevent osteoporosis and the neural and vascular
changes associated with menopause. The hormones are administered as pills, by
injection, or by transdermal "estrogen patches." The synthetic
hormone etidronate inhibits osteoporosis by suppressing osteoclast activity.
The Male Climacteric Changes in the
male reproductive system occur more gradually than do those in the female
reproductive system. The period of change is known as the male climacteric . Levels of circulating
testosterone begin to decline between the ages of 50 and 60, and levels of
circulating FSH and LH increase. Although sperm production continues (men well into
their eighties can father children), older men exper
