Female reproductive systems
Female reproductive systems
consist of the following
1) External genitalia
2) A pair of primary sex
glands (gonads)
3) Ducts leading from the
gonads to the body’s exterior
4) secondary sex glands.
In the normal course of
events, life begins and is sustained for 9 months within the productive
environment of the female. Therefore the female organs will
be considered first, beginning with the external
genital structures.
The female’s external
and internal reproductive structure are targets for estrogen’s
throughout her life span and they atrophy (reduce in size) with age and /or a
drop in estrogen production. An
extensive and complex innervation and very generous blood supply support the
functions of these structures. The
comparative size, woman depending on her heredity, age, race and number of
children she has borne.
External Structures
Following are the external female genitalia
(vulva, pudenda).
1)
Mons veneris (mons pubis)
2)
Labia majora and minora
3)
Clitoris
4)
Vestibule
¨1
Urinary meatus, or urethral orifice
¨2
Lesser vestibular, paraurethral, or Skene’s glands
¨3
Hymen and vaginal introitus, or orifice
¨4
Greater vestibular, vulvovaginal, or Bartholin’s glands
1)
Fourchet
2)
Perineum
The mons veneris or mons pubis, is the
rounded, soft fullness of subcutaneous fatty tissue and loose connective tissue
over the symphysis pubis. It contains many sebaceous (oil) glands and develops
coarse, dark, curly hair at pubarche, about 1 to 2 years before the onset of
the menses.
Typically, the pattern of
hair growth in 75% of women is a triangle shape with the base along the top of
the symphysis pubis. In 25% of women, pubic hair extends upward the umbilicus
along the linea alba. The function of the mons are to play a role in sensuality
and to protect the symphysis pubis during coitus.
Labia majora are two rounded lengthwise
folds of skin-covered fat and connective tissue that merge with the mons. They
extend from the mons downward around the labia minora, ending in the perineum
in the midline, and act as protection for the labia minora, urinary meatus, and
vaginal introitus.
On their lateral surfaces, the
labial skin is thick, usually pigmented darker than the
surrounding tissue, and covered with coarse hair that thins out
toward the perineum. The medial (inner) surfaces of the labia
majora are smooth, thick, and without hair. They contain an abundant
supply of sebaceous glands and sweet glands and are highly
vascular.
The lymphatic system
is extensive and serves many structures in the pelvic area. This is the reason
for the extensive and rapid spread of reproductive tract malignancies.
The extreme sensitivity of
the labia majora to touch, pain and temperature is due to the extensive network
of nerves. Innervation of the anterior one third of the labia is from L1
(lumber 1), while the posterior two thirds is supplied mainly from S3 (sacral
3)
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The pair of round
ligaments from the uterus inserts into the anterior portion of the labia
majora.
The clitoris is a short, cylindric,
erectile organ liked just beneath the arch of the pubis; the visible portion is
about 6 X 6 mm.
Its rich vascularity and
innervation make the clitoris highly sensitive to temperature, touch, and
pressure sensation.
The vestibule
is an ovoid or boat-shaped area formed between the labia minora, clitoris,
and fourchet. The vestibule
contains the openings to the urethra, paraurethral (lesser vestibule, Skene’s )
glands, the vagina, (greater vestibular or Bartholin’s) glands.
The humen is a
partial, rarely complete, elastic but mucosa-covered fold around the
vaginal introitus
The greater
vestibular (Bartholin’s) glands are two compound glands
at the base of the labia majora, one on either side of the vaginal orifice.
Each gland is drained by several ducts, about 1.5 cm long. Each opens into the
groove between the hymen and the labia minora. Usually the gland openings are
not visible or palpable. The glands secrete a small amount of clear, viscid
mucus, especially during coitus. The alkaline pH of the mucus is supportive of
sperm. These glands are susceptible to gonorrheal infection and to abscess and
cyst formation.
The fourchet
is a thin, flat, transverse fold of tissue formed where the tapering labia
majora and minora merge in the midline below the vaginal orifice.
The perineum
is the skin-covered muscular area between the vaginal introitus and the
anus. The perineum forms the base of the perineal body.
Pelvic floor and perineum. The pelvic and perineum
are composed of the pelvic diaphragm, the urogenital diaphragm or triangle, and
the muscle of the external genitalia and anus
The upper pelvic
diaphragm ,composed of muscles and their fascia and ligaments, extends
across the lowest part of the pelvic cavity. The largest anus most significant
portion of the diaphragm is formed by the pair of broad, thin levator ani
muscles that extend sheetlike between the ischial spines and coccyx, and
the sacrum. The levator ani group of muscle is made up of three
muscle pairs:
·
puborectalis,
·
iliococcygeus, and
·
pubococcygeus muscles.
The pubococcygeus muscle
is particularly significant for women. Its importance lies on bladder
control and during labor for controlling perineal relaxation
and expulsion of the fetus during birth.
The second paired muscles
of the upper pelvic diaphragm are the closely joint coccygeus muscles
These muscles extend from the
ischial spines to the coccyx and lower sacrum.
The urogenital (lower
pelvic) is located in the hollow of the pubic arch and consists of the transverse
perineal muscles. The transverse
perineal muscles originate at the ischial tuberosities and insert
into the perineal body. The strong muscle fibers provide support to
the anal canal during defecation and to the lower vagina during delivery.
The deep transverse perineal muscles join to form a central seam or raphe.
Some of their fibers encircle the urinary meatus and vaginal sphincters.
The perineum
is located below the upper and lower pelvic diaphragm. Its muscles and fascia
reinforce the strength of the pelvic diaphragm and aid in constricting the
urinary, vaginal, and anal openings. The bulbocavernosus muscle
fibers originate in the perineal body and surround the vaginal openings as the
muscle fibers pass forward to insert into the pubis.
The ischiocavernous
muscle originate in the tuberosities of the ischium and continue
at an angle to insert next to the bulbocavernosus muscle. These muscle fibers
contract to cause erection of the clitoris.
Anal sphincter muscle
fibers originate
at the coccyx, separate to pass on either side of the anus, fuse, and then
insert into the transverse perineal muscles.
The bulbocavernosus,
transverse perineal, and anal sphincter muscle fibers can
be strengthened through Kegel exercises.
The perineal body, the wedge-shaped mass
between the vaginal and anal openings, serves as an anchor point for the
muscle, fascia, and ligaments of the upper and lower pelvic diaphragm The
skin-covered base of the body is known as the perineum. The perineal body,
about 4 cm wide by 4 cm deep, is continuous with the septum between the rectum
and vagina.
Knowledge of the anatomy
and physiology of the pelvic floor and perineum provides a basis for
understanding and implementing appropriate nursing actions in
relations to voluntray sphincter control during urination, coitus, and
defecation and the normal mechanism of labor and delivery. In addition, the
student has the information necessary to understand and utilize knowledge
regarding the etiology, management, and prevention of disorders such as uterine
prolapse and urinary stress incontinence.
Internal Genitalia
Vagina
Location and support. The vagina is a tubular
structure located in front of the rectum and behind the bladder and urethra.
The vagina extends from the interoitus, the external opening in the vestibule
between the labia minora of the vulva, to the cervix. It is supported mainly by
its attachment to the pelvic floor musculature and fascia.
Structure. The vagina
is a thin-walled, collapsible tube that is capable of great distention. Because
of the way the cervix protrudes into the uppermost portion of the vagina, the
length of the anterior wall of the vagina is only about 7 to 8 cm while that of
the posterior wall is about 10 cm. The recesses formed all around the
protruding cervix are called fornices: right, left, anterior, and posterior.
The posterior fornix is deeper than the other three.
The smooth muscle walls
are lined with glandular mucosa is arranged in transverse folds called rugae.
Innervation. The vagina is
relatively insensitive. There is some innervation from the pudendal and
hemorrhoidal nerves to the lowest one third. The nerve supply is mainly
autonomic. Sensations arising in the vagina terminate at the level of S2, S3,
and S4.
Blood supply. The copious blood supply to
the vagina is derived from the descending branches of the uterine artery, the
middle hemorrhoidal artery, and the internal pudendal arteries. The venous
return of the vaginal blood is through the pudendal, external hemorrhoidal, and
uterine veins.
Lymphatics. The lymphatics of the
upper vagina drain to the rectovaginal septal, presacral, external iliac, and
hypogastric nods. The lower vaginal lymphatic are directed to the superficial
inguinal nodes.
Uterus
The uterus is a hollow
viscus composed of plain muscle whose sole function is gestation. It lies between the rectum and the
bladder and is continuous with the vagina.
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Structure
Shape, size, and divisions. The uterus is a fattened,
hollow, muscular, thick-walled organ that looks somewhat like an upside-down
pear. Its length, width, and thickness vary, averaging about 7.5 cm x 3.5 cm x
2cm (3 x 11/2 x 3/4 in). In adult woman who has never been pregnant, the uterus
weighs 60 g (2 oz).
The uterus has three parts
:the fundus, the upper, rounded prominence above the insertion of the
fallopian tubes; the corpus, or main portion, encircling the
intra-uterine cavity; and the isthmus, the slightly constricted portion
that joins the corpus to the cervix and is known as the lower uterine segment
during pregnancy.
Uterine wall. The wall of the uterus is
made up of three layers: the endometrium, the myometrium, and a partial outer
layer of parietal peritoneum.
Cervix The lowermost portion of
the uterus is the cervix, or neck
The attachment site of the uterine cervix to the vaginal vault divides
the cervix into the longer superavaginal (above the vagina) portion and the
shorter vaginal portion. The length of the cervix is about 2.5 to 3.0 cm, of
which about 1 cm protrudes into the vagina in the nongravid woman.
The external os is small
before parturition. After the birth of a child it becomes a transverse slit
‘the parous os’
Uterine position. For the majority of
normal women, with the urinary bladder empty, the uterus is anteverted and
slightly anteflexed. The cervix is directed downward and backward the tip of
the sacrum so that it is usually at approximately a right angle to the plane of
the vagina. For other women the uterus may be in the middle position or tipped
backward (retroverted)
A full bladder pushes
the uterus back toward the rectum, while a full rectum moves the uterus
forward against the bladder. Uterine position also changes depending on the
woman’s position (e.g., lying supine, prone, on her side, or standing), her
age, and pregnancy.
Uterine support. The uterus is supported by ligaments and by muscles of the
pelvic floor, including the perineal body. A total of 10 ligaments stabilize
the uterus within the pelvic cavity : four paired ligaments (broad, round,
uterosacral, and cardinal) and two single ligaments (anterior and posterior).
The paired broad
ligaments are double folds of parietal peritoneum that extend
wing-like from the sides of the uterus to the pelvic walls. These ligaments
divide the pelvic cavity into anterior and posterior components. In the upper
portion of the broad ligaments are suspended the fallopian tubes, ovaries,
round ligaments, and ovarian ligaments.
The two round ligaments
extend from the upper outer angles formed where the fallopian tubes join the
uterine corpus (at the cornua), through the inguinal canals, and ending in the
labia majora.
The single anterior (uterovesical
or pubocervical) ligament is a continuation of parietal peritoneum that
forms the anterior fold of the broad ligament, extending from the anterior surface
of the supravaginal cervix of the uterus to the posterior surfac4e of the
bladder. The pouch formed by the fold of peritoneum is less deep than that the
posterior pouch.
The denser connective
tissue of the lower portion of the broad ligaments is sometimes known as the cardinal,
transverse, or Mackenrodt’s The cardinal ligaments form the
upper portion of the posterior ligament.
The single posterior
(or rectovaginal ) ligament is a continuation of parietal peritoneum (posterior
fold of broad ligament) extending from the posterior surface of the uterus to
the rectum. The posterior ligament forms the deep rectouterine pouch also known
as the cul-de sac of Douglas
This pouch is the
lowest part of the abdominal cavity so that blood, pus, or other drainage
collects here. The pouch can be reached through the posterior vaginal fornix.
The two uterosacral
ligaments are cord like folds of peritoneum extending from the
supravaginal cervical portion of the uterus to the fascia over the second and
third sacral vertebrae passing on each side of the rectum. These ligaments hold
the uterus in position by maintaining traction on the cervix.
In summary the main uterine
support are the ligaments surrounding the supravaginal cervix:
1)
Anterior (pubocervical)
2)
Cardinal (transverse, Mackenrodt’s)
3)
Posterior (rectovaginal)
4)
Uterosacral
Uterine lymphatics. The lymphatics of the
uterus are extensive. They are contained in three networks: at the base of the
endometrium, within the myometrium, and just under the peritoneal coat of the
uterus. Lymphatic drainage occurs mainly at the isthmus along the uterine
vessels.
Uterine blood supply. The abdominal aorta
divides at about the level of the umbilicus and forms the two iliac arteries.
Each iliac artery divides to forms the two iliac arteries, the major one of
which is the hypogastric artery. The uterine arteries branch off from the hypogastric
arteries.
In the nonpregnant state
the uterine blood vessels are coiled and tortuous. With advancing pregnancy and
an enlarging uterus, these blood vessels straighten out. The uterine veins
follow along the arteries and empty into the internal iliac veins.
Innervation of the uterus. The internal genitalia
have a rich supply of afferent and efferent autonomic nerves both motor and
sensory.
Motor nerves. Parasympathetic fibers
from the sacral nerves are probably responsible for producing vasodilatation
and inhibiting muscular contraction. Efferent sympathetic motor nerves arise
from the ganglia of T5 (thoracic5) to T10, come together over the sacrum, and
reach the uterus through ganglia that lie near the base of the uterosacral
ligaments. The autonomic nerves just described (parasympathetic fibers and
efferent sympathetic motor) regulate the action of the uterus, but the uterus
has an intrinsic motility (i.e., it can contract and relax even if the nerves
to it are cut).
Sensory nerves. Sensory fibers carrying
pain sensation from the uterus, come together in the paracervical areas and
proceed upward to pass just below the division (bifurcation of the aorta, and
then travel into the spinal cord at the level of T11 and T12. Because of this
arrangement, pain that originate in the ovary or in the ureters may mimic pain
that originate in the uterus, any of which may be felt in the flank and down to
the inguinal and vulvar areas.
Functions. The three functions of the
uterus are essential for the survival of the species but not for the
individual: cyclic menstruation with rejuvenation of the endometrium,
pregnancy, and labour.
Fallopian tubes. The paired
Fallopain (uterine) tubes measure about 12 cm in length. Each tube has an outer coat of
peritoneum, a middle thin muscular coat, and an inner mucosa. The smooth muscle fibers are arranged
in an inner circular and an outer longitudinal layer. The mucosal lining
consists of columnar cells some of which are ciliated and others of which are
secretory.
The structure of the
fallopian tube changes along its length.
Four distinctive segments
can be identified:
1.
the infundibulum,
2.
the ampulla,
3.
the isthmus, and
4.
the interstitial part.
The infundibulum,
is the most distal portion. Its funnel-shaped opening is encircled with
fimbria. The fimbria become swollen, almost erectile, at ovulation. It is 2cm
long. The function of these fingerlike projections is to pull the ovum into the
tube.
The ampulla
makes up the distal and middle segment of the tube. It is in the ampulla that
the sperm and ovum meet, where ferilization occurs. 5cm long, thin walled and
convoluted.
The isthmus
is proximal to the ampulla. It is 2 cm long, straight and cord-like 1mm
diameter.
The interstitial
portion passes through the myometrium between the fundus and the body
of the uterus and 1cm long and very narrow (less than 1mm).
Ovaries: female gonades
Location and support. One ovary is
located on each side of the uterus, below and behind the uterine tubes. The ovaries
are held in place by two ligaments, the mesovarian portions of the uterine
broad ligament, which suspend them from the lateral pelvic side walls at about
the level of the anterosuperior iliac crest, and the ovarian ligaments, which
anchor them to the uterus. The ovaries are movable with palpation.
Structure. Each ovary is composed of
two layers around a central zone. Each is whitish and rounded but flattened
weights about 3 g, and measures approximately 3 x 2 x 1 cm. At the time of
ovulation, ovarian size may double temporarily.
Blood supply and
lymphatics. Ovarian arteries carry a rich blood supply from the aorta to the
ovaries. The left ovarian vein empties into the left renal vein, but the right
drains into the inferior vena cava. The ovarian lymphatics drain into the iliac
and periaortic nodes.
Innervation. The nerve supply to the
ovary is through T10 to L1, together with fibers of the pelvic sympathetic
nervous system.
Functions. The two functions of the
ovary are ovulation and hormone production.
Anatomy of the bony pelvis. During birth, the fetus
must pass through the bony passage formed by the pelvis
The pelvis is a bony
ring that is supported by the lower extremities and that in turn the weight
of the trunk and upper body.
The pelvis is made up of
the following four bones: the right and left innominate bones, each of which is
made up of the right or left pubic bone, ilium, and ischium,
which fuse after puberty; the sacrum , and the coccyx.
The two innominate bones
(hip bones) form the sides and front of the bony passage, and the sacrum and
coccyx form the back.
Below the ilium is
the ischium, a heavy bone terminating posteriorly in the rounded
protuberances known as the ischial tuberosities. The tuberosities bear
the body’s weight in the sitting position.
The sharp projections,
the ischial spines, project from the posterior border of the ischium
into the pelvic cavity. The spines, which may be blunt or prominent, have
obstetric importance for two reasons:
1)
The distance between the
two ischial spines is the narrowest diameter of the pelvic cavity.
2)
They serve as the landmark
to determine the degree of descent of the fetus during labor.
The pubis, forming
the front portion of the pelvic cavity, is located beneath the mons. In the
midline, the two pubic bones are joined by strong ligaments and a thick
cartilage to form the joint called the symphysis pubis. The descending rami
(ramus [sing.] branch or arm) form the subpubic arch. In the female, the angle
formed by the arch optimally measure slightly more than 90 degrees.
The sacrum is formed
by five fused vertebrae. The upper anterior portion of the body of the first
sacral vertebra, the promontory, forms the posterior margin of the pelvic brim.
The
contents of the peritoneum
(culdocentesis).
Following the examination,
the physician, using diagrams or pictures as indicated, should discuss the
findings with the patient so that she understands her condition and the
alternatives of therapy.
Menstrual Cycle
Menstrual Myths
An awareness of some myths
about menstruation and their cultural origins is necessary to use the nursing
process effectively with both female and male clients.
The belief systems held by
researchers may also influence the research methodology used and the way
results are interpreted, presented in the literature, and used by society in
general (i.e., people tend to color things the way they want to see them).
Many myths have
their origin in the mystery that surrounded the woman, her hidden reproductive
organs, and her uniqueness in adding new members to society. Before the
eighteenth century, the relationship of the menstrual cycle to reproduction was
obscure.
Menstrual flow was believed to be the
elimination of poisons that had accumulated in the woman. The discovery of the
fallopian tubes did nothing to clear up this misconception.
Because of their recurring
nature, menstrual cycles were thought to be under the control of the moon.
Before the discovery of ovulation in humans, it was thought that an egg was
produced during menstruation only when fruitful intercourse had occurred. Not
until the nineteenth century was knowledge available about the existence of the
human egg, ovulation and ovarian functioning.
The most common myths
in existence today can be sorted out under the following headings:
1.
During menstruation, the woman is vulnerable and therefore needs to be
protected.
2.
The menstruating woman can pose a danger.
3.
Menstrual blood has been
viewed as possessing healing powers. Or of some black magic power
The menstruating woman
is seen as being vulnerable to physical and psychological stress. Recall some
of myths you may have heard; for example, “Don’t wash your hair,” “Don’t take a
bath,” “Watch out, you’ll catch cold,” “That’s too heavy for you to you to
carry now ,”
Historical Perspective
During this century there
have been significant additions to the knowledge of the biophysical and
emotional aspects of the menstrual cycle. Since then, pituitary hormones have
been purified and hypothalamic control over the pituitary gland has been studied
extensively.
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Hypothalamus and Pituitary
Neurons from several
portions of the brain terminate in the hypothalamus. The cell bodies of the
secretory neurons are located within the median eminence (middle portion) of
the hypothalamus while the nerve endings lie close to capillary loops slightly
above the pituitary portal (circulatory) system. Thus the circulation picks up
the hypothalamic neurohormones and carries them to the anterior pituitary,
which normally responds to each specific releasing or inhibiting neurohormone
“command.”
One releasing hormone,
gonadotropin-releasing hormone (GnRH) causes the synthesis and release of
both follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
from the anterior pituitary glands. Emotional stress communicated to the
hypothalamus can depress the formation and release of GnRH, preventing
the release of FSH and LH. As a result, ovulation does not occur,
progesterone is not produced, and amenorrhea results
Central Nervous System
Normal events and stimuli
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Hypothalamus |
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GnRH |
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(anterior pituitary) |
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FSH |
LH |
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Graafian
follicle |
Graafian
follicle |
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Estrogen prepare
endometrium |
Corpus
luteum |
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Ovulation |
Progesterone (some
estrogen) |
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prepare
endometrium |
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Menstruation |
Follicle-stimulating
Hormone (FSH)
Female Ovary
Growth and maturation of
graafian follicles and preparation of these cells so that they can respond to
LH
luteinizing Hormone (LH)
Female Ovary
Works with FSH to stimulate
estrogen secretion. Along with a surge of LH, estrogen stimulates ovulation,
then luteinizes the follicle to form the corpus luteum produces progesterone
and estrogen.
Hypothalamic-Pituitary
Cycle
Toward the end of the
normal menstrual cycle, blood levels of estrogen and progesterone fall.
Low blood level of these ovarian hormones stimulate the hypothalamus
to secrete GnRH, which in turn stimulates anterior pituitary
secretion of FSH. FSH stimulates development of ovarian
graafian follicles and their production of estrogen. Estrogen levels
begin to fall and hypothalamic GnRH triggers the anterior pituitary
release of LH. A marked surge of LH and smaller peak of
estrogen precede the expulsion of the ovum from the graafian follicle by about
24 to 36 hours.
Ovarian Cycle
The primary graafian
follicles contain immature oocytes. Before ovulation, from 1 to 30
follicles begin to mature in each ovary under the influence of
FSH and estrogen. The preovulatory surge of LH affects a selected
follicle. Within the chosen follicle, the oocyte matures, ovulation
occurs, and the empty follicle begins its transformation into the
corpus luteum (yellow body).
This follicular phase (preovulatory
phase) of the ovarian menstrual cycle varies in length from woman to woman. Almost
all variations in cycle length are the result of variations in the length of
the follicular phase. On rare occasions (1 in 100 menstrual cycles),
more than one follicle is chosen and more than one oocyte mature and
undergoes ovulation (twins).
The events following ovulation,
the luteal phase (postovulatory phase) of the ovarian
menstrual cycle, usually require 14 days (range of 13 to 15 days). Eight
days after ovulation, the corpus luteum reaches its peak of functional
activity, secreting both of the steroids, estrogen and progesterone.
Coincident with this time of peak luteal functioning, the fertilized egg is
implanted in the endometrium. If no implantation occurs, the corpus
luteum regresses, and steroid levels drop. Two weeks after
ovulation, if fertilization and implantation do not occur, uterine endometrium
is shed through menstruation.
After ovulation, estrogen
levels drop. For 90% of women, only a small amount of withdrawal bleeding occurs so that is goes unnoticed. In 10%
of women, there is sufficient bleeding for it to be visible, resulting in what
is known as midcycle bleeding
Endometrial Cycle
The endometrium
responds to fluctuating levels of ovarian steroids. The endometrium consists of
three layers. The basal layer intermingles with the myometrium. The other two
functional layers undergo cyclic changes and are shed in menstrual flow.
When labeled according to
phases in the endometrial cycle, the menstrual phase extends over
the first 5 days when the two functional layers (the compact and
spongy layers) are shed. The resting, or repair, phase ( the early
proliferative phase) includes days 4 through 7.
The most rapid growth of
the functional layers occurs between days 5 to 7 and the day of ovulation and
is known as the proliferative phase. In a 28-day cycle, ovulation occurs
on day 14 (range of 13 to 15 days). The secretory phase spans days 15 through
28; the last 3 days before menstruation make up the ischemic phase (stage of
regression).
The endometrium has
different characteristics at different times during the cycle depending on the
levels of estrogen and progesterone. Therefore the endometrium can be “dated”
(the phase of the cycle can be determined) and the presence and levels
of hormones are too low or too high, the endometrium would reflect this.
The first day of
menstrual discharge has been designated as day 1 of the cycle. The average
duration of menstrual flow is 5 days (range of 3 to 6 days), and
the average blood loss is approximately 50 ml (range of 20 to 80
ml), but there is great variation. During menstruation, the average daily loss
of iron is 0.5 to 1mg. If the woman’s usual blood loss is over 80 ml,
she will most likely need iron supplementation to prevent secondary anemia.
Uterine discharge includes mucus
and epithelial cells in addition to blood.
Ovulation occurs about 14 days
before the start of the next menstrual flow, for example, day 10 of a 24-day
cycle, day 14 of a 28-day cycle, or day 18 of a 32-day cycle.
The endometrium
surface is completely restored in approximately 4 days or slightly
before the menstrual flow stops. From this point on, an eight fold to tenfold
thickening occurs, with a leveling off of growth at ovulation. During the
proliferative phase, the glands are tubular or columnar in shape. About 3 to 4
days before ovulation, vascularity to the endometrium increases. Endometrial
growth during proliferation is dependent on estrogen produced by ovarian
follicles before ovulation.
After ovulation, the
graafian follicle develops into the corpus luteum. The corpus
luteum produces estrogen and large amounts of progesterone. Progesterone causes
the blood vessels in the endometrium to dilate and assume a spiral or corkscrew
shape. Endometrium glands elongate, become more active, and secrete a glycogen
containing fluid. The endometrium reaches the thickness of heavy, soft velvet
and becomes luxuriant with blood and glandular secretions, a suitable
protective and nutritive bed for a fertilized ovum. In the fully matured
secretory endometrium, three strata are noted: the two functional or
compact layer and an intermediate or spongy layer; and basal or inner, inactive
layer.
If fertilization
does not occur, about 3 days before menstruation begins, the corpus luteum
degenerates with
Vasospasm of the spiral arteries occurs. This
vasoconstriction results in ischemia, necrosis, and sloughing off of the upper
two layers of the endometrium. Near the end of the secretory phase, just before
the start of menstrual flow, regeneration begins from the retained basal layer.
Rebuilding the endometrium from the basal layer upward is responsible for
its healing and rejuvenation without scar formation.
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