Download Female Reproductive System

FEMALE REPRODUCTIVE SYSTEM
The organs of the female reproductive system include the ovaries, which produce
secondary oocytes and hormones, such as progesterone and estrogens (the female sex
hormones), inhibin and relaxin; the uterine (fallopian) tubes, or oviducts, which transport secondary
oocytes and fertilized ova to the uterus, in which embryonic and fetal development occur; the
vagina; and the external organs that constitute the vulva, or pudendum. The mammary glands also
are considered part of the female reproductive system.
OVARIES:
The ovaries are the female reproductive organ in which sex cells (eggs, or ova) are
produced. The usually paired ovaries of female vertebrates produce both the sex cells and the
hormones necessary for reproduction. Female gonads that equate to the testes in the male are
the ovaries. The ovaries are paired glands that are small and almond shaped. There is one on
either side of the uterus, and during the third month of development they descend to the edge of
the superior part of the pelvic cavity.
The primary function of the ovaries is to nurture and prepare oocytes (eggs) for the
process of ovulation (rupture and release of the mature egg from the ovary). Once an egg is
released, it migrates down a fallopian tube to the uterus. While in the fallopian tube, an egg may
be penetrated and fertilized by a sperm. If an egg becomes fertilized, it will implant in the wall of
the uterus. The processes of ovulation and fertilization are controlled largely by cells in the
ovaries that produce and secrete hormones. These hormones also are essential for female sexual
development and are necessary to sustain a pregnancy. In humans they also serve to regulate the
menstrual cycle (periodic shedding of the uterine lining).
The broad ligament in the uterus is attached to the ovaries by a fold of peritoneum called
the mesovarium. The ovaries are attached to the uterus by the ovarian ligament and the
suspensory ligament attaches them to the pelvic wall. The blood vessels and nerves enter and
exit the ovaries through an area called the hilum.
An ovary is subdivided into cortical (ovarian cortex) and medullary compartments
(ovarian medulla). Both blood and lymph vessels are found in the loose connective tissue of the
ovarian medulla. In the cortical compartment the oocytes are present within the various follicle
stages.
The sex hormones influence the primordial follicles to grow and a restructuring to take
place. From the primordial follicles the primary follicles, secondary follicles, and tertiary follicles
develop in turn. Only a small percentage of the primordial follicles reach the tertiary follicle stage the great majority meet their end beforehand in the various maturation stages. Large follicles leave
scars behind in the cortical compartment and the small ones disappear without a trace.
The tertiary follicles get to be the largest and, shortly before ovulation, can attain a
diameter up to 2.5 mm through a special spurt of growth. They are then termed graafian follicles.
As a woman ages, the follicles gradually diminish in number until, at menopause and the
cessation of reproductive function, the few remaining follicles degenerate.
HISTOLOGY OF OVARIES: (found in each ovary)
Germinal epithelium: layer of simple epithelium that covers the surface of the ovary. It is
continuous with the mesothelium.
Tunica albuginea: immediately deep to the germinal epithelium is a capsule of dense connective
tissue that appears white
Ovarian cortex: contains ovarian follicles surrounded by dense irregular connective tissue. Just
deep to the tunica albuginea.
Ovarian medulla: deep to the ovarian cortex containing loosely arranged connective tissue, blood
vessels, lymphatic vessels and nerves.
Ovarian follicles: contains oocytes and cells surrounding them. They are located in the ovarian
cortex of the ovary. When the surrounding cells form a single layer they are called follicular cells,
however, during development when they form multiple layers they are called granulosa cells.
During development, the surrounding cells nourish the developing oocyte and secrete estrogens as
the cell grows larger.
Mature graafian follicle: major part of ovulation. It is a large fluid-filled follicle that is ready to
rupture and expel its secondary oocyte.
Corpus luteum: produces progesterone, estrogens, relaxin and inhibin as well as holds the
remnants of a mature follicle after ovulation. It turns into fibrous scar tissue called the corpus
albicans as it degenerates.
The ovaries receive their blood from the ovarian arteries and drain their blood through ovarian
veins. On the right side they drain into the inferior vena cava and on the left side they drain into the
renal vein.
OOGENESIS AND FOLLICULAR DEVELOPMENT:
Oogenesis begins in females before they are even born. It is the process of forming
gametes in the ovaries. It occurs using meiosis and the resulting germ cells undergo maturation.
During early fetal development, cells call the primordial germ cells migrate from the yolk sac to the
ovaries. In the ovaries, the germ cells differentiate into oogonia. Oogonia are diploid (2n) stem
cells that mitotically divide to produce millions of germ cells. While the oogonia transform into
primary oocytes, they become restructured so that at the end of prophase I each one gets
enveloped by a single layer of flat, follicular epithelial cells. (oocyte + follicular epithelium =
primordial follicle). During atresia, most of the germ cells degenerate, even before birth. Few of
them develop into larger cells called primary oocytes which enter prophase of meiosis I during fetal
development but do not complete the phase until after puberty. With the onset of the meiosis the
designation of the germ cells changes. They are now called primary oocytes. During the
developmental stages, each primary oocyte is surrounded by a single layer of flat follicular cells.
This structure is called a primordial follicle. The ovarian cortex that surrounds the primordial
follicle are made up of collagen fibers and stromal cells which are similar to fibroblasts. At birth,
about 200,000 to 2,000,000 primary oocytes are in each ovary. At puberty, about 40,000 of these
cells still exist and around 400 will mature and ovulate during their lifetime. The rest of the primary
oocytes undergo atresia.
Each month after puberty, gonadotropins (FSH and LH) are secreted by the anterior
pituitary gland which further stimulate the development of several primordial follicles. However,
only one will typically reach the maturity level for ovulation. A few primordial follicles grow to
become primary follicles which consists of a primary oocyte that is surrounded by several layers
of granulosa cells. The outermost granulose cells rest on a basement membrane. As the primary
follicle grows, it forms the zona pellucida, a clear glycoprotein layer between the primary oocyte
and the granulosa cells. Another layer called the theca folliculi forms from the surrounding
stromal cells of the basement membrane.
With maturation, a primary follicle becomes a secondary follicle. In a secondary follicle,
the theca differentiates into 2 layers: the theca interna and the theca externa. The theca interna is
layer made up of highly vascularized cuboidal secretory cells that secrete estrogen. The theca
externa is an outer layer of stromal cells and collagen fibers. The granulosa cells also begin to
secrete follicular fluid. This fluid is held in a cavity in the center of the secondary follicle called the
antrum. The innermost layer of granulose cells becomes attached to the zona pellucida and is
now called the corona radiata.
When primary follicles survive, secondary follicles with follicular epitheliums encompassing
multiple rows are engendered. This is now called the stratum granulosum. In the secondary
follicles a glycoprotein layer, the pellucid zone, between the oocyte and follicular epithelium
becomes visible. Cytoplasmic processes of the granulosa cells that lie upon it reach the oocyte
through the pellucid zone and thereby assure their maintenance function. Outside the basal
lamina the stroma ovarii organizes itself to become theca folliculi cells.
If the secondary follicles survive, tertiary follicles are engendered. Their identifying
characteristic is a fluid-filled cavity, the antral follicle. The oocyte lies at the edge in a mound
made of granulosa epithelial cells, the cumulus oophorus. In the meantime it has grown so large
that its cellular nucleus has attained the size of a whole primordial follicle. The connective tissue
around the follicle has already clearly differentiated itself into a theca interna, well supplied with
capillaries, out of large, lipid-rich cells (hormone production) and a theca externa, which forms a
transition to the stroma ovarii and contains larger vessels
Decisive for a successful follicle growth is a well-developed net of capillaries in the theca
interna. The precise steering mechanism that leads to the selection of a follicle and its subsequent
maturation to become a graafian follicle is still unknown. A Graafian follicle is an especially large
tertiary follicle that can be used in ovulation. Before ovulation a growth spurt of the tertiary follicles
takes place.
UTERINE TUBES:
There is a pair of long narrow ducts located in the human female one on each side called
the fallopian (uterine) tubes. They transport the sperm cells to the egg and the egg from the
ovary to the uterus (the womb). The Fallopian tubes provide a suitable environment for fertilization
and have small hair-like projections called cilia on the cells of the lining. These tubal cilia are
essential to the movement of the egg through the tube into the uterus. If the tubal cilia are
damaged by infection, the egg may not get 'pushed along' normally but may stay in the tube.
The uterine (Fallopian) tubes extend laterally from both upper lateral regions of the uterus.
Each has four regions (medial to lateral): the interstitial or intramural portion, the isthmic
portion, the ampulla, and the infundibulum. The lateral regions, the ampulla and "fimbria"
resembling the shape of a trumpet, swing freely usually hanging adjacent to the ovary. The uterine
tube is supplied by the branches of the uterine and ovarian vessels.
The uterine tubes are situated in the upper margin of the broad ligament, and extending
from the superior angle of the uterus to the side of the pelvis. Each fallopian tube is 10–13 cm (4–5
inches) long and 0.5–1.2 cm (0.2–0.6 inch) in diameter. Each tube is described as consisting of
three portions: (1) the isthmus; (2) the ampulla; and (3) the infundibulum with its abdominal
ostium, surrounded by fimbriae, one of which, the ovarian fimbria is attached to the ovary. The
channel of the tube is lined with a layer of mucous membrane that has many folds and papillae—
small cone-shaped projections of tissue. Over the mucous membrane are three layers of muscle
tissue; the innermost layer has spirally arranged fibres, the middle layer has circular fibres, and the
outermost sheath has longitudinal fibres that end in many fingerlike branches (fimbriae) near the
ovaries, forming a funnel-shaped depository called the infundibulum. The infundibulum catches
and channels the released eggs; it is the wide distal (outermost) portion of each fallopian tube. The
endings of the fimbriae extend over the ovary; they contract close to the ovary’s surface during
ovulation in order to guide the free egg. Leading from the infundibulum is the long central portion of
the fallopian tube called the ampulla. The isthmus is a small region, only about 2 cm (0.8 inch)
long, that connects the ampulla and infundibulum to the uterus. The final region of the fallopian
tube, known as the intramural, or uterine, part, is located in the top portion (fundus) of the uterus;
it is a narrow tube continuous with the isthmus, and it leads through the thick uterine wall to the
uterine cavity, where fertilized eggs normally attach and develop. The channel of the intramural
duct is the narrowest part of the fallopian tube. In connection with the fimbriae of the uterine tube,
or with the broad ligament close to them, there are frequently one or more small pedunculated
vesicles. These are termed the appendices vesiculosae.
The uterine tube consists of three coats: serous, muscular, and mucous. The external
or serous coat is peritoneal. The middle or muscular coat consists of an external longitudinal
and an internal circular layer of non-striped muscular fibers continuous with those of the uterus.
The internal or mucous coat is continuous with the mucous lining of the uterus, and, at the
abdominal ostium of the tube, with the peritoneum. It is thrown into longitudinal folds, which in the
ampulla are much more extensive than in the isthmus. The lining epithelium is columnar and
ciliated. This form of epithelium is also found on the inner surface of the fimbriae, while on the outer
or serous surfaces of these processes the epithelium gradually merges into the endothelium of the
peritoneum.
Fertilization of the ovum is believed to occur in the tube, and the fertilized ovum is then
normally passed on into the uterus; the ovum, however, may adhere to and undergo development
in the uterine tube, giving rise to the commonest variety of ectopic gestation. In such cases the
amnion and chorion are formed, but a true decidua is never present; and the gestation usually
ends by extrusion of the ovum through the abdominal ostium, although it is not uncommon for the
tube to rupture into the peritoneal cavity, this being accompanied by severe hemorrhage, and
needing surgical interference.
UTERUS:
The uterus (womb) is a hollow, thick-walled, muscular organ situated deeply in the pelvic
cavity between the bladder and rectum. It is the size and shape of an inverted pear. Into its upper
part the uterine tubes open, one on either side, while below, its cavity communicates with that of
the vagina. The body of the uterus projects anteriorly and superiorly over the bladder in a position
called anteflexion. When the ova are discharged from the ovaries they are carried to the uterine
cavity through the uterine tubes. If an ovum be fertilized it imbeds itself in the uterine wall and is
normally retained in the uterus until prenatal development is completed, the uterus undergoing
changes in size and structure to accommodate itself to the needs of the growing embryo. It
functions to nourish and house the fertilized egg until the unborn child, or offspring, is ready to be
delivered. If implementation does not occur during the reproductive cycle, the uterus is the source
of menstrual flow. The uterine cavity opens into the vaginal cavity, and the two make up what is
commonly known as the birth canal.
The uterus measures about 7.5 cm. in length, 5 cm. in breadth, at its upper part, and
nearly 2.5 cm. in thickness; it weighs from 30 to 40 gm. It is divisible into two portions. On the
surface, about midway between the body and the cervix, is a slight constriction known as the
isthmus, and corresponding to this in the interior is a narrowing of the uterine cavity, the internal
os of the uterus. The external os is the interior of the narrow cervix. The portion above the isthmus
is termed the body, and below that, the cervix which opens to the vagina. The cervix is the lower
constricted segment of the uterus. It is somewhat conical in shape, with its truncated apex directed
downward and backward. A dome shape portion superior to the uterine tubes is called the fundus.
The fundus is convex in all directions, and covered by peritoneum. The body of the uterus
gradually narrows from the fundus to the isthmus.
There are 8 ligaments of the uterus: two lateral or broad, two uterosacral, two cardinal
ligaments and two round ligaments. Attached to the uterus from of the sacrum there is a
considerable amount of fibrous tissue and non-striped muscular fibers. This tissue makes up the
uterosacral ligaments, which lie on either side of the rectum and connect the sacrum to the
uterus. The broad ligaments pass from the sides of the uterus to the lateral walls of the pelvis.
Together with the uterus they form a septum across the female pelvis, dividing that cavity into two
portions. They are made up of double folds of peritoneum that attach the uterus to either side of
the pelvic cavity. The cardinal (lateral cervical) ligaments attach from the pelvic wall to the
cervix and the vagina and are located below the bases of the broad ligaments. The round
ligaments are two flattened bands between 10 and 12 cm. in length, situated between the layers
of the broad ligament in front of and below the uterine tubes. It follows along the inguinal canal to
the labia majora, in which it becomes lost. The round ligaments consist principally of muscular
tissue prolonged from the uterus and that hold the position of the uterus. However, they allow for
slight movement of the uterus, which could potentially result in a malpositioned uterus also known
as retroflexion.
The uterus is made up of three layers of tissue: the perimetrium, the myometrium and the
endometrium. The loose surrounding tissue in the outer layer is called the perimetrium. It is
composed of simple squamous epithelium and areolar connective tissue. It becomes the broad
ligament and forms a shallow pouch covering ht bladder called the vesicouterine pouch. This
pouch is found between the bladder and the uterus. It also forms a deep pouch called the
rectouterine pouch that is found between the uterus and the rectum. The middle layer of the uterus
is called the myometrium. The myometrium is the middle layer of the uterine wall consisting of
smooth muscle cells and supporting stromal and vascular tissue. During labor and childbirth, the
coordinated contractions of the myometrium help push the fetus form the uterus. The inner layer of
the uterus is the endometrium. The endometrium is the highly vascularized lining of the uterine
cavity. In all placental mammals, including humans, the endometrium builds a lining periodically
which is shed or reabsorbed if no pregnancy occurs. Shedding of the functional endometrial lining
is responsible for menstrual bleeding. It is divided into 2 layers the stratum functionalis, which
lines the uterine cavity and sloughs off during menstruation. The deeper layer is the stratum
basalis, which is permanent and creates a new stratum functionalis when the old one sloughs off
during menstruation.
The uterine arteries supply blood to the uterus, which branch off in a circular fashion in
the myometrium. Those branches are called arcuate arteries. Arcuate arteries then branch off
into radial arteries that do deeper into the myometrium. Just before the arteries enter the
endometrium they divide into two arterioles: straight arterioles and spiral arterioles. Straight
arterioles supply the nutrients and substances necessary for the stratum basalis to regenerate the
stratum functionalis. Spiral arterioles supply the stratum functionalis and change immensely during
the menstrual cycle. The uterine veins take blood away from the uterus into the internal iliac veins.
The cervix secretes mucus called cervical mucus, which is a mixture of water,
glycoprotein’s, lipids, enzymes, and inorganic salts. It is more hospitable for sperm during and near
ovulation. It protects the sperm from phagocytes and the hostile environment of the vagina and
uterus.
VAGINA:
The vagina is a canal in female mammals that receives the male reproductive cells, or
sperm, and is part of the birth canal during the birth process. In humans, it also functions as an
excretory canal for the products of menstruation. It extends from the vestibule to the uterus, and is
situated behind the bladder and in front of the rectum; Its length is 6 to 7.5 cm. along its anterior
wall, and 9 cm. along its posterior wall. It is constricted at its commencement, dilated in the middle,
and narrowed near its uterine extremity. To the recess behind the cervix the term posterior fornix
is applied, while the smaller recesses in front and at the sides are called the anterior and lateral
fornices.
The vagina consists of an internal mucous lining and a muscular coat separated by a
layer of erectile tissue. The mucous membrane is continuous above with that lining the uterus. Its
inner surface presents two longitudinal ridges, one on its anterior and one on its posterior wall.
These ridges are called the columns of the vagina and from them numerous transverse ridges or
rugae extend outward on either side. These rugae are divided by furrows of variable depth, giving
to the mucous membrane the appearance of being studded over with conical projections or
papillæ; they are most numerous near the orifice of the vagina, especially before parturition. The
epithelium covering the mucous membrane is of the stratified squamous variety. Vaginal rugae
permit expansion of the vaginal cavity. These tend to disappear in older women and in those
women who have borne children.
The vagina is an elastic, muscular canal with a soft, flexible lining that provides lubrication
and sensation. The vagina connects the uterus to the outside world. The vulva and labia form the
entrance, and the cervix of the uterus protrudes into the vagina, forming the interior end. The
vagina receives the penis during sexual intercourse and also serves as a conduit for menstrual flow
from the uterus as well as child birth. During childbirth, the baby passes through the vagina (birth
canal). The hymen is a thin membrane of tissue that surrounds and narrows the vaginal opening. It
may be torn or ruptured by sexual activity or by exercise. In most virgins, the external opening to
the vagina is partially closed by a thin fold of tissue known as the hymen. The hymen closes the
vaginal opening to the exterior vaginal orifice. The opening (vaginal orifice) is partially covered by
the labia majora.
VULVA:
The external female genitalia that surround the opening to the vagina is the vulva;
collectively these consist of the labia majora, the labia minora, clitoris, vestibule of the vagina, bulb
of the vestibule, and the glands of Bartholin. All of these organs are located in front of the anus and
below the mons pubis (the pad of fatty tissue at the forward junction of the pelvic bones). Its
development occurs during several phases, chiefly during the fetal and pubertal periods of time. As
the outer portal of the human uterus or womb, it protects its opening with the labia majora (large
lips) and the labia minora (small lips). The labia majora are two thick folds of skin running from
the mons pubis to the anus. The outer sides of the labia are covered with pigmented skin,
sebaceous (oil-secreting) glands, and after puberty, coarse hair. The inner sides are smooth and
hairless, with some sweat glands. Beneath the skin layer, there is mostly fatty tissue with some
ligaments, smooth muscle fibres, nerves, and blood and lymphatic vessels. They form the lateral
boundaries of the vulval or pudendal cleft, which receives the openings of the vagina and the
urethra. Each labium has two surfaces, an outer, pigmented and covered with strong, crisp hairs;
and an inner, smooth and beset with large sebaceous follicles. Between the two there is a
considerable quantity of areolar tissue, fat, and a tissue.
Mons Pubis is the rounded eminence in front of the pubic symphysis, is formed by a
collection of fatty tissue beneath the integument. It becomes covered with hair at the time of
puberty. The labia minora, two smaller folds of skin between the labia majora, surround the
vestibule of the vagina; they have neither fat nor hairs. The skin is smooth, moist, and pink and has
sebaceous and sweat glands. On either side of the orifice of the vagina, between which and the
labia majora they end; in the virgin the posterior ends of the labia minora are usually joined across
the middle line by a fold of skin, named the frenulum of the labia.
Directly beneath the mons pubis and between the labia majora is a small structure of
erectile tissue known as the clitoris. It is capable of some enlargement caused by increased blood
pressure during sexual excitement and is considered homologous (comparable in structure) to the
male penis, only on a much smaller scale. Unlike the penis, the clitoris does not contain the
urethra for excretion of urine; it does have a rounded elevation of tissue at the tip known as the
glans clitoridis. Surrounding the glans clitoridis on two sides are the beginning folds of the labia
minora. These folds are known as the prepuce (or foreskin) of the clitoris. Like the glans penis,
the glans clitoridis contains nerve endings and is highly sensitive to tactile stimulation.
The cleft between the labia minora and behind the glans clitoris is named the vestibule of
the vagina: in it are seen the urethral and vaginal orifices and the openings of the ducts of the
greater vestibular glands. Many mucous glands are also present in the vestibular region. Both
the labia minora and labia majora tend to cover the vestibule. The external urethral orifice is
placed about 2.5 cm. behind the glans clitoris and immediately in front of that of the vagina; it
usually assumes the form of a short, sagittal cleft with slightly raised margins. The vaginal orifice
is a median slit below and behind the opening of the urethra; its size varies inversely with that of
the hymen. The Bulb of the Vestibule consists of two elongated masses of erectile tissue,
placed one on either side of the vaginal orifice and it becomes engorged with blood during sexual
arousal, narrowing the vaginal orifice. Each lateral mass measures a little over 2.5 cm. in length.
Their posterior ends are expanded and are in contact with the greater vestibular glands. The
Greater Vestibular Glands consist of two small, roundish bodies of a reddish-yellow color,
situated one on either side of the vaginal orifice in contact with the posterior end of each lateral
mass of the bulb of the vestibule. This gland produces a small quantity of mucus during
intercourse and provides lubrication. Embedded in the walls of the urethra are mucus secreting
glands called the paraurethral glands. The vulva has a sexual function; these external organs are
richly innervated and provide pleasure when properly stimulated. The vulva also contains the
opening of the female urethra, thus it serves for the vital function of passing urine.
PERINEUM:
The interval between the posterior commissure and the anus, from 2.5 to 3 cm. in length,
constitutes the perineum. It is diamond-shaped medial to the thighs and buttocks and it contains
the external genitals and anus. It is bound by the pubic symphysis, the ischial tuberosities and by
the coccyx. The perineum can be divided into the urogenital triangle that contains the external
genitalia and the anal triangle that contains the anus.
MAMMARY GLANDS:
The Mammary glands are modified sweat glands that secrete milk and are accessory
glands of the generative system in the breasts. Mammary glands are regulated by the endocrine
system and become functional in response to the hormonal changes associated with parturition.
They exist in the male as well as in the female. In the female they are two large hemispherical
eminences lying within the superficial fascia and situated on the front and sides of the chest
composed of dense irregular connective tissue. They increase during pregnancy and especially
after delivery, and become atrophied in old age. The left mamma is generally a little larger than the
right. In the mammary gland there are about 15 to 20 lobes separated by tissue. In each lobe are
several smaller compartments called lobules, which are made up of grapelike clusters of milksecreting glands called alveoli. Milk is excreted with the contraction of the myoepithelial cells that
surrounds the alveoli. The milk goes from the mammary glands it goes from the alveoli to the
secondary tubules and then into the mammary ducts. The mammary ducts also make up the
lactiferous sinuses where some milk may be stored before draining into the ducts.
The nipple is a cylindrical or conical pigmented eminence situated about the level of the
fourth intercostal space. It is capable of undergoing a sort of erection from mechanical excitement,
a change mainly due to the contraction of its muscular fibers. Circular and radiating muscles in the
areola, a circular disk of roughened pigmented skin surrounding the nipple, cause the nipple to
become firm and erect upon tactile stimulation; this facilitates suckling. The areola also contains
sebaceous glands to provide lubrication for the nipple during nursingIt is of a pink or brownish hue,
its surface wrinkled and provided with secondary papillæ; and it is perforated by from fifteen to
twenty orifices, the apertures of the lactiferous ducts. The base of the mammary papilla is
surrounded by an areola. Near the base of the papilla, and upon the surface of the areola, are
numerous large sebaceous glands, the areolar glands, which become much enlarged during
lactation (synthesis, secretion, and ejection of milk) and present the appearance of small tubercles
beneath the skin. These glands secrete a peculiar fatty substance, which serves as a protection to
the integument of the papilla during the act of sucking.