28.2 Female Reproductive System
Functions of the Female Reproductive System
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The ovaries produce secondary oocytes and hormones, including progesterone and estrogens
(female sex hormones), inhibin, and relaxin.
The uterine tubes transport a secondary oocyte to the uterus and normally are the sites where
fertilization occurs.
The uterus is the site of implantation of a fertilized ovum, development of the fetus during
pregnancy, and labor.
The vagina receives the penis during sexual intercourse and is a passageway for childbirth.
The mammary glands (part of the integumentary and reproductive system) synthesize, secrete,
and eject milk for nourishment of the newborn.
Overview of Organs
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include the ovaries (female gonads); the uterine (fallopian) tubes, or oviducts; the uterus; the
vagina; and external organs, which are collectively called the vulva, or pudendum.
The mammary glands are considered part of both the integumentary system and the female
reproductive system
Ovaries (Female Gonads)
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paired, oval glands that resemble unshelled almonds in size and shape
women are born with a fixed number of immature ova
Location: one on either side of the uterus
homologous to the testes of the male reproductive system (same embryonic development)
Functions: produce
a. (1) gametes, secondary oocytes that develop into mature ova (eggs) aft er fertilization
b. (2) hormones, including progesterone and estrogens (the female sex hormones), inhibin,
and relaxin
Ligaments of the Ovaries
a. Broad Ligament: a fold of the parietal peritoneum that attaches to the ovaries by a
double-layered fold of peritoneum called the mesovarium
b. Ovarian Ligament: anchors the ovaries to the uterus
c. Suspensory Ligament: attaches ovaries to the pelvic wall
Hilum: the point of entrance and exit for blood vessels and nerves along which the mesovarium
is attached.
Histology of the Ovary
a. Ovarian Mesothelium: a layer of simple cuboidal or squamous epithelium that covers
the surface of the ovary.
b. Tunica Albuginea: a whitish capsule of dense irregular connective tissue located
immediately deep to the ovarian mesothelium
c. Ovarian Cortex: region deep to the tunica albuginea that consists of ovarian follicles
surrounded by collagen fibers and fibroblast-like cells called stromal cells
d. Ovarian Medulla: region deep to the ovarian cortex that contains blood vessels,
lymphatic vessels, and nerves
e. Ovarian follicles: found in the cortex, where they consist of oocytes and a single layer of
surrounding cells called follicular cells, which later turn into granulose cells when there
are several layers of follicular cells later in development; surrounding cells nourish the
developing oocyte and begin to secrete estrogens as the follicle grows larger
f. Mature (graafian) Follicle: a large, fluid-filled follicle that is ready to rupture and expel
its secondary oocyte (ovulation )
g. Corpus Luteum: contains the remnants of a mature follicle aft er ovulation and produces
progesterone, estrogens, relaxin, and inhibin until it degenerates into fibrous scar tissue
called the corpus albicans
Oogenesis and Follicular Development
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Oogenesis: The formation of gametes (sex cells) in the ovaries
Oogenesis vs Spermatogenesis: oogenesis begins in females before they are even born, while
spermatogenesis begins at puberty; both occur via meiosis (germ cells undergo maturation)
Oogenesis Process
a. During early fetal development, primordial (primitive) germ cells migrate from the yolk
sac to the ovaries, where germ cells diff erentiate within the ovaries into oogonia
(diploid (2n) stem cells that divide mitotically to produce millions of germ cells)
b. Before birth, most of these cells degenerate via a process called atresia, while others
develop into larger primary oocytes that enter prophase of meiosis I during fetal
development but do not complete that phase until after puberty
c. During this arrested stage of development, each primary oocyte is surrounded by a
single layer of flat follicular cells to make a primordial follicle. The cortex contain
surrounding the follicle contains collagen fibers and fibroblast-like stromal cells
d. Each month aft er puberty until menopause, gonadotropins (FSH and LH) secreted by
the anterior pituitary further stimulate the development of several primordial follicles
(only one will typically reach the maturity needed for ovulation)
e. primordial follicles start to grow, developing into primary follicles, which consist of a
primary oocyte surrounded by granulose cells
f. As the primary follicle grows, it forms a clear glycoprotein layer called the zona pellucida
between the primary oocyte and the granulosa cells. stromal cells surrounding the
basement membrane begin to form an organized layer called the theca folliculi
g. With continuing maturation, a primary follicle develops into a secondary follicle, in
which the theca differentiates into two layers: (1) the theca interna, a highly
vascularized layer that secrete estrogens, and (2) the theca externa, an outer layer of
stromal cells and collagen fibers.
h. the granulosa cells begin to secrete follicular fluid, which builds up in a cavity called the
antrum in the center of the secondary follicle
i. The innermost layer of granulosa cells becomes firmly attached to the zona pellucida
and is now called the corona radiate
j. The secondary follicle eventually becomes larger, turning into a mature (graafian)
follicle, and just before ovulation, the diploid primary oocyte completes meiosis I,
producing two haploid (n) cells of unequal size—each with 23 chromosomes
i.
The smaller cell produced by meiosis I (first polar body) is essentially a packet of
discarded nuclear material.
ii.
The larger cell, known as the secondary oocyte, receives most of the cytoplasm
k. Once a secondary oocyte is formed, it begins meiosis II but then stops in metaphase.
The mature (graafian) follicle soon ruptures and releases its secondary oocyte (a process
known as ovulation) into the pelvic cavity together with the first polar body and corona
radiata
l. Normally these cells are swept into the uterine tube. If fertilization does not occur, the
cells degenerate. If sperm are present in the uterine tube and one penetrates the
secondary oocyte, however, meiosis II resumes.
i.
The secondary oocyte splits into two haploid cells, again of unequal size. The
larger cell is the ovum, or mature egg; the smaller one is the second polar body
ii.
The nuclei of the sperm cell and the ovum then unite, forming a diploid zygote.
If the first polar body undergoes another division to produce two polar bodies,
then the primary oocyte ultimately gives rise to three haploid polar bodies,
which all degenerate, and a single haploid ovum. Thus, one primary oocyte gives
rise to a single gamete (an ovum).
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By contrast, recall that in males one primary spermatocyte produces four
gametes (sperm).
Uterine (Fallopian) Tubes
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site of fertilization)
lie within the folds of the broad ligaments of the uterus; sides of the uterus
provide a route for sperm to reach an ovum and transport secondary oocytes and fertilized ova
from the ovaries to the uterus
infundibulum: the funnel-shaped portion of each tube; near the ovary, but opens to the pelvic
cavity; allows the uterine tubes to extends medially and inferiorly and attach to the superior
lateral angle of the uterus
contain fimbriae (fingerlike projections) that push the ova into the tube
a. Aft er ovulation, local currents are produced by movements of the fimbriae, which
sweep the ovulated secondary oocyte from the peritoneal cavity into the ampulla of the
uterine tube, where a sperm cell encounters and fertilizes it
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b. Some hours after fertilization, the nuclear materials of the haploid ovum and sperm
unite to become a zygotes and begins to undergo cell divisions while moving toward the
uterus
c. Fertilization is the unison of the ovum and sperm cell
d. Zygote: a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum
ampulla: widest, longest portion where sperm cells encounter and fertilize a secondary oocyte
isthmus: medial, thick-walled portion that joins the uterus
Histology
a. mucosa: consists of epithelium
i.
ciliated simple columnar cells: function as a “ciliary conveyor belt” to help move
a fertilized ovum (or secondary oocyte) within the uterine tube toward the
uterus
ii.
peg cells: nonciliated cells that have microvilli and secrete a fluid that provides
nutrition for the ovum)
iii.
lamina propria (areolar connective tissue).
b. Muscularis: middle layer composed of an inner, thick, circular ring of smooth muscle and
an outer, thin region of longitudinal smooth muscle
i.
Peristaltic contractions of the muscularis and the ciliary action of the mucosa
help move the oocyte or fertilized ovum toward the uterus
c. The outer layer of the uterine tubes is a serous membrane, the serosa
Uterus aka “the Womb”
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the body of the uterus projects anteriorly and superiorly over the urinary bladder in a position
called anteflexion
a. retroflexion (posterior tilting of the uterus) is harmless and without cause
Functions
a. serves as part of the pathway for sperm deposited in the vagina to reach the uterine
tubes
b. the site of implantation of a fertilized ovum, development of the fetus during
pregnancy, and labor
c. serves as the source of menstrual flow when implantation does not occur
Anatomy of the Uterus
a. Location: found between the urinary bladder and the rectum
b. larger in females who have recently been pregnant
c. smaller (atrophied) when sex hormone levels are low, as occurs aft er menopause
d. fundus: superior to the uterine tubes
e. body: central portion
f. cervix: inferior narrow portion that opens into the vagina
g. Isthmus: Between the body of the uterus and the cervix
h. Uterine Cavity: interior of the body of the uterus
i. cervical canal: interior of the cervix
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opens into the uterine cavity at the internal os
ii.
opens into the vagina at the external os.
j. Several ligaments that are either extensions of the parietal peritoneum or fibromuscular
cords maintain the position of the uterus and allow the uterine body enough movement
to the point where the uterus may become malpositioned
i.
paired broad ligaments: double folds of peritoneum attaching the uterus to
either side of the pelvic cavity
ii.
paired uterosacral ligaments: lie on either side of the rectum and connect the
uterus to the sacrum
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cardinal (lateral cervical) ligaments: inferior to the bases of the broad ligaments
and extend from the pelvic wall to the cervix and vagina
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The round ligaments are between the layers of the broad ligament; they extend
from a point on the uterus just inferior to the uterine tubes to a portion of the
labia majora of the external genitalia.
Histology of the Uterus
a. Perimetrium (the outer layer)
i.
Laterally, it becomes the broad ligament.
ii.
Anteriorly, it covers the urinary bladder and forms a shallow pouch, the
vesicouterine pouch
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Posteriorly, it covers the rectum and forms a deep pouch between the uterus
and rectum (rectouterine pouch or pouch of Douglas)—the most inferior point
in the pelvic cavity
b. Myometrium (middle layer): During labor and childbirth, coordinated contractions of
the myometrium in response to oxytocin from the posterior pituitary help expel the
fetus from the uterus.
c. Endometrium (inner layer): highly vascularized layer with ciliated and secretory
epithelium, underlying endometrial stroma in the lamina propria, and endometrial
(uterine) glands that develop as invaginations of the luminal epithelium and extend
almost to the myometrium
i.
Stratum Functionalis (functional layer) lines the uterine cavity and sloughs off
during menstruation.
ii.
the stratum basalis (basal layer), is permanent and gives rise to a new stratum
functionalis aft er each menstruation
Blood Supply: comes from branches of the internal iliac artery called uterine arteries
a. Arcuate Arteries: circulate the myometrium and branch into radial arteries
b. Radial Arteries: penetrate deeply into the myometrium
c. Just before the branches enter the endometrium, they divide into two kinds of
arterioles:
i.
Straight arterioles supply the stratum basalis with the materials needed to
regenerate the stratum functionalis
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spiral arterioles supply the stratum functionalis and change markedly during the
menstrual cycle.
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d. Blood leaving the uterus is drained by the uterine veins into the internal iliac veins.
e. Functions of Blood Supply
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support regrowth of a new stratum functionalis after menstruation
ii.
implantation of a fertilized ovum
iii.
development of the placenta
Cervical Mucus: a mixture of water, glycoproteins, lipids, enzymes, and inorganic salts produced
by the secretory cells of the cervix
a. can either be more hospitable to sperm at or near the time of ovulation because it is
then less viscous and more alkaline (pH 8.5) OR more viscous, forming a cervical plug
that physically impedes sperm penetration
b. supplements the energy needs of sperm
c. both the cervix and cervical mucus protect sperm from phagocytes and the hostile
environment of the vagina and uterus
d. may also play a role in capacitation: causes a sperm cell’s tail to beat even more
vigorously, and it prepares the sperm cell’s plasma membrane to fuse with the oocyte’s
plasma membrane so it can fertilize a secondary oocyte
Vagina
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a long, tubular fibromuscular canal lined with mucous membrane that extends from the exterior
of the body to the uterine cervix; between the urinary bladder and the rectum
receptacle for the penis during sexual intercourse, the outlet for menstrual flow, and the
passageway for childbirth
fornix: surrounds the vaginal attachment to the cervix
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