Functions of the Female Reproductive System
Produce hormones (estrogen and progesterone) for secondary
sexual characteristics.
Produce one large oocyte at regular intervals and release it in such
a way that it enters the oviduct (“Fallopian tube”,“uterine tube”).
Receive semen from the male and transport it into the oviduct.
Produce hormones (estrogen and progesterone) which prepare the
uterus for pregnancy each cycle by thickening its inner lining;
Getting rid of this thickened lining each cycle if pregnancy does
not occur.
Protect and nourish the embryo and fetus during pregnancy, then
expel it through the vagina
Produce milk to nourish the newborn
Organs of the female
reproductive system
Let’s start with the Ovary:
Located within pelvis, 2 to 5 cm (1 to 2 inches) lateral to the uterus
Approximately 3cm x 2cm x 1cm
Central region, or “medulla”, consists of connective tissue with
many blood vessels.
Outer region, or “cortex”, has all of
the follicles within which oocytes
develop and are ovulated.
Maturation of an oocyte is called
oogenesis, which leads to ovulation
(release of the oocyte from the ovary)
During oogenesis, the
oocyte is surrounded by
one or more layers of
follicular cells (also called
granulosa cells) forming a
follicle
The developing oocyte and its follicle:
Four stages before ovulation
1. Primordial Follicles:
All formed before birth - hundreds in each ovary
Have not yet begun development – remain dormant until puberty
Consists of primary oocyte surrounded by a single layer
of flat follicular cells
The developing oocyte and its follicle:
Four stages before ovulation
2. Primary Follicles:
Develop only after puberty; 3 to 4 enter this stage each cycle
No change in primary oocyte
Follicle has begun development – cells are larger
The developing oocyte and its follicle:
Four stages before ovulation
3. Secondary Follicles:
1 or 2 primary follicles progress to this stage each cycle
Primary oocyte larger, finishes
first division of meiosis to
become a secondary oocyte,
also forming a polar body.
Follicle grows larger as
follicular cells divide to form
many layers; spaces begin to
develop in center of follicle
The developing oocyte and its follicle:
Four stages before ovulation
4. Mature or Vesicular Follicle
Most follicles which made it to “secondary” will reach this stage
Follicle is very large; Many layers of cells surrounding fluid-filled
center called antrum
Secondary oocyte covered
with thick, clear membrane
called zona pellucida;
pushed to one side in
follicle and surrounded by
mass of follicular cells
called cumulus oophorus
Big Question: How is this process of oogenesis regulated?
Oogenesis and growth of the follicle are regulated by the pituitary
gland, which lies just below the brain
The next stages, ovulation and formation of a corpus luteum,
will also be controlled by the pituitary gland.
Oogenesis and growth of the follicle in
the ovary are stimulated by follicle
stimulating hormone (FSH) from the
pituitary
During oogenesis under the stimulation
of FSH, follicular cells surrounding the
oocyte secrete the hormone estrogen,
which stimulates the inner lining of the
uterus to thicken and begin secreting
mucus, getting ready for pregnancy
This estrogen from the follicular cells also inhibits the pituitary
gland from secreting any more FSH.
Thus, no more follicles will be stimulated to develop until it stops.
Rupture of the follicle is ovulation.
The secondary oocyte, surrounded by the zona pellucida and
cumulus oophorus, is released from the surface of the ovary,
where it can be captured by the open end of the oviduct.
The cumulus oophorus now called the corona radiata.
Ovulation is triggered when the pituitary gland increases its
secretion of a different hormone, called luteinizing hormone.
Luteinizing hormone also causes
the follicular cells of the now
empty follicle to develop into a
corpus luteum. This structure
secretes the hormone
progesterone, which inhibits the
secretion of luteinizing hormone
from the pituitary gland
Before ovulation: Cells of follicle secrete estrogen, which stimulates
the lining of the uterus to develop.
After ovulation: Cells of the corpus luteum secrete progesterone,
which maintains the uterine lining in this “ready for pregnancy”
condition
If fertilization and pregnancy do not occur, after a few days the corpus
luteum deteriorates and stops producing progesterone. Without its
stimulus, the uterus can not maintain its thick lining, so this falls off
and is shed as menstruation.
If fertilization and pregnancy occur, the placenta of the embryo
secretes a hormone called chorionic gonadotropin, which stimulates
the corpus luteum to keep secreting progesterone, which in turn
keeps the lining of the uterus thick and full of blood vessels.
When the oocyte is released from the surface of the ovary during
ovulation, it is picked up by the oviduct, or Fallopian Tube, a hollow
muscular tube which leads from near the uterus to the ovaries.
Oviduct or Fallopian Tube:
Lateral End: Wide opening, or infundibulum, surrounds the surface of
the ovary. The edge is surrounded by finger-like fimbria.
Middle Part: Wide ampulla
Medial End: Narrow
isthmus leads into uterus.
Cavity of oviduct is
continuous with cavity of
uterus
By mechanisms not completely understood:
The oviduct moves the oocyte toward the uterus
The oviduct moves sperm away from the uterus
Fertilization occurs in ampulla of oviduct, forming the zygote, which
goes through repeated mitotic cell divisions to eventually form the
embryo.
Oviduct moves this growing
mass of pre-embryo cells
toward uterus: takes 3 or 4
days.
Secretions from oviduct are
necessary to keep sperm,
oocyte, and embryo alive.
Uterus:
Anterior to rectum; Posterior & superior to bladder
Narrowed inferiorly to
form cervix, which
projects into vagina
Uterus:
Outer layer = Myometrium:
Thick layer of muscle
Inner layer = Endometrium: Lots of glands & blood vessels
Two layers of endometrium:
Basal layer: Closer to myometrium;
Remains after menstruation;
Regrows functional layer
Functional layer: Closer to cavity;
Thickens every cycle when
stimulated by estrogens;
Embryo implants here during
pregnancy;
Dies and falls off during menstruation
Mass of Uterus:
Immediately before menstruation:
100 – 150 grams
Immediately after end of menstruation: 50 – 100 grams
At end of pregnancy: 1,000 – 1,500 grams
Uterus extends from vagina inferiorly to bottom
of sternum superiorly
Lies anterior to all other abdominal organs
except bladder
Vagina:
Thin-walled, tubular
Inferior to uterus;
Anterior to rectum
Posterior to bladder & urethra
Receives penis and semen
during sexual intercourse
Passage for delivery of fetus or
menstrual flow
External Genitalia:
The vagina opens between
the inner labia or labia
minora, into a space
called the vestibule.
Outside of those are the
outer labia or labia majora.
At the anterior junction of the
outer labia is the clitoris …
Note that the urethra also opens into the
vestibule, but the anus opens posterior to it.
The head, or glans, of the
clitoris which is visible is only
a small part of this organ.
Two shafts of erectile tissue
extend backwards along the
pelvic floor on either side of
the urethra and vagina.
These are the same erectile tissues located in
the penis of a male, called corpora cavernosa
Oviduct
Ovary
Lateral to
uterus
Uterus
Bladder
Pubic
Bone
Clitoris
Labium
minora
Vagina
Urethra
Labium majora
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