HUMAN REPRODUCTION BIOLOGY 269

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HUMAN REPRODUCTIONBIOLOGY 269
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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

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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 , has all of the
oocytes. One or two of these oocytes may be
developing before ovulation undeveloped ones are
stored here. Also contains the remnant from the
previous cycles ovulation, called a
, which secretes progesterone to
keep uterus ready for implantation of the embryo
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Maturation of an oocyte is called oogenesis,
which leads to ovulation

• During oogenesis, the oocyte is surrounded by
  follicular cells granulosa cells in one or more
  layers, forming a .

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The developing oocyte and its follicleFour
stages before ovulation

• 1.
  
• 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

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The developing oocyte and its follicleFour
stages before ovulation

• 2.
• Develop only after puberty 3 to 4 enter this
  stage each cycle
• No change in primary oocyte
• Follicle has begun development cells are
  larger

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The developing oocyte and its follicleFour
stages before ovulation

• 3.
  
• 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
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The developing oocyte and its follicleFour
stages before ovulation

• 4.
  .
• 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
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Big Question How is this process of oogenesis
regulated?
Oogenesis, as well as ovulation and many other
things, is regulated by the pituitary gland,
which lies just below the brain
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Oogenesis and growth of the follicle in the ovary
are initiated and stimulated by
from the
pitutitary
During this oogenesis under the stimulation of
FSH, follicular cells surrounding the oocyte
secrete the hormone , 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.
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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.

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Ovulation is triggered when the pituitary gland
secretes a different hormone, called
.
Luteinizing hormone also causes the follicular
cells of the now empty follicle to develop into
a . This structure
secretes the hormone
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Before ovulation FSH stimulates cells of
follicle to secrete ,
which stimulates the lining of the uterus to
develop.After ovulation LH stimulates cells of
the corpus luteum to secrete
, which maintains the uterine lining in this
ready for pregnancy condition
If fertilization and pregnancy occur, the
placenta of the embryo secretes a hormone called
, which
stimulates the corpus luteum to keep secreting
progesterone, which in turn keeps the lining of
the uterus thick and full of blood vessels.
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.
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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.
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Oviduct
Lateral End Wide opening, or
, surrounds the surface of the ovary. The
edge is surrounded by finger-like
. Middle Part Wide
Medial End Narrow leads into
uterus. Cavity of oviduct is continuous with
cavity of uterus
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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.
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Uterus

• Anterior to rectum Posterior superior to
  bladder

Narrowed inferiorly to form cervix, which
projects into vagina
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Uterus

• Outer layer
  Thick layer of muscle
• Inner layer
  Lots of glands blood vessels

Two layers of endometrium
Closer to myometrium Remains after
menstruation Regrows functional layer
Closer to cavity Thickens
every cycle Embryo implants here during
pregnancy Dies and falls off during
menstruation
Inferior end narrows to form , which
projects down into vagina
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Mass of Uterus

• Immediately before menstruation 100 150
  grams
• Immediately after end of menstruation 50
  100 grams
• End of pregnancy 1,000 1,500 grams

At end of pregnancy Uterus extends from vagina
inferiorly to bottom of sternum superiorly Lies
anterior to all other abdominal organs except
bladder
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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
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External Genitalia
The vagina opens between the into a space
called the
Outside of those are the
At the anterior junction of the outer labia is the
Note that
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The head, or glans, of the

clitoris which is visible externally

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.
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Lateral to uterus
Oviduct
Ovary
Uterus
Pubic Bone
Bladder
Rectum
Clitoris
Labium minora
Vagina
Labium majora
Urethra
x